RTK Crops Up in Precision Agriculture

Take a look at the major manufacturers of multi-frequency GNSS equipment and the markets they serve. Obviously, surveying is an important market; construction is a major one too. Maybe you’ve noticed that agriculture is also making its way up the food chain, so to speak. Trimble, Topcon, Leica/Novatel, Deere/Navcomm, and Hemisphere GPS are all pursuing the precision agricultural market with RTK-like precision.

The terms “precision agriculture” and “precision farming” have been around for a long time. There are conferences dedicated solely to sharing information on this topic, such as the 9th International Conference on Precision Agriculture. The classic precision ag market has been relatively unchanged for the past decade or so. Yes, in the past few years WAAS (Wide Area Augmentation System) has made a substantial impact with respect to a reliable and convenient source of corrections for one-meter accuracy using GPS, but all in all, one-meter accuracy is what most precision ag users have adapted to.

Stepping back, GPS/GNSS is only one component of the precision agriculture puzzle. Remote sensing (aerial photography/LIDAR), various sensors, and GIS (geographic information systems) software all play a key role in enabling people to record, analyze, and apply data used to make decisions that optimize the output of a particular agricultural area.

There are a few keys areas where GPS/GNSS is used in agriculture, though. These aren’t all-inclusive, but cover significant tasks where GPS has been very beneficial.

1. Field mapping: there have always been field maps of some sort, whether they were hand-sketched or derived from an aerial photo, but GPS has improved the precision substantially. Not only can one map the perimeter of the field, but also infrastructure such as roads, drain tile, outlets, wells, buildings, etc. The farmer doesn’t necessarily do this, but fertilizer distributors have become GPS-savvy and offer this service.
2. Yield mapping: as crops are harvested, a GPS receiver connected to a yield monitor sensor records a coordinate along with the yield data. This data is combined and analyzed to create a map of how well different areas of the field are producing.
3. Guidance: when spreading fertilizer or planting, equipment operators have traditionally used markers such as foam or other visual aids to mark where they’ve been to try and avoid overlap. The assistance of GPS and onboard guidance systems, such as a light bar, can further reduce overlap.

As I mentioned before, for many years precision ag users have settled for one-meter precision. Companies like Hemisphere GPS (formerly CSI Wireless) did very well designing single-frequency GPS receivers for the precision ag market. Hemisphere is also a leading designer of radio beacon (Coast Guard) receivers. Radio beacons, in addition to WAAS, are a free source of corrections for one-meter accuracy. Trimble was also an early supplier of precision ag GPS receivers and related equipment, typically offering single-frequency products like the AG-132.

While the real-time kinematic (RTK) technique has been around since the early 90s, it didn’t gain wide acceptance in the precision ag industry. The accuracy was great, down to approximately 2 cm at the time, but the equipment was clunky. The user had to set up a reference station near the field he was working on. The communication link was complicated, and some types needed Federal Communications Commission (FCC) licensing. Consequently, there were several potential points of failure. Lastly, the cost for a complete RTK system (base, rover, and radios) was high, upwards of $50,000. It just wasn’t cost-effective.

What is an RTK Network?

It’s an ambiguous term, because it means different things depending on the industry, but essentially the hardware setup is the same no matter which industry we are discussing. An RTK network is a series of dual-frequency reference stations spaced optimally within a region so as to provide RTK corrections to subscribers within that region. Following is an illustration of an RTK network for agriculture in the Ohio area.

All the reference stations are surveyed (more on that below) with respect to one another.

The network subscriber is assigned a primary reference station to use. RTK networks for agriculture are single-baseline solutions; the subscriber can only use one reference station at a time. There is no “network solution” per se, or redundancy like there is in RTK networks used in the surveying and construction industries. Therefore, when a single reference station “goes down,” the subscribers in that area are down also. There is software available from RTK network vendors that allows the administrator to monitor all reference stations via the Internet, but some networks don’t have that feature implemented. In that case the administrator hears about problems when subscribers have problems.

Another major difference between RTK networks for agriculture and RTK networks for surveying and construction is the communication method. The latter primarily use data plans on mobile phones to receive corrections. Either the mobile phone is linked via Bluetooth to the receiver or a cellular modem is built inside the receiver.

RTK networks for agriculture, on the other hand, primarily use spread spectrum radios (900 Mhz band) to transmit corrections to the receiver. The benefit of a spread spectrum radio is that they are free to use and don’t require a license from the FCC to operate. They are limited in their broadcast range, however, which is typically two to three miles. To solve this problem, radio repeaters are used to extend the distance. Depending on the topography, as many as four repeaters may need to be permanently mounted to effectively cover the broadcast range needed, based on the spacing of the reference stations. Even then, there may still be some areas that are not fully covered. In that case, temporary mobile repeaters may be used to provide coverage to that area.

The Wild, Wild West of RTK Networks

Bill Henning, real-time specialist with the National Geodetic Survey (NGS), said it best: the recent explosion of RTK networks is like the Wild, Wild West. They are proliferating so quickly that it’s hard to keep track of them. One of his tasks is to help develop guidelines for RTK network operators, and I think NGS is making inroads into the survey/construction industry with their initiative. People are looking for that sort of guidance with respect to RTK network setup, as well as monitoring for the networks once they become operational.

RTK networks for agriculture seem less structured than in other disciplines, though, and administrators rely more heavily on vendor recommendations. For example, some are based on the ITRF reference frame, while others are based on some version of NAD83. Some networks hire land surveyors to establish their reference station locations, while others do it themselves using NGS’s OPUS program or other methods. Very few, I think, realize the resources available from the NGS, such as the Cooperative CORS program.

Separate Industries, Separate RTK Networks

Even this early in the RTK network game, the duplicity of networks between agriculture and survey/construction is interesting. For example, an RTK network for agriculture can cover the same area as an RTK network for survey/construction. In the state of Georgia, there are several RTK networks for agriculture and several for survey/construction, some of which overlap. In fact, one would think that these folks (ag and survey/construction) would consolidate their efforts. The RTK network equipment is virtually the same. But alas, the manufacturers don’t want this. Why not? To answer that question, just employ the old adage: follow the money.

The fact is that a farmer isn’t going to pay the same RTK network subscription rate that a surveyor or construction company will. The numbers are vastly different. The typical subscription rate for access to an agricultural RTK Network is $1,300 to $1,500 per unit per year. Subscription rates for access to a survey/construction RTK network are as high as $4,500 per unit per year.

Some industry folks say that aggressive subscription pricing is the reason RTK networks in the agriculture market have expanded rapidly in the past few years. A farm is very hesitant to pay $4,500 annually when they can select a service like OmniSTAR and pay $1,500 annually.

Again, there are differences between the networks used in agriculture and those in survey/construction; most, if not all, are software-related. RTK networks for survey/construction offer a true networked solution, where several reference stations are used to compute a correction, whereas RTK networks for ag are single-baseline solutions, like users would normally set up as a base rover for their own use.

Others at the Party

Of course, OmniSTAR (HP/XP),Deere (Starfire), and Novariant (AutoFarm) offer a GPS-based solution in the precision ag industry. They are not pure-play RTK solutions like RTK networks are, although they do have RTK capability. True RTK networks are capable of constantly delivering ~2 cm accuracy day-in and day-out. These folks going after the precision ag market offer decimeter-level services primarily (1 decimeter being the equivalent of 10 cm), and then RTK solutions when needed.

It will be interesting to see how pure-play RTK players respond as RTK networks for agriculture continue to expand … which they most certainly will.

From A to B with PND

I covered this subject a while back, but I think it’s time to revisit it. Personal navigation devices (PNDs) are still selling like crazy. If you don’t have one, someone you know does. Tens of millions of these things are being sold per year.

If you don’t have one yet, you’ve got some options, because you can take it as a tax deduction. Perhaps a bit of “consult your accountant” verbiage should go here, but any time you need to drive from Point A to Point B for your job, I think you can take it as a deduction. Even if you do pay full price, it’s still a bargain.

First of all, you must be aware of the explosion in the number of consumer navigation units recently — you know, the Garmins, TomToms, Magellans, Mios, and Navigons of the world. If you go to Best Buy, Fry’s, Circuit City — even Radio Shack — you’ll see a bazillion of them on the shelf.

