GPS World

Tag: Purdue University

  • Seen & Heard: Goodbye to QE2, saving Ukrainian heritage

    Seen & Heard: Goodbye to QE2, saving Ukrainian heritage

    “Seen & Heard” is a monthly feature of GPS World magazine, traveling the world to capture interesting and unusual news stories involving the GNSS/PNT industry.

    Photo:
    Screenshot: Lying in State Queue tracker

    Queue Tracker for the Queen

    After the passing of Queen Elizabeth II on Sept. 8, the British government launched a live queue tracker app to give people an idea how long they would have to wait to pay their respects at her lying in state at the Palace of Westminster. The app also used What3Words to help locate the end of the line using a three-word tag. The queue grew dramatically in the days before the funeral as tens of thousands lined up, some waiting as long as 16 hours. The app also showed locations of public toilets, drinking water and first-aid stations along the queue route.

    Lake Sarez. (Photo: Astronaut Photography Collection/NASA)
    Lake Sarez. (Photo: Astronaut Photography Collection/NASA)

    A Dam Problem Solved

    Lake Sarez, deep in the Pamir mountains of Tajikistan, was created only a century ago when a strong earthquake triggered a massive landslide. The area experiences considerable seismic activity, which could result in massive flooding downstream should a landslide dam break. With the help of 40 donkeys, 10 scientists and 30 staff from the National Time Service Center of the Chinese Academy of Sciences transported and installed a BeiDou-based deformation monitoring system at the dam. The team had to resolve technical problems in the rugged area, such as providing sufficient solar power and communications. With the system now operating, the dam is being monitored in real time down to the millimeter.

    Figure 3. (Image: CC BY 4.0, Remote Sensing 14, no. 17: 4274) Photo:
    Figure 3. (Image: CC BY 4.0, Remote Sensing 14, no. 17: 4274)

    Counting the Forest for the Trees

    Integration of aerial and ground-based mobile mapping sensors and systems is enabling a team of Purdue digital forestry researchers to locate, count and measure more than a thousand trees in a matter of hours. “The quick, accurate inventory of the global forest ecosystem will improve our ability to prevent forest fires, detect disease, perform accurate carbon counting and make informed forest management decisions,” said Songlin Fei, the Dean’s Remote Sensing Chair. The Purdue-made systems integrate GNSS and inertial navigation devices with lidar and cameras, deployed with manned aircraft, drones and backpack-mounted systems. The technology gathers a variety of information about each tree, including height, trunk diameter and branching formation. The team maintains the precise location and time tags of all acquired features.

    Photo: Skeiron
    Photo: Skeiron

    Saving Ukranian Heritage

    By the end of May, at least 367 incidences of destruction had occurred to Ukraine’s museums, churches, theaters and libraries. Through the project #SaveUkranianHeritage, mapping company Skeiron is capturing sites in high detail using laser scanning and photogrammetry. For a UNESCO-protected church in Lviv, the team gathered more than 300 individual laser scans and 6,000 photos to create a 3D model. The company has two laser scanners — a Leica C10 and Leica ScanStation P20, DLSR cameras and a drone. To support the project with funding or equipment, visit skeiron.com.ua/en/saveukrainianheritage/.

  • A drone can hear the shape of a room

    A drone can hear the shape of a room

    With a speaker and four microphones, drones can echolocate like bats

    Mathematicians at Purdue University in West Lafayette, Indiana, have found that drones can determine position with echolocation.

    The signal-processing research has potential applications for people, underwater vehicles and even cars, said Mireille “Mimi” Boutin, a Purdue University associate professor of mathematics and electrical and computer engineering.

    Boutin and Gregor Kemper, a professor of algorithmic algebra in the Department of Mathematics at the Technical University of Munich, have worked to reconstruct the wall configuration of rooms by using echoes picked up by microphones on the drone.

    Mathematicians found a method to hear the shape of a room using four microphones mounted on a drone. Pictured: Mireille Boutin. (Photo: Purdue University)
    Mathematicians found a method to hear the shape of a room using four microphones mounted on a drone. Pictured: Mireille Boutin. (Photo: Purdue University)

    When a microphone hears an echo, the time difference between the moment the sound was produced and the time it was heard is recorded. That time difference shows the distance traveled by the sound after bouncing on a wall — much like bats use echolocation to orient themselves with their surroundings.

    The challenge is to determine which distance corresponds to which wall, a process called echosorting. Sorting the echoes accurately ensures that all the walls heard are truly there. This way, the algorithm used does not produce “ghost” walls.

    The research is directly related to two complementary problems in engineering: localization (determining where you are in an environment) and mapping (determining the shape of your environment).

    The research, which uses methods from commutative algebra, proves that it’s possible for a minimal setup of four microphones arranged in a non-planar shape, along with a loudspeaker emitting a singal signal, to reconstruct a room.

    The microphones and loudspeaker could be mounted on a moving car, a robot navigating in an indoor environment, or an underwater vehicle exploring a wreck in the ocean. Some of these situations put restrictions on rotations and translations that can be applied to the microphone configuration. The impact of such restrictions on the reconstruction problem will also be studied in future work.

    The next steps will be to consider other scenarios, such as when the movement of the drone is restricted, or when the drone listens to the echoes of consecutive sounds as it is moving.

    Citation.     “A Drone Can Hear the Shape of a Room,” by Mireille Boutin and Gregor Kemper, SIAM Journal on Applied Algebra and Geometry, 4(1), 123–140, Published online Feb. 6, 2020, https://doi.org/10.1137/19M1248534.