In my November 2023 GPS World newsletter, I highlighted the announcement made by the National Geodetic Survey (NGS) of the recipients of the NOAA FY 23 Geospatial Modeling Competition Awards. The grantees’ proposals include developing models to address what NGS denotes as the Intra-Frame Deformation Model (IFDM). The primary objectives of these projects are to modernize geodetic tools and models, as well as to develop a geodetic workforce for the future. A significant improvement in the new, modernized National Spatial Reference System (NSRS) is the time-dependent component being incorporated in the computation of reference epoch coordinates (RECs). That said, developing models that accurately capture the time-dependent component is extremely important to providing reliable, consistent, and accurate RECs. My February 2024 newsletter highlighted NGS’s grant to The Ohio State University for developing a fully kinematic reference frame for the Continental United States and Canada. Similar to the OSU project, a goal of the Scripps Institution of Oceanography (SIO) project is to provide an accurate IFDM, which will provide reliable, consistent and accurate RECs. On Jan. 10, 2024, Yehuda Bock, Ph.D., gave a presentation about this at the general membership meeting of the American Association for Geodetic Surveying (AAGS). His presentation can be downloaded from the AAGS’s website: https://aagsmo.org/.
Bock is director of the California Spatial Reference Center (CSRC), which is responsible for “establishing and maintaining an accurate state-of-the-art network of GPS control stations for a reliable spatial reference system in California.” I highlighted the CSRC in my June 2023 GPS World Newsletter.
Yehuda’s proposal included the following three activities:
- Create a formal Geodesy Program at SIO to address the nationwide deficiency of geodesists. Expand current geophysics curriculum – funding for five graduate students.
- Develop an IFDM to supplement the NSRS for users in regions with significant ground motions, using GNSS and InSAR/GNSS displacement fields (funded by NASA projects) and underlying geophysical models. CSRC will exercise the IFDM through its community of public, private and academic users of precise spatial referencing in our challenging region of secular and transient crustal movements.
- Investigate a unified vertical reference frame, including a marine geoid optimized to be consistent with the full spectrum of observations from modern gravimetric geoids (e.g., GRAV-D, ICGEM), remotely sensed observations (e.g., SWOT, ICESat-2), in situ ocean observations and assimilating ocean models and the TRF.
Yehuda’s project includes creating a formal geodesy program at SIO that will help to address the geodesy crisis. Anyone keeping up with my columns knows that I have been highlighting the geodesy crisis and programs that advance the science of geodesy (July 2020, November 2022, and December 2022).
Yehuda showed a slide that highlighted “What Geodesy Can Tell Us About Earth.” Looking at the slide, geodesists are needed in the field of climatology, meteorology, hydrology, geology, volcanology, oceanography, and glaciology, as well as surveying, mapping, and navigation. All these disciplines study Earth’s dynamic processes and involve geodesy.
The images “Geodesy Curriculum at SIO (PhD, MSc)”, “Geodesy Courses – 1” and “Geodesy Courses – 2” provide information about the Geodesy Program as SIO.
Notice that some of the courses focus on topics that are important to real world applications. For example, GNSS precise point positioning applications to seismotectonics, GNSS signal propagation applications to atmospheric remote sensing and GNSS reflection: soil moisture and sea level and the vertical datum.
In addition to the graduate-level courses, they are proposing an undergraduate course titled Geodesy and Geospatial Information. The purpose of the course is to provide students with the skills in geospatial systems that will provide opportunities for eventual employment in the public and private sectors.
Proposed Undergraduate Course
Title: Geodesy and Geospatial Information
Course justification and content objectives: Geodesy is the study of Earth’s size (geometry), shape (gravity field) and deformations (e.g., plate tectonic motions, subsidence). It provides access to a well-defined spatial reference system for precise geospatial information (latitude, longitude, height, elevation with respect to sea level) used for positioning, navigation, surveying and mapping. Geodesy is also an important discipline within the earth, atmospheric and oceanographic sciences, using observations of GPS and other satellite navigation constellations, remote sensing platforms (satellite and drone), and various terrestrial sensors. It is a data- and analysis-intensive discipline increasingly requiring modern data science methods. This introductory course will provide students with a solid background in geospatial systems for eventual employment in the public and private sectors. The course will also serve as a pipeline to the geodesy track at SIO/Earth Sciences and to other academic institutions and to alleviate the nationwide deficiency of geodesists. The objective is to provide basic knowledge of geodetic concepts for Earth and data scientists and the underlying geodetic framework for precise spatial information.