Disregarding the personal benefits of having one, I think they are one of the biggest bangs for your buck today, in terms of job efficiency. With labor being so expensive, I don’t see how a company can afford not to have one of these in each rig that’s headed to a job site. How many times have you (or one of your crew) gotten lost trying to find a job site, the local Home Depot, an ATM, or whatever? You aren’t just wasting your own time by being lost; it has a ripple effect.

I agree that PNDs aren’t for everyone. The solo surveyor working in his or her hometown and immediate surrounding towns probably knows the area better than Rand McNally. I’m thinking more along the lines of a contractor (be it a survey company or whatever) that has multiple people going in and out of a project. Maybe some employees are commuting directly from their homes, some are coming from the office, etc.

I think it’s hard to measure the stress, time spent, and other impacts of figuring out directions when working in an area that is not well known to the driver. Ever since I started carrying a little GPS navigator with me, I’ve virtually stopped using MapQuest or worrying about dealing with directions of any sort. Maybe you’re not like me, where you want to have all directions planned out in advance so you can stick to a tight schedule. To accomplish that, part of my preparation once included printing out all the directions and maps from MapQuest. I don’t bother with any of that now.

Even if you don’t use the directions feature, you’ve got a complete, nationwide electronic map at your fingertips. You can zoom out, zoom in, and pan around the screen. Following are some sample screens:

 

Which One Is Best?

Well, it depends. I hate that answer when I hear it, but it’s true. But this shouldn’t lead to “analysis paralysis,” where you can’t decide what to do so you don’t do anything. For me, there are four general features that are important to consider, no matter which additional bells and whistles you desire:

1. Display size. There is nothing worse than having to squint and try to focus on a micro-map when you are supposed to be driving. I like a large (relatively speaking), bright display. There are a couple of very common display sizes: 3.5-inch and 4.3-inch. Of course, the larger the display is, the larger the overall unit size is (and usually, the more expensive). I think the tradeoff is worth it for the larger screen size.
2. Ruggedness and reliability. It’s no better than a rock on your dashboard if it doesn’t work. I hate the flip-up antennas. Not many of the newer units have those any longer, but some of the older ones do. They are begging to get snapped off, unless you leave them permanently mounted on your dash. Also, some of the windshield mounts are pretty hokey, so be aware. In general, the various cable connections should appear solid.
3. Battery life. I guess this one depends on how you are going to use it. Personally, I like to take it from my dash and throw it in my laptop bag when I’m traveling by air. I dislike battery chargers in general (a necessary evil in this business), so I prefer a unit that will operate for at least five hours on one charge so I don’t have to cart the charger around with me.
4. Spoken street names. This is called “text-to-speech.” You can live without it, but it’s a nice feature. Instead of telling you “turn right in 500 feet,” it says “turn right in 500 feet on Main Street.” The lower-priced models typically don’t have this option.

There are many, many other bells and whistles you might like, such as real-time traffic data, Bluetooth for hands-free phone use, MP3 players, an FM interface to your vehicle sound system, etc., but those are more a matter of personal preference.

As coordinate-centric people, a lot of surveyors and mappers like to use State Plane. Very few navigation units support this sort of feature, although some support loading USGS topo maps in the background. I’m of the mindset that you really don’t want to try to do too many things with a PND, though. Call it a navigator and let it go at that. If you want a more coordinate-centric unit, then you’ll have to buy something other than a PND, like a Garmin GPSMAP 60CSx, DeLorme PN-20, or Magellan Triton.

I’ve put together a partial list of units with different features. The links are generally to the manufacturers’ websites, so don’t use the prices listed there as a reference.

3.5″ Display Units

TomTom ONE 3rd Edition (2-hr battery life, no text-to-speech, street-priced under $200).

Garmin Nuvi 200 (up to 5-hr battery life, no text-to-speech, street-priced under $200).

Garmin Nuvi 260 (up to 5-hr battery life, text-to-speech, street-priced under $300).

Magellan RoadMate 1200 (2-hr battery life, no text-to-speech, street-priced under $200).

Magellan CrossoverGPS (8-hr battery life, text-to-speech, IPX-4 waterproof rating, can load USGS topos, street-priced under $300).

Mio C220 (4-hr battery life, no text-to-speech, street-priced under $200).

Mio C310x (4.5-hr battery life, text-to-speech, street-priced under $250).

4.3″ Display Units

TomTom ONE XL (2-hr battery life, no text-to-speech, street-priced around $200).

TomTom GO 920 (up to 5-hr battery life, text-to-speech, street-priced under $500).

Garmin Nuvi 200W (up to 5-hr battery life, no text-to-speech, street-priced under $200).

Garmin Nuvi 880 (up to 4-hr battery life, text-to-speech, street-priced under $1,000).

Magellan Maestro 4200 (up to 4-hr battery life, text-to-speech, street-priced under $400).

Magellan Maestro 4250 (up to 4-hr battery life, text-to-speech, street-priced under $500).

Mio C320 (4-hr battery life, no text-to-speech, street-priced under $200).

Mio C720t (up to 3-hr battery life, text-to-speech, street-priced under $400).

There are many other navigator units on the shelves at the store. I’ve just listed ones from the top four market leaders.

You’ll notice I didn’t mention anything about the software interface. There are many opinions floating around about Brand X interface being better than Brand Y. After using a lot of different PNDs, I think the argument is about the same as Brand X total station/GPS vs. Brand Y total station/GPS. Most have very similar functionality, and their own idiosyncrasies, so it’s just a matter of getting used to it. One thing is for sure: the user interfaces are all different.

Don’t be stymied by analysis paralysis. A PND is the sort of tool (or toy) that once you get used to it, you can’t imagine working without it. Remember when folks fought against the electronic data collector, back when it was first introduced?

Catching Up

There has been a lot of activity on both the civilian and military sides of GPS/GNSS these past few weeks. Instead of a central theme to this newsletter, I’m going to comment on three points of interest: a DoD directive regarding position, navigation, and timing; PRN32; and some new product developments.

New Department of Defense Directive

On February 19, 2008, the Deputy Secretary of the U.S. Department of Defense (DoD) issued Directive #4650.05, which addresses, among other things, the “policy, procedures and responsibilities” for GPS. Although there will be many who will dissect and analyze the Directive for weeks to come, it’s clear that civilian influence on GPS continues to rise. You can read our Military and Government Editor Don Jewell’s initial comments here.

Of interest to the survey/construction/mapping community is the fact that the Department of Transportation is specifically mentioned as a key external agency (external to the DoD) to have a say in GPS activities. The Department of Homeland Security and NATO were the other two key external agencies named.

There is nothing earth-shattering about the directive, but it certainly sends a strong message that the federal government wants the civilian community — domestic and perhaps more so, international — to feel more comfortable about GPS, even though it’s still a U.S. military program.

PRN32

After a few months of waffling and discussion and announcements, PRN32 was finally set healthy. It’s been ready to go, but there has been concern about the effect that it would have on GPS receiver firmware. It was suspected that some GPS receivers wouldn’t be able to handle it, or would be adversely affected by it, because they may interpret PRN32 as PRN00.

This isn’t the first time that DoD has used PRN32. PRN32 was used temporarily in the early 90s until it was discovered that some GPS receivers interpreted it as PRN 00. It hasn’t been used again until now, some 15 years later.

Chances are that your receiver should be able to handle PRN32, given the event back in the early 90s and the DoD memo released more than a year ago. The satellite in question was set healthy on February 26, 2008. If your receiver is tracking but still not using PRN32, it may be worth a call to the dealer or manufacturer of your equipment to see if there is a firmware update available.

Depending on your location, PRN32 may help you. I was in the field in the western United States a couple of weeks ago, for example (before PRN32 was set healthy). I was only using five GPS satellites with an RTK receiver while down in a hole, and my receiver was tracking PRN32. It was in a perfect part of the sky that would’ve probably allowed me to get the tough shot I wanted, had it been set to healthy at that time, but no dice. I’m going back to the same site in a few weeks, and I’ll be watching for it. The RTK receiver I was using is more than 10 years old, so it will be interesting to see how it handles a healthy PRN32.

Product Announcements

Normally, I leave the new product announcements out of the editorial area, but three recent ones deserve particular attention. I mentioned two of them, from Javad GNSS and Magellan, in my December column of who to look out for in 2008. Both companies have come through in short order.

