Today’s blog post is brought to you by Dr. Didi Martinez.
One of the great things about living in an age of quick technological advances is that more and more scientific methods are accessible to those of us that do science every day! I am Dr. Adriana E. Martinez in general I research rivers using mapping and survey methods. One of the exciting tools I get to use in my work is drones. These days drones are pretty affordable and allow us to map out large areas in less than a day. I have used drones in my work on rivers locally as well as projects I have participated in all over the U.S. Recently, I conducted a drone flight at the Watershed Nature Center in Edwardsville with some students and colleagues from Southern Illinois University Edwardsville.
In order to map out an area we first have to get our geographic bearings. The first thing we do is set up a survey grade GPS.
This is a Topcon Survey Grade GPS which can calculate your latitude and longitude down to the accuracy of a few centimeters. This type of accuracy is imporant because we want the map we eventually make to be accurate. Otherwise, when we try to measure things on the map, the measurements won’t be accurate. In this photo Logan Pelo and Jesus Sanchez are setting up the GPS to communicate with the GPS satellites up in space. Next, we need to set out targets.
These targets are important because we will use the GPS to find the latitude and longitude of their exact center. When the drone flies overhead they’ll be captured in the drone photos and we can identify the latitude and longitude in them.
Once all the targets are set out in place we can now conduct the drone flight!
We set the drone to take a photo about every three seconds as it is flying over the entire area. For an area this size it takes about an hour and the drone has to land for a battery change about every 20 minutes. Once the flight is done we pack everything up, collect the targets and head to the lab!
In the lab and on a powerful computer we download all the photos from the drone as well as the GPS coordinates that were recorded on the GPS unit. The program Agisoft Metashape is then used to upload the photos and the coordinates. We go through each individual photo and identify the different targets. The program then stitches together all the photos and creates a 3-D point cloud.
The point cloud is a 3-D rendering and we can actually see topography on it and use it for different analyses. The program also creates a composite aerial photograph that pulls together all the individual drone photographs to create a map! In the map here you can see the GPS location of the targets too.
With this type of technology we can ask and answer all sorts of research questions about the areas we are mapping. For example, we could do multiple flights at different seasons or different years to look at change over time or differences in habitat characteristics. Using the topography map allows us to calculate area and volume. And being able to do a drone flight whenever we’d like allows us the flexibility to examine these any time we’d like without having to do a large aircraft (plane or helicopter) flight that would be much more expensive and time consuming. And its fun!
Photos taken by Howard Ash.
Maps created by Didi Martinez.