Example of individual aerial images from 1948 before putting them together. I began by georeferencing the aerial imagery, which involved working with as many as 45 images per year.
I was assigned the task of image to image georeferencing the images and mosaicking them together using GIS programs so that I could compare how the landscapes changed over time. Images from USGS Earth Explorer (1953, 1974, & 1982) and USDA National Agriculture Imagery Program (2014). You can see differences in color and scale below: Examples of imagery from