Javad GNSS. Early last month, Dr. Javad Ashjaee — former Trimble engineer and founder of Ashtech, Javad Positioning Systems (which was sold to Topcon in 2000), and Javad Navigation Systems — introduced the world to products developed by his new venture: Javad GNSS. In true Javad style, he’s pushing the envelope on both the technical side and the business side of the equation.

Of course, it’s expected that Javad’s new product line would account for every signal available, and probably every one that is planned. No disappointment there. His Triumph technology sports 216 channels to track everything from GPS L1/L2/L5 to Europe’s E1/E5 Galileo to GLONASS L1/L2, as well as all SBAS signals. That’s no big news, though, as all the other major manufacturers offer similar products.

What’s new and unique about Javad’s offering is the “RTK Umbrella.” The concept makes sense. The idea behind the RTK Umbrella is to increase the reliability of RTK positioning. A cluster of four antennas (on the rover) is used to compute sixteen baselines for every RTK measurement. Here is what the umbrella looks like.

After looking at it, you’re probably thinking the same thing I am: How am I going to cart that thing around all day? The short answer is, you won’t. But I can see an application where one could use the RTK Umbrella for setting control and performing other geodetic functions that require a higher degree of reliability and integrity. Then, you could toss it into the back of the truck and just use the single antenna for the production work.

It’s an interesting concept. I’ve got to give the guy credit for being creative.

Magellan. Magellan has been noticeably quiet in the high-end, survey-grade survey business for quite a while. The roots of their high-end business came from Ashtech, which they acquired many years ago. Yes, they have the Z-Max.Net that they announced a couple of years ago, but in a world where multi-constellation GPS and GLONASS receivers are the norm, it’s a me-too product at best. To give credit where credit is due, Magellan has continued to dominate the lower-end L1 survey-grade receiver market with its ProMark series of receivers and more recently, its ProMark 3 RTK product.

Now, as the company has been threatening to do (albeit under its breath), it has placed both feet squarely back in the high-end survey receiver business with the ProMark 500, a multi-constellation receiver that places Magellan in the same class as the best Trimble, Topcon, and Leica receivers. Granted, there is not a lot of information available on the ProMark 500, other than the video on its website. The real test will be when Magellan starts to ship the product, and dealers and users begin to run it in production mode.

My guess is that the technology will be pretty good. I think one of the biggest challenges will be to rebuild their surveying distributor network. With Topcon and Leica buying up distributors like candy in the past twelve months, the pickin’s are getting pretty slim.

Trimble. Remember when the Trimble ProXRS was the cream of the sub-meter mapping crop of receivers? It was a L1 C/A code workhorse of the past decade around the world. Then, it faded away when the ProXT/ProXH receivers were introduced. But neither of those really replaced the ProXRS.

Now, Trimble has upped the ante by introducing the ProXRT. The ProXRT offers users a range of accuracy depending on their needs, from sub-meter down to decimeter (10cm) accuracy. Perhaps the most significant feature is that the ProXRT is capable of using the Russian GLONASS satellites as well as GPS. The product announcement implies that GLONASS signals are used when GPS satellite availability is impaired. I have two comments about GLONASS on mapping-grade receivers.

1. Unless you are using your own GPS/GLONASS reference station, the GLONASS signals used on a mapping-grade handheld will be uncorrected (autonomous). Virtually no CORS receivers have GLONASS capability; neither NDGPS nor WAAS/EGNOS use GLONASS. So, there are no free public correction sources for GLONASS like those we are used to with GPS. However, many RTK networks are broadcasting both GPS and GLONASS corrections.

 

1. Autonomous GLONASS measurements offer much worse accuracy than autonomous GPS measurements, by a factor of five. This is because of the inferior clock and ephemeris data.

However, if used in the right circumstances, tracking a GLONASS satellite(s) can be the difference between getting a measurement or no measurement at all — even if the accuracy of the position takes a hit.

Another feature that the ProXRT brings back, which was curiously missing from the ProXT and ProXH, is OmniSTAR capability. The ProXRT is capable of using OmniSTAR’s VBS, XP, or HP service. This, of course, means that the ProXRT is a GPS L1/L2 receiver.

I’ll be attending the annual ACSM Conference on Thursday of this week. I’ll keep my eyes open for any other new developments. I’ll probably blog or otherwise comment on the conference somewhere on the GPS World website, as that is becoming our modus operandi when attending conferences. I like that format, and it brings you a bit closer to what’s happening if you are unable to attend the conference yourself.

With nearly 60 GPS engineers and scientists, the Jet Propulsion Lab (JPL) is one of the biggest GPS R&D centers in the world today. It operates as a division of the California Institute of Technology (Caltech), which manages the lab for the National Aeronautics and Space Administration (NASA).

Among other things, JPL operates the Global Differential GPS (GDGPS) system, which sells technical services and data and licenses software. The GDGPS system within JPL employs a vast, worldwide network of more than 100 L1/L2 GPS reference stations owned by itself and its partners.

Each reference station streams GPS measurements back to the GDGPS Operations Centers once per second. Data is then processed and analyzed in real time. Talk about redundancy — each GPS satellite is always observed by at least ten reference stations, and twenty-five is typical. Read more

It’s easy to get lost in JPL’s wide array of GPS product and service offerings, so I’ll try to stick with the part that’s closest to survey and construction.

Among other activities, JPL has people dedicated to monitoring and modeling the atmosphere — especially the ionosphere, which strongly impacts GPS measurements. They provide real-time, global maps of the Total Electron Content (TEC) used for L1 differential corrections around the world (think SBAS like WAAS and MSAS) and also for predicting ionospheric storms.

Dr. Michael Whitehead of Satloc, Inc. (now a division of Hemisphere GPS, Inc.), lead the first Wide-Area Differential GPS (WADGPS) commercial ventures to license JPL’s clock/orbit correctors and iono modeling services. This was back in the mid-90s, and Satloc’s target market was agriculture. Remember, this was before Selective Availability (SA) was turned off, so without a source of corrections, horizontal GPS accuracy without augmentation would routinely blow out to 100 meters. With its system, Satloc was able to deliver sub-meter L1 corrections to users via communications satellite.

“They (JPL) provided core technology. It worked great. The accuracy was there,” said Whitehead.

Whitehead said Satloc operated its own GPS reference network and internal software for generating corrections, but it also used JPL’s service to provide system redundancy. The Satloc system was set up to use corrections from either system (Satloc or JPL), and could automatically switch between the two systems.

The Satloc network was eventually sold to Fugro/OmniSTAR, another WADGPS service provider that integrated JPL data into its product offering. Hemisphere GPS/Satloc products now rely on WAAS (Wide Area Augmentation System) for their source of corrections. WAAS is built on core JPL technology, a predecessor of the GDGPS software. According to Whitehead, WAAS is very similar to the system that Satloc originally developed.

Fugro/OmniSTAR

Fugro/OmniSTAR operates its own GPS reference station network (over 100 worldwide, with 21 of those in North America) and has offered a WADGPS service in certain regions of the world dating back to the late 80s on a subscription basis. Until the late 90s, OmniSTAR/Fugro was a “one-trick pony,” offering a sub-meter “VBS” service for L1 GPS receivers. This is based on its worldwide network of GPS reference stations. Since then, the company has expanded its services in response to demand for greater accuracy and system redundancy.

Now, Fugro/OmniSTAR offers two additional levels of service: HP and XP. Both require the user to have a dual-frequency receiver (L1/L2). The upside is that the HP service provides +/-10cm horizontal accuracy using carrier phase (a sort of float solution). The HP service is based on Fugro/OmniSTAR’s proprietary GPS reference network and software. HP service is available in various regions throughout the world such as North America, parts of South America, Europe, the Middle East, Central Asia, and Australasia. The HP service is reference-station-dependent, meaning that the performance degrades as the user moves farther away from the nearest reference station (with a 300-mile limit).

Fugro/OmniSTAR’s other precise service, XP, is based on data licensed from JPL. The XP service offers horizontal accuracy of +/-15cm. The HP and XP services are similar in accuracy, but the JPL-based XP service offers global service rather than a regional service like HP. The difference is that while the HP service is baseline-dependent, the JPL-based XP service is not. That enhances Fugro/OmniSTAR’s coverage in remote locations where reference station coverage is sparse.