Learning objectives:
- Acquire basis concepts of geodetic science.
- Provide overview of geodetic instrumentation and observations.
- Develop elementary skills in geodetic data analysis.
- Explore existing geodetic infrastructure and data repositories.
- Experience hands on visualization and manipulation of geospatial information.
- Understand the underlying geodetic framework for precise spatial information systems.
- Provide example of data science applications in solving geodetic problems.
Preferred background: statistics, linear algebra, Matlab/Python
In my opinion, universities should provide a general elective course for undergraduate students that provides an introduction in how geodesy influences your daily routines. For example, how does my phone know where I am and how does it know the best route I should take to get to my destination?
The second task in the SIO proposal is to develop an IFDM. The concept of an IFDM is part of NGS’ modernized, NSRS. Several of my previous My July 2023 GPS World newsletter highlighted a presentation by Yehuda discussing a kinematic datum that uses an intra-frame velocity model to estimate positions at any time with respect to a reference frame and epoch.
As I mentioned in my July 2023 newsletter, California’s geodetic network is significantly affected by crustal movement. To help address this issue, the CSRS updated the NAD 83 coordinates, it is denoted as CSRS epoch 2017.5 (NAD 83). Part of the implementation of the CSRC epoch 2017.50 (NAD 83) was to have the new epoch-date coordinates transmitted with RTCM 3.0 data streams. This is something that other RTN operators from around the nation will have to do after NGS publishes the NSRS coordinates. The CSRS is a model from which others can learn.
During his presentation to AAGS, Yehuda highlighted his methodology of integrating InSAR and GNSS to develop an IFDM that provides for higher spatial resolution to improve the model between GNSS stations.
The boxes titled “SCIP Dynamic Datum Utility” and “Output from SCIP Utility” provide an example of an input and output of the utility, and the box titled InSAR/GNSS Integration for Higher Spatial Resolution” is a conceptual diagram of the concept.
Not only has this abbreviation been spelled out before, but here the full phrase appears three times, in three consecutive sentences.
(Image: AAGS website)
The image provides an example of the concept in the San Joaquin Valley, California.
The following statement is in the note section of the slide:
“Area of subsidence in San Joaquin Valley. Our weekly displacement time series at GNSS station P056 shows significant changes in subsidence rate over the period 2006 to 2022, for a total of 3.3 feet that reflects periods of drought and increased groundwater use. On the upper right is the InSAR time series at that location for a shorter period of time.” This shows the potential of using InSAR to improve the IFDM in areas of sparse CORS.
The third item in the proposal is to “Investigate a unified vertical reference frame, including a marine geoid optimized to be consistent with the full spectrum of observations from modern gravimetric geoids (e.g., GRAV-D, ICGEM), remotely-sensed observations (e.g., SWOT, ICESat-2), in situ ocean observations and assimilating ocean models, and the TRF.”
The images below provide a list of the reference surfaces involved in unifying the vertical reference frames and the observing systems involved in the project. Understanding the geoid at the land-sea interchange is important to estimating accurate GNSS-derived orthometric heights along the coast as well as in the oceans. My August 2021 newsletter highlighted the concept of establishing an International Height Reference System (IHRS) so that all countries could provide physical heights across their boundaries and over the oceans. This project would support that international activity.
This newsletter and my previous GPS World newsletter highlighted two of the grantees, \SIO and OSU, which included developing models to address what NGS denotes as the IFDM.
The SIO program includes creating a formal geodesy program at SIO that will help to address the geodesy crisis. In addition to the graduate level courses, they are proposing an undergraduate course that will provide students with the skills in geospatial systems that will provide opportunities for eventual employment in the public and private sectors. My next newsletter will address another NGS geospatial modeling grant awardee – Oregon State University’s proposal.
