“There aren’t a lot of geodesists, but it’s good to have a few of us around,” says Thomas Meyer, a professor in the Department of Natural Resources and the Environment (NRE) and current president of the American Association for Geodetic Surveying.
Geodesy is a specialized field that uses mathematics and physics to measure the shape and size of the Earth, its gravitational field and its geophysical changes over time, such as plate tectonics, glacial melting and sea level rise. Meyer is engaged in a number of research projects that use geodetic technologies and methods to research animal behavior and improve map projections.
“Coordinate systems are the primary product of geodesy,” says Meyer. “Longitude and latitude don’t just exist – they have to be created. Geodesists are responsible for ensuring that the spatial coordinate systems people use to map and locate places or navigate are accurate.”
All maps are compiled from measurements that ultimately must produce spatial coordinates for the features being mapped, so all surveyors and mappers use spatial coordinate systems. Meyer teaches a land surveying course in which students learn how to use spirit levels and total stations for mapping areas roughly the size of the Storrs campus. During the course, students take measurements to compile maps that are used by UConn’s Facilities Operations.
“It’s one of the things we do that gives students something real to talk about and helps the University,” says Meyer. “We started doing the mapping about twenty years ago.”
The role of geodesists transformed when global navigation satellite systems, like the Global Positioning System (GPS), became widely used in the 1990s. This technology allows anyone with a GPS receiver to obtain relatively precise coordinates of their position from a constellation of satellites orbiting the Earth. Meyer notes that this information alone – the coordinates themselves — is not immediately helpful to most individuals unless it is tied to a geographic information system (GIS), a spatial technology that can overlay coordinates on a map or perform specific operations, such as finding the fastest route to a location. These advances allowed mappers to move beyond maintaining detailed maps of small areas to developing complex maps of a global scale that have a variety of uses across disciplines, including ecological research.
One of Meyer’s research projects is a collaboration with Panthera’s Puma Program in Wyoming. The initiative aims to use this information to understand the range of pumas and their behaviors with the goal of effectively and sustainably managing populations. Professors Vladimir Pozdnyakov and Jun Yan of UConn’s Department of Statistics are also partners in the research.
Meyer is helping ecologists determine the time pumas spend engaged in different activities: moving, resting or handling. Handling is the term used when pumas feed on a kill, which might occur over several days, separating the behavior from inactivity or other action, such as seeking new hunting grounds and more prey.
“Pumas spend so much of their time not walking in a directed manner that we felt, statistically, it was important to tease things apart,” says Meyer. “During handling, the puma will go out from the kill and come back then go out and come back again, over and over. That’s a very different kind of moving than changing hunting grounds.”
The pumas are tracked using GPS collars. To conserve battery life, the collars are programmed to determine a position at different intervals with hours possibly passing between receiving location data.
“The two points give us a probable maximum distance the puma went and we know there are some places that the puma could not go, like if there was a house,” says Meyer. “A puma can only move so fast, so we have some notion of the average velocity. Using this information, we can create a bounding shape, an ellipse, on a map with confidence intervals to help determine how much time the puma is spending moving, resting or handling.”
It is also possible to use these methods to track more than animals on the land. Meyer is studying the movement of salmon as part of another ongoing research collaboration. He is working with an environmental engineering firm and a former student on the project.
Salmon spawn in rivers. They travel downstream in their youth to spend most of their adult lives in the ocean before returning to their home waters to reproduce. Their ability to swim downstream and return upstream to propagate in natal rivers is made difficult by manmade structures, such as dams, that hinder their progress. The research helps measure the extent to which the salmon are using aides, like fish ladders, to make their journeys. This is helping managers determine the most effective ways to help salmon negotiate these obstacles.
Since it is impractical to track fish visually, the fish have acoustic tags implanted that allow researchers follow their movements. These transmitters send out a loud audio signal, a ping, that travels through the water and is registered by a listening device called a hydrophone. A network of hydrophones is placed throughout a body of water. Measuring the time it takes for the signal to reach these devices allows researchers to calculate the position of the fish. Using these data, Meyer is able to create maps of routes that fish swim.
“The mathematics involved is similar to tracking with GPS receivers. We were able to take those equations and tweak them a bit to solve problems with mapping movement underwater,” says Meyer.
The most recently published research of Meyer’s concerns refining map projections. All maps distort the shape of the Earth by representing its generally spherical shape on a two-dimensional planar surface. The larger the area then the greater the distortion of the map. Working with Craig Rollins of the National Geospatial-Intelligence Agency (NGA), Meyer is developing map projections that decrease the distortion for maps compiled at elevations far above or below sea level.
This research holds promise for being the foundation of the next generation of generally used coordinate systems,” says Meyer. “As I said, there’s not many of us, but the work we do is important.”