NavCom Technology

A leading-edge GPS design company licensing data from JPL is NavCom Technology, Inc., from Torrance, CA. Although the company name isn’t well known in the Survey/Construction industry, many of the engineers at NavCom are the same ones that designed the original Leica survey receivers while they were at Magnavox. There is some pretty high-end GPS design talent there — enough that John Deere Company bought NavCom, which now operates as a wholly owned subsidiary of Deere.

NavCom created and operates a GSBAS (Global Satellite-Based Augmentation System) called StarFire. While NavCom operates its own network of 20 worldwide GPS reference stations, it also has license agreements with JPL for reference station data and certain software. NavCom then refines and optimizes the data for NavCom receivers and distribution via the StarFire network. The result is that StarFire can deliver horizontal accuracies in the sub-10cm range after initialization.

NavCom has also created an interesting innovation it calls RTKExtend. Users of traditional RTK systems know that when the data link is interrupted, RTK operations are halted until the data link can be re-established. However, NavCom has combined traditional RTK with its StarFire network to assist RTK users. Users begin work using the traditional base/rover RTK configuration. If the data link is interrupted, the NavCom receiver automatically transitions to use the StarFire network, so the user can continue to operate at the centimeter level for up to 15 minutes.

Satloc, Fugro/OmniSTAR, and NavCom are just a few examples of commercial organizations that have successfully utilized JPL’s leading-edge GPS technology. There are also applications outside of the high-precision industry, such as mobile phone service providers licensing JPL to provide A-GPS data for E-911 anywhere in the world. With its unique global reach, JPL’s technology enables precision GPS applications even in regions of the world that lack infrastructure. It’s truly impressive to realize that decimeter-level positioning is available in most places in the world today; it’s just a matter of how to deliver the corrections. With the proliferation of wireless communications, even this problem will eventually be solved.

DOT Throws NDGPS a Life Preserver

It appears the US Department of Transportation has bought the Nationwide Differential GPS system (NDGPS) another year. The FY09 Presidential Budget Request was released earlier this week, and it contains a line item in the Research and Innovative Technology Administration (RITA) budget for NDGPS in the amount of $4.6M for operations and maintenance of the current system until October 2009. There is no budget item for the planned build-out of NDGPS. The budget request is subject to approval by Congress, but most likely this will go through.

The funding request is neither a thumbs-up nor a thumbs-down for NDGPS. The FY09 $4.6M budget request for NDGPS merely means that the DOT hasn’t figured out what to do with NDGPS yet, and the pain of having to fund a decommissioning program outweighs the $4.6M to keep it running for another year.

I think it’s the right decision. That may be intriguing to some of you who have followed my criticisms, but they have principally been directed at the stewards of NDGPS, not the program itself. RITA, regardless of how incompetent it has been at trying to understand this, needs more time to have a chance of comprehending how NDGPS is used.

Last year, RITA was funded $400,000 for a “needs assessment” of NDGPS. In other words, the administration is supposed to study and understand who is using NDGPS. Their primary attempt at this was opening a formal docket for accepting public comment last fall. You can read the Federal Register Notice here.

With an initial deadline for public response of October 1, 2007, the responses were very weak; about 30 comments were collected. The deadline was ignored by DOT, and more comments have been trickling in, with the last one posted January 28, 2008. As of February 4, 2008, there were 124 comments. However, because the explanation in the docket was written so poorly, some of the comments are not about NDGPS and obvious confusion exists between NDGPS, CORS, and OPUS. I read through every comment submitted.

After culling out the statements from by people who didn’t understand NDGPS or made meaningless comments, nearly one-third of the responses in favor of NDGPS were from National Park Service employees. Several submissions represented federal and state government users, from agencies such as the USDA, state DNRs, state DOTs, state geodetic surveys, and county and local governments. It’s hard to assign a number of users to those sorts of submissions, though. For example, in the USDA comment, it claims to have 7,000 GPS receivers in use nationwide, but you and I know that only a very small percentage use the NDGPS stations being considered for decommissioning. The USDA commenter also wrote that the loss of CORS “would have a severe impact on high-accuracy positioning.” Well, that’s not the case, so discounts the credibility of the agency’s support.

It’s sad that a pioneering GPS program such as NDGPS is being treated as it is today. Whether you support NDGPS or not, it has earned a fair shot — and it’s not getting it. That’s why I agree with the decision to fund it for another year while RITA pulls itself together. It will be very interesting to read the results of RITA’s $400,000 “needs assessment” report that was due to be completed January 30, 2008. If it’s anything like the joke of a report entitled “NDGPS Study” that was presented last fall at the CGSIC meeting in Ft. Worth, just go ahead and shoot me now.

Since the RITA docket failed to communicate to the public just what effect the loss of 26 NDGPS site would have for both NDGPS users and CORS/OPUS users, I’ll attempt to spell it out here, as clearly and concisely as possible.

What’s at Stake?

If the 26 NDGPS sites cease to operate, you will not be able to receive DGPS corrections from these sites.

Map of current DGPS and NDGPS sites:

Map of DGPS system minus the 26 NDGPS sites:

Following is a list of the 26 NDGPS sites on the chopping block:

• Hackleburg, AL (HAC)
• Flagstaff, AZ (FST)
• Bakersfield, CA (BKR)
• Chico, CA (CHO)
• Essex (Fenner), CA (CAE)
• Pueblo, CO (PUB)
• Macon, GA (MCN)
• Hagerstown, MD (HAG)
• Pine River, MN (PNR)
• Billings, MT (BIL)
• Polson, MT (PLS)
• Greensboro, NC (NCG)
• Medora, ND (MDR)
• Whitney, NE (WHN)
• Albuquerque, NM (ABQ)
• Austin, NV (AST)
• Hudson Falls, NY (HDF)
• Klamath Falls, OR (ORK)
• Seneca, OR (ORS)
• Hawk Run, PA (HRN)
• Clark, SD (CLK)
• Dandridge, TN (TND)
• Hartsville, TN (HTV)
• Summerfield, TX (SUM)
• Myton, UT (MYT)
• Spokane, WA (SPN)

What Alternatives Exist?

If you depend on one of the above sites for DGPS corrections (not CORS or OPUS but beacon corrections), what are your alternatives if the site is shut down?

1. The easiest choice is to switch to WAAS as a correction source. Most receivers are WAAS-enabled and, like NDGPS, it’s free. However, you’ll need to reconcile the horizontal datum difference between the two. NDGPS uses NAD 83(CORS96) and WAAS uses WGS-84(G1150). I’ve done this many times; it’s not difficult, but it needs to be done or you will introduce 1+ meter error.

Caveat emptor. Some GPS receivers handle WAAS better than others. Check for firmware updates from the manufacturer of your equipment. Also, some receivers don’t handle WAAS well when you are working under tree canopy or around buildings.

2. If you don’t require real-time corrections when you’re in the field, then you can choose to post-process your data. Post-processing software is fairly automated these days, but inconvenient nonetheless.

3. If you absolutely need submeter positioning in real time and your receiver isn’t capable of providing that via WAAS, there are several options.

OmniSTAR is a commercial provider of submeter and decimeter corrections. It may or may not work where you work, however, because it’s got a line-of-sight limitation. If you’ve got a GPS receiver with an OmniSTAR receiver already built in (e.g., Trimble ProXRS), then it would be relatively painless for you to try it. I seem to recall that OmniSTAR has a trial program of sorts.

RTK networks are popping up all over the country. Some are able to provide submeter corrections to mapping receivers via a mobile phone. Mobile phone data plans are relatively inexpensive, and you may even be able to rent one from a local GPS dealer when you need it. Most RTK networks charge a subscription or membership fee, but it doesn’t hurt to ask how they could accommodate you.

Believe it or not, it’s not that hard to take control by setting up your own portable base station and broadcast corrections. Yes, you need two GPS receivers (one to generate the corrections), and you need a way to get data from one receiver to the other (UHF radios, spread-spectrum radios, NTRIP, etc.), but it’s doable. It’s a little painful to put the system together, but once you’ve done it, you’re set for life. You don’t rely on anyone else.

Effects on CORS/OPUS Users

In shutting down the 26 NDGPS sites, one piece of collateral damage would be the loss of CORS and OPUS for post-processing using those sites. Is it an issue? For CORS and OPUS users, it’s not; for OPUS-RS users, it might be. I’ll explain.

First, let’s get definitions out of the way. When I write CORS, I’m referring to accessing RINEX data for L1 C/A post-processing. That’s you folks who use a Trimble Pathfinder, ProXR, etc., and post-processing the data to obtain meter-level accuracy. When I write OPUS and OPUS-RS, I’m referring to the National Geodetic Survey’s Online Positioning User Service, whereby you submit L1/L2 data and have their OPUS post-processing software reduce your data to centimeter-level accuracy and return corrected coordinates to you.

For CORS users, the loss of your favorite NDGPS site won’t affect you, except that you’ll have to use either the next-closest CORS site or a regional reference station from the US Forest Service or state/local government. There are a ton of them around, so that shouldn’t be a problem.

For OPUS users, the loss of the NDGPS sites won’t affect you. OPUS provides good results when using sites that are 500, 600, and even 700 kilometers away. If you go to http://www.ngs.noaa.gov/OPUS and click on Recent Solutions, you’ll see solutions from as far away as South America. I interviewed Dr. Dru Smith from the National Geodetic Survey in September 2006, and even back then, he said the days of needing to “use your favorite CORS” station are over. The OPUS software, he said, is designed such that an increased baseline distance is not an issue to be concerned with given the high density of CORS stations.

For OPUS-RS users in certain areas, the loss of the NDGPS sites may affect you. The difference between OPUS and OPUS-RS, to the user, is that OPUS occupations require a minimum of two hours, whereas OPUS-RS only requires a minimum of 15 minutes of occupation time. But a limitation of OPUS-RS is that the user position must be within 250 kilometers of three CORS; those three CORS stations must surround the user position (think good geometry). In certain regions, that will create a problem for users.

NGS has already conducted preliminary studies, determining that CORS coverage for OPUS-RS users in some regions of the country is deficient even with the NDGPS sites still active. Northern Maine, northern Minnesota, North and South Dakota, Iowa, Nebraska, Montana, Wyoming, Idaho, and northeastern Washington have been identified as deficient regions for OPUS-RS users, according to Dr. Richard Snay of NGS. Decommissioning the NDGPS sites in those areas would magnify the problem. On a positive note, Snay did say that NGS will soon be adding several CORS from the Minnesota Department of Transportation, so that will help OPUS-RS users in the region.

What’s the solution for the OPUS-RS users who would be affected if the DOT decommissions the 26 NDGPS sites? The easiest, and only, solution I’d recommend is to revert back to using the original OPUS program. This means planning for two-hour occupation times instead of 15 minutes. Secondly, I’d start lobbying your state DOT, county, and whoever else might be interested in setting up a cooperative CORS site in your area.

In summary, the impact of shutting down the 26 NDGPS sites has a minimal impact on CORS/OPUS/OPUS-RS users.

Back to the Budget

The FY09 NDGPS funding request is still only good enough to stop the bleeding for another year; it doesn’t solve the problem. When its study is completed, I seriously doubt RITA is going to find enough transportation applications to justify continuing to fund NDGPS under the DOT umbrella. Realistically, it’s going to be up to federal and state government users in the affected regions to pony up the funding. You can bet that no private entities are going to contribute significant funds, if any at all. They’ll find another solution before going down that road

Listed below are some of the major government supporters (or associations who represent government agencies) that submitted public comments in support of NDGPS. I think it will be up to them, and others, to come up with at least the Operations/Maintenance budget of approximately $5 million annually to sustain (not build out) the NDGPS as it is today.

• USDA (including US Forest Service)
• National Park Service
• Farm Service Agency
• Bureau of Land Management
• Maryland DNR
• Iowa DOT
• South Dakota Association of Local Government
• California DOT (CALTRANS)
• State of South Dakota
• Association of American Railroads
• North Dakota DOT
• North Carolina Geodetic Survey
• North Dakota Water Commission
• Washington DOT
• Idaho DOT
• National Association of State Departments of Agriculture
• Virginia DOT

3D Machine Control

One of the hotter topics in the construction industry these days is GPS/GNSS. If any of you attend the World of Concrete exhibition in Las Vegas, you’ll see many examples of how GNSS is being implemented in construction environments. The exhibition is expected to attract more than 1,700 exhibitors and 90,000 attendees this month. I’m sorry I’ll miss it this year, but if you do attend, you’ll find the usual GNSS (and related) suspects exhibiting: Topcon, various Trimble divisions, Leica, Sokkia, Seco Mfg, CST/Berger, Berntsen, etc.

Although the U.S. real estate construction market is clearly slowing (or shall I say dying?), the commercial construction market seems to be holding its own for the time being. The demand for construction automation equipment is still there, but I hear more about construction (and surveying) outfits wanting to rent GNSS equipment as opposed to buying it. This makes sense, as confidence in the economy is clearly waning.

Regardless of construction industry trends, there’s no lack of equipment automation opportunities (GNSS-wise) in the construction industry. Of course, precise positioning (topo surveys, construction staking, grade checking, establishing control, etc.) is one area of opportunity, but there’s also not-so-precise positioning, like navigating to job sites (a la “In 500 feet, turn left on Main Street”) and asset tracking (“Yes, Mr. Job Superintendent, we delivered that 2,500 feet of 2-inch PVC this morning at 9:10am; would you like to know exactly which staging area we delivered it to?”).

But perhaps no GNSS automation is causing such a stir as 3D machine control. Actually, it’s not 3D machine control itself, but the matter of who is technically and legally is able to provide the site data that’s used by the 3D machine control equipment.

I think the issue can be summed up in three statements:

1. Construction firms need 3D site data in order to use their 3D machine control equipment.

2. Engineering firms, those responsible for generating the plans, are hesitant to give up/generate the 3D site data because they’re concerned about exposure (errors and omissions).

3. Surveying firms, specifically those specializing in construction staking, aren’t too hot about the 3D machine control concept because it significantly reduces the need for construction staking.

I don’t think anyone knows how this is going to shake out yet, but I believe one thing is certain. The value proposition of 3D machine control for construction firms, when used on the right type of projects, is just too great for it to be ignored. As the old saying goes, just follow the money. As long as you believe that, then the responsibility of the 3D data preparation really doesn’t matter, because it’s going to happen. Granted, there might be a catfight before it’s all through, but it will be resolved.

I’ve sat through a couple of friendly discussions on this subject, must recently at the Trimble Dimensions conference, where folks — construction firms, engineers, and surveyors — had a chance to voice their opinions. I’ve also had the opportunity to work with a number of each of them. One recurring theme that stands out in my mind is the efficiency and resolve of construction companies. Well, maybe not efficiency at times, but certainly the resolve. They understand, as much as anyone, that time is money.

That’s a major reason they are so gung-ho on 3D machine control. The idea of not having to wait around for someone to pound or re-stake grade stakes or construction limits or whatever is like RTK: it’s addictive. In fact, contrary to what some may say, construction superintendents and operators are quite resourceful.

“Joe Engineering Co. said they weren’t going to provide the 3D site data?” Well in that case, Mr. Job Superintendent might just turn around and digitize the 100-foot-scale paper plans they’ve got. Two days later, they load up the 3D site data, and they are off and running.

I know, I know. That raises all kinds of issues. Copyright infringement, liability, etc. By the time you’re done listing the issues and debating them, the construction company has finished the project and moved on to the next job. Is that right — or even legal? Maybe, or maybe not, but that’s reality, at least for now.

The Solution?

To quote Chris Matthews from his book I just read, entitled Life’s A Campaign, “The people who show up get the chances.” I think it’s a mistake for engineers/surveyors to stonewall construction firms and attempt to withhold 3D site data. I think they’ve got to stay in the game and keep the data flowing.

Is it business as usual and just pass the DWG, Ma’am? No, of course not. There’s even an opportunity for generating revenue. Contractors are going to pay for 3D site data that has been certified for 3D machine control, if their other choices are using a dated, non-certified DWG file that’s passed through ten different e-mail threads, or trying to digitize paper site plans.

The game is changing. Are you going to show up?

GPS

On the GPS front, I’m going to paraphrase, plagiarize, and otherwise copy from my fellow newsletter editor Don Jewell, who writes the Military & Government PNT newsletter. He spent decades on the inside looking out (think Lt. Col. Jewell) and offers interesting perspectives.

First off, after a relatively quiet period since launching the first new modernized satellite, the Block IIR-M (offering the new L2C signal), in September 2005, there has been a flurry of activity and announced activity in the past 13 months.

First — Sept. 25, 2005. PRN 25/SVN 53 . Slot C4.
Second — Sept. 26, 2006. PRN 31/SVN 52. Slot A2.
Third — Nov. 19, 2006. PRN 12/SVN 58. Slot B4.
Fourth — Oct. 17, 2007. PRN 15/SVN 55. Slot F2.
Fifth — Dec. 20, 2007. PRN /SVN 37. Slot C1.

Remember, a total of eight IIR-M satellites were built; the GPS Wing says the remaining three will be launched in 2008. One of the remaining Block IIR-M satellites has been modified by Lockheed Martin, with the capability of broadcasting an L5 non-operational test signal. The L5 operational signal is planned for the next-generation GPS satellite, the Block II-F. The first II-F was due to launch in 2008, but this doesn’t seem likely…and it seems less urgent since the IIR-M modified to broadcast an L5 test signal will secure the signal spectrum. Securing a signal frequency, especially with the competing satellite systems from other countries is not a simple task — but we’ll save that discussion for another time.

So, from all public sources of information available, the current IIR-M launch schedule looks something like this:

Sixth — Mar. 13, 2008.
Seventh — June 2008.
Eighth — October 2008.

This is the flurry of activity I was referring to. Essentially, five launches within a twelve-month period.

And this is where I bring in some of Don’s valuable info:
“In the current constellation there are indeed 32 satellites, and normally that would be nearly the perfect constellation configuration, but a few of the older satellites and payloads are ‘single string’ in space parlance or on their last legs and require substantial care and feeding, including power management, by the very talented personnel/crews at the 50SW (Space Wing), 2SOPS (Space Operations Squadron) at Schriever AFB in Colorado, and the intrepid engineers at the GPS Wing at Los Angeles Air Force Base in California.

“Each GPS satellite is designed with an ‘A’ and a ‘B’ side that approaches 100% redundancy for critical systems. Several of the satellites were switched to the ‘B’ side years ago and have significantly outlived their design life, which differs with each series of satellites launched.

“Therefore, don’t be surprised that as we launch more and more GPS satellites (IIRM+s), the number of active satellites in the constellation stays the same. Since we have 32 satellites on orbit, remember that is almost the optimum number, we are in a replenishment mode, and attempting to maintain the constellation at the optimum number while still adding new capabilities, or modernization; a good thing for war fighters when we are involved in several hot conflicts/wars around the globe.

“Now, what about the nine possible failures of the IIA series GPS satellites? The satellites in question are all at or beyond their design life and have critical failures; they are being kept alive by heroic means that require exceptional amounts of time and money. If the worst should happen and all nine IIA birds fail, then we would be down to 23 satellites which is far from the optimum number — but remember we will be launching the rest of the IIRM satellites at the same time and that should put the number of on-orbit GPS satellites at about 29. Colonel Dave Madden says the goal is to stay as near the optimum number as possible but to certainly never go below 27 satellites if possible.”

So, I think the conclusion to be drawn here is that those of you who are experiencing “PDOP spikes” during the day that prevent you from being productive when using RTK will continue to experience those, even with the new GPS satellite launches. I mention RTK because that is the technology that relies most heavily on having a consistent number of observables (6+). Static post-processing users are affected, but to a lesser extent.

The bottom line, and I’ve made this point many times in the past, is that if you want more satellites observable, the solution in GLONASS. That subject transitions nicely into my next discussion.

GLONASS

Why is it that we always seem to hear about GLONASS satellite launches, but the number of operational GLONASS satellites never seems to increase significantly (and even decreases)? The answer is that legacy GLONASS satellites had a poor operating life span — well under four years. The good news is that the new GLONASS-M satellites they’ve been launching have a “guaranteed” operating life of seven years.

Since I touched on this subject last fall, six more GLONASS-M satellites have been launched: three on October 26, 2007, and another three on December 25, 2007 (Russia’s Christmas gift to GNSS users). Two of the October 26 satellites are operational, so there are four left in orbit and pending operational status. There are twelve operational GLONASS satellites as of December 29, 2007. This could increase to sixteen in the next couple of months as the four satellites already in orbit are made operational. That would be, by far, the most operational GLONASS satellites we’ve seen in recent years.

This is great news for GPS/GLONASS users. Actually, GPS/GLONASS users gain more marginal benefit from GLONASS satellites than from GPS satellites because GLONASS satellites are on different orbital planes than GPS, and therefore, offer a better opportunity to increase the quality of the satellite geometry (e.g., decrease your PDOP).

As in 2007, six GLONASS satellites are scheduled to launch in 2008. This is good, but we’ll probably see some legacy GLONASS satellites fail also. There are two that are past their fourth birthday, and three that just turned three years old last month. In the best-case scenario, we could see 22 operational GLONASS satellites a year from now. In the worst-case scenario, I can’t imagine having less than 14 or so available to us. Not bad considering we had as few as nine available during certain times in 2007.

Although it’s been a rough ride at times, I continue to be a passenger on the GLONASS bandwagon. You can keep up with the GLONASS constellation status by visiting

this Russian Space Agency website.

Topcon/Sokkia Merger

 

Switching gears a bit, we move on to December 10, 2007, when the Japanese Fair Trade Commission (JFTC) approved the Topcon/Sokkia merger. JFTC approval was needed because both companies are headquartered in Japan. The only constraint is that “non motor-driven total stations” sold in the Japanese market must be sold through a third party “in order to clear antitrust concerns posed by the JFTC,” according to the Topcon press release. You can view the entire press release here.

I think this is a boon for both Topcon and Sokkia. It gives Topcon another distribution channel to push its GNSS technology. It gives Sokkia access to a broader range of GNSS technology than they have with Point, Inc., their joint venture with NovAtel. Also, Leica recently bought NovAtel. Since Leica is a direct Sokkia competitor, it put Sokkia in a difficult position if the Topcon merger didn’t go through.

I don’t think this particular merger is a bad thing for the user community. My guess is that you’ll see some dual branding, like you did when Trimble acquired Spectra Precision. Even though it’s all Trimble technology, it markets the EPOCH GPS system under the Spectra name for the budget-minded user while still maintaining higher selling prices for its technology under the Trimble brand name. I could be wrong, but I bet Topcon/Sokkia does something like this.

ION GNSS 2007 Report

I hope some of you had a chance to read my ION GNSS conference blog, as well as those of my fellow editors who attended the conference. I think Editor-in-Chief Alan Cameron’s brainstorm about this was very good, and I expect we will repeat next year. If you missed it, you can still view it on the GPS World Web site. It’s worth a few minutes of reading to get the flavor of what the hot issues were.

For this newsletter, I’m going to hit the highlights and comment on them, so fasten your seatbelt.

CGSIC  Meeting

Every year, the CGSIC (Civil GPS Service Interface Committee) holds two days of meetings before the ION GNSS conference; this year was no different. There were status briefings on the different programs, such as GPS and GPS modernization, GLONASS, Galileo, Compass, QZSS, WAAS/EGNOS, NDGPS and other activities. The CGSIC provides PDFs of the presentation on its site.

Satellite launch schedule. The GPS Wing plans to launch the rest of the IIR-Ms in FY08. One was launched last week, on October 17. Its designation will be PRN 15/SVN 55 when it’s declared operational in early November.

The next launch is scheduled for December. Then March 2008. Then June 2008. The launch schedule for the last one hasn’t been announced yet.

However, the GPS Wing said that they plan to launch the first Block IIF satellite (with L5 in addition to L2C) before they launch the last IIR-M. This will be interesting, because rumor has it that the Block IIF is waaaay behind schedule and has almost no chance of being ready in 2008.

Another interesting twist is that Lockheed was awarded a contract last Spring to enable a IIR-M satellite to broadcast an L5 test signal. Something about protecting the L5 frequency with the ITU (United Nations International Telecommunication Union) until the first IIF is ready.

GLONASS. For you GLONASS users (or potential ones), the future is brightening somewhat. I’ve been touting GLONASS for some time, and the reliability of operational satellites has been disappointing. One could say that this is due to the legacy satellites, which are averaging well under four years of operational life, but that isn’t the whole story. While the newer GLONASS-M satellites supposedly have a seven-year life guarantee, the track record for the GLONASS-M really isn’t that great. For example, of the three GLONASS-M satellites that were launched in December 2006, only one is operational today.

There are seventeen GLONASS satellites in orbit. Only eleven are operational. Seven are the newer GLONASS-M models and four are the legacy models.

The bright spot is that six more GLONASS-M satellites are scheduled to launch by the end of this year—three this month and three more in December. The number of usable GLONASS satellites really needs to improve. GLONASS can’t seem to get above 13 operational satellites, and many times it’s been down to 9. Don’t count on the six new satellites to be operational in the near future. Sometimes, it takes more than six months after launch for them to be declared operational. I wish it wasn’t the case, but that’s a fact. Sometimes, I beat up on the GPS Wing for their slow pace, but after they launch one, it’s operational within thirty days—and it’s reliable.

The GLONASS folks also announced that they are migrating the datum used by GLONASS, named PZ-90, to the ITRF (International Terrestrial Reference Frame). The revised GLONASS datum is named PZ-90.02. It was implemented on September 20, 2007.

It doesn’t match ITRF05 exactly, but I understand their intent is to do so eventually. They publish the PZ-90.02 difference from ITRF05 as:

Delta X: -36cm
Delta Y: +8cm
Delta Z: +18cm
There is no rotation.

Lastly, the long-awaited news about GLONASS possibly migrating to CDMA (to be compatible with GPS and Galileo specs) was discussed. The decision seems final (except the final government stamp) that GLONASS will eventually offer a CDMA signal interoperable with GPS L1 (called L1CR) and GPS L5 (called L5R). Not much else to mention on this now because it’s years—even a decade—away from now, but good news for users nonetheless.

Galileo. There’s a lot to write about this, but also nothing to write. As users, we would benefit tremendously from Galileo. But it’s time to quit talking and start doing. That’s not to say they haven’t been doing; hundreds of millions of dollars are being spent developing Galileo, but the same discussions about the benefits are becoming stale.

The biggest, and possibly best, news is that the European Union is not considering the PPP (Private-Public Partnership) funding model any longer. Looks like it will be a publicly financed system, at least into initial operation.

To borrow a slogan from Nike: Just Do It.

NDGPS. I blogged quite a bit about this during the conference.

Not much post-ION conference information on NDGPS. I see that the invitation for public comment on NDGPS is now closed. Last I checked, there were only about 42 public comments. I read through most of them; about 25 percent were not relevant. There were some very good comments in support of NDGPS.

NDGPS is probably going to survive in one form or another. I think it’s likely that some stations will stay and some will go away. If that’s the case and the USCG picks up the 12 they say they will, then the reduction in coverage will be minimal. The other possibility is that once the purse-string folks understand the cost of shutting down a site, that may be a big enough deterrent that the DOT finds the budget dollars somewhere to keep them going.

Satellite-Based Augmentation Systems (SBAS)

WAAS. Finally, long-term WAAS geo configuration is settled. The two legacy WAAS geos stopped broadcasting a couple of months ago. Right after the ION conference, the WAAS ground software was upgraded to incorporate the new reference stations in Canada and Mexico. WAAS users in Southern California, Southern Texas, Maine and Minnesota should see improved performance. The FAA GNSS program manager, Leo Eldridge, also stated that they are considering adding a third WAAS geo at 125W longitude, but that would be 3-4 years down the road.

EGNOS. The European Space Agency says EGNOS is in Initial Operations Phase (IOP) and expects it to enter Long-term Operations Phase (Safety-of-life, Commercial Services) in a couple of years. EGNOS is usable now and there are three broadcasting GEO satellites. See my July 2007 column for details.

The ESA reports that EGNOS coverage will expand northward, and eventually into Africa.

MSAS. MSAS was declared operational on September 27, 2007. There are two GEO satellites identified as PRN 129 and PRN 137; if your receiver doesn’t recognize them, check with the manufacturer for a firmware update. Ground users should be able to benefit from MSAS in a broad area including Australia. Here is a coverage map:

Industry Developments

Javad GNSS. Ever the GNSS maverick, Dr. Javad Ashjaee came to an agreement with Topcon, and now both companies are free to compete in all markets as of January 2008. Ashjaee has plenty of experience competing in survey/construction, so I would expect to see his company introducing products to that market next year.

Septentrio. It’s not often that you encounter a new designer of high-performance GNSS receivers. This little-known Belgian company might prove to be a factor in the GNSS market. They’ve positioned themselves as an OEM supplier, much like Novatel, so you probably won’t see their name on a product that you use, but they may make the guts of a product you use. They just opened a U.S. office in Los Angeles, California, that is run by the guy (Chris Litton) whose father (James Litton) founded NavCom Technology, a competitor of sorts. Weird.

NavCom Technology . NavCom is a wholly owned subsidiary of John Deere Company that has been focused on providing precision agriculture solutions for their owner. Now, that may be changing. They’ve hired two salespeople to develop external sales to achieve “NavCom’s revenue and growth goals for GPS products and services in direct sales, government customers, system integrators, and OEMs,” according to their press release.

Some of NavCom’s key engineers developed the first Leica survey receivers while at Magnavox, so they have the technical capability. But creating a better mousetrap in the survey/construction market isn’t necessarily the name of the game. They’ve got to have a solid dealer network, and that isn’t easy.

Leica/Novatel. No big surprise here: Leica (Hexagon) bought Novatel for $390M ($50/share). Novatel has been Leica’s sole source of GNSS technology for several years. If you bought Novatel stock five years ago for a couple of bucks a share, you did well. Also, the Topcon/Sokkia acquisition is still waiting for Japanese government approval, and with Novatel being Sokkia’s source of supply for GNSS technology, Sokkia is in a really weird position.

GNSS Update,  Version 2.0

I, along with John Flick, co-authored a fairly in-depth piece on GNSS in the April 2006 issue of Geospatial Solutions. The basics of that article are still applicable, but here’s an update on GNSS events that have transpired since then — with a bit of speculation and guesstimation thrown in.

The most talked about GPS modernization subject since then is L2C.

There are now three IIR-M satellites in orbit that are L2C-capable. Most GPS receiver manufacturers have introduced “L2C-capable” receivers. Although the GPS Wing reports that no data is currently broadcast on L2C, the pilot carrier for L2C is available and useful by L2C-capable receivers. In fact, some experts say that the data on L2C is less important than the carrier. The reason is that with the complexity of semicodeless (legacy) L1/L2 receivers, a real signal loss of 3dB on L2 results in a net loss of 6dB. Using the L2C carrier, it’s a 1:1 ratio.

You can read an older (2001), yet still valid article written for GPS World on L2C. Ignore the dates, because they aren?t valid any longer. Also, ignore references to consumer L2C receivers. The viability of those was effectively nixed when Galileo decided not to use that frequency.

Code on L2C will add some marginal benefit, but that won’t be available for a while still. The GPS ground infrastructure is aged and wasn’t designed to handle L2C codes. Some of the infrastructure dates back to the 1970s. Next month, the GPS control segment will undergo a major upgrade as part of the Architecture Evolution Plan (AEP).

Still, the limiting factor for L2C users is the lack of satellites.

AEP Upgrade

The upgrade is a major step. But the GPS Wing says they’ve been preparing for more than a year for the transition. Some observers have voiced a sort of “the sky is falling” doom that GPS may stop working when they attempt the upgrade. I don’t buy that. I’ll worry about many other things before I worry about that. As my wife told me last weekend while we were watching the Blue Angels (U.S. Navy fighter aircraft demonstration team), “I’m glad those guys are on our side.”

One other note on the AEP upgrade. The current GPS control segment infrastructure is only able to accommodate 32 satellites. Next month’s scheduled launch would bring the current constellation to 32. Given that there will be four remaining IIR-M satellites to be launched after next month’s launch, but no way to accommodate them other than removing serviceable satellites from the constellation, the time for increasing capabilities is officially here. This AEP upgrade will expand that number to 60 and render this a non-issue for decades to come.

You can read more about the AEP upgrade here

Satellite Launches

Right now, there are five remaining Block IIR-M satellites to be launched. The last one was launched in late 2006. The good news is that the GPS Wing has stated one of their top priorities is to launch the remaining five. The next one is scheduled to launch next month. According to an interview by GPS World Editor-in-Chief Alan Cameron with then GPS Wing Commander, Col. Wesley Ballenger, Jr. back in March 2007, the schedule looks like this:

September 2007
December 2007
March 2008
June 2008
September 2008

As in the past, the schedule could slide due to various reasons (resources and/or technical primarily), but all indicators seem to point that the September launch is a “go” — except that it has now reportedly moved slightly to the left, to October 17. Politically, this launch is an important one because, traditionally, it goes up prior to or during the Institute of Navigation (ION) GNSS conference where the GPS Wing makes the “successful launch” announcement — except that won’t quite happen this time around

For precision GPS users, does it really matter what the launch motivation is — as long as they keep doing it? I don’t think so. The bottom line is that more is better.

Interesting Twist

The GPS Wing has said their desire is to launch the first Block IIF satellite (L2C, L5) before all the IIR-Ms are launched. The reason is to be able to take time to flush out any bugs, especially in a new satellite model, that may occur.

I have no doubt they’ve thought it through and it’s a solid strategy. But it sure complicates the scheduling and really lowers the confidence level that the IIR-M launch schedule will stick. Here’s why:

The AEP upgrade mentioned above is required in order to control the Block IIFs. But, my understanding from the GPS Wing media conference call last week is that another software “update” (beyond next month’s AEP upgrade) is required to the control segment before the first Block IIF can be launched. According to the GPS Wing, that “update” will occur Spring/Summer 2008 and therefore push back the estimated IIF launch date of March-May 2008 to Summer-Fall 2008. One would think this would impact the IIR-M launch schedule.

Furthermore, the Block IIF program has had its share of technical issues. Boeing is scheduled to deliver the first Block IIF in mid-December 2007 but that’s many months too optimistic. Rumor has it that it could be well into 2008 before the Block IIF is delivered. Then with testing and integration, we could be well into 2009 before it takes flight. It’s not hard to doubt the IIR-M launch schedule as laid out above.

Testing L5 on IIR-M

In April 2007, Lockheed was awarded a $6 million contract to develop and demonstrate a payload that will temporarily transmit L5 (1176Mhz) from a Block IIR-M satellite. L5 was originally planned for Block IIF satellites and it’s not likely this will change. All indicators seem to agree that this will be a non-operational, temporary test on one IIR-M to test L5 before Block IIFs are launched.

Not a lot of info on this, but I expect a new press release shortly.

More is Better

As high-precision GPS users, we’re on the leading edge of GPS technology. We push the technology hard and therefore we feel the bumps in the road before anyone else. The biggest bump now is the lack of satellite observables. I can’t count the number of people who have emailed me about the “down-time” during the day due to the lack of GPS observables — even in the wide-open plains of mid-western America, not to mention the beautiful, foliage-laden, topographically-broken northeastern US.

The bandaid for high-precision GPS users, to this point, has been to rely on the Russian system (GLONASS). Whereas three years ago, there were many high-precision, GPS-only receivers on the market, now they are the minority. Almost every high-precision GPS manufacturer offers a GPS/GLONASS receiver. But adding GLONASS to the mix isn’t enough. I’ve used GPS/GLONASS receivers. Sometimes GLONASS helps, sometimes it doesn’t. There aren’t enough GLONASS satellites to help all the time. But I generally advise high-precision users to spring the extra $$ for the GLONASS option because there’s not another choice if you want to add observables.

There’s not enough space here to update you on GLONASS, Galileo, and other GPS modernization initiatives so look for those in the coming months. Also, the ION GNSS conference is next month and I’ll be sure to give you an update on what I hear. There should be some good stuff coming from that conference.

NAVCEN and the CGSIC

I thought this would be a timely subject, since I’m heading off for two days of CGSIC/NAVCEN presentations before the ION GNSS 2007 conference starts on September 25. I’ll also be staying for the conference, and reporting back to you on what I hear there.

NAVCEN is an acronym for the U.S. Coast Guard Navigation Center. Its mission, according to its website, is to “provide cutting edge services for safe, secure, and efficient maritime transportation.”

CGSIC (est. 1987) is an acronym for the Civil GPS Service Interface Committee. It is the forum for the civil GPS community to communicate with GPS authorities, and vice versa. According to the CGSIC website, the committee “was established and chartered to identify civil GPS user needs in support of the Department of Transportation’s program to exchange information concerning GPS with the civil user community as part of the GPS ‘outreach’ program.”

The NAVCEN and CGSIC work hand in hand in facilitating communications for the civil GPS community; NAVCEN coordinates and manages the CGSIC. The NAVCEN site is one that you should have bookmarked in your web browser; there’s a lot of good information there. Here are some examples:

1. Notice Advisory to NAVSTAR Users (NANU) report: you can sign up for a daily e-mail that reports on the day-to-day status of the GPS constellation, or you can view the GPS constellation online. This is very helpful way to keep track of satellite outages that may affect your GPS field operations. For example, if a particular set of satellites is important to keep the PDOP low in your area, this is a good tool to let you know if one of those satellites is having a problem.

2. GPS Status Message (TIS-PF-NISWS) — This is daily GPS status report. If you subscribe to this mailing list, you will be sent an e-mail within 60 minutes of notification by the U.S. Air Force of a change to the constellation.

3. View and download the daily GPS almanac. (Both YUMA and SEM almanac formats — which most GPS mission planning software packages can handle — are available.)

4. View a list of DGPS and NDGPS sites broadcasting corrections. If you’re not sure you will be in range of a DGPS or NDGPS broadcasting station, this site provides details on each broadcasting station, including the precise location of the station, signal strength, expected coverage area and transmitting frequency.

The CGSIC coordinates some very informative meetings with very good information. Its membership is made up of U.S. and international private, government and industry user groups. The committee membership is free and open to anyone who is interested.

CGSIC meets at least once per year in conjunction with ION GNSS, which is usually held in September. However, there are subcommittee meetings throughout the year. There are four subcommittees:

• International Information Subcommittee.
• U.S. States and Local Government Subcommittee.
• Survey, Mapping and Geosciences Subcommittee.
• Timing Subcommittee.

The International Information Subcommittee last met in May 2007 in Geneva, Switzerland. Members are free to attend, but if you can’t, then you can download all of the presentations for a quick update. Going back and viewing previous years’ agendas and presentations is very informative.

The U.S. States and Localities Subcommittee last met in June 2007 in Bend, Oregon. I attended this meeting. There was good discussion on NDGPS, NGS initiatives and Network RTK. The Subcommittee also met in June 2007 in Minnesota. Notice the central theme of both meetings: NDGPS (but that’s another story).

The Survey, Mapping and Geosciences Subcommittee is a relatively new one. Not sure when they’ve last met, but I’ll get up to speed on that one at the CGSIC meeting. As for the Timing Subcommittee, I don’t stay current with that because it’s outside of the survey/mapping market.

Next week’s annual ION GNSS CGSIC meeting looks to be a good one: two days packed with all that a GPS connoisseur like me can handle. Day One is high-level information — policy stuff as well as program status reports on GPS, L1C, WAAS/LAAS and NDGPS.

Day Two is tough for me, because there are concurrent sessions by the three Subcommittees I follow:

• GLONASS, Galileo, EGNOS, QZSS/MSAS, GBAS/GRAS, Beidou/Compass from the International Subcommittee.
• HA-NDGPS, NDGPS and USCG DGPS from the U.S. States Subcommittee.
• CORS/OPUS, various NGS initiatives, RTK Networks and Space weather from the Surveying, Mapping and Geosciences Subcommittee.

You can find a detailed look next week’s CGSIC agenda here.

This year, GPS World is doing something a little different, and I think you’ll like it. My e-newsletter colleagues and I will be your eyes and ears during the CGSIC and ION GNSS meetings; “We’re Bringing ION to you!” is the theme. We’ll be writing daily reports on subjects we think may interest you, and the website will be updated twice daily during the week.

If there’s something in particular you want me to check out while at the conference, fire off an e-mail to [email protected], and I’ll do my best to cover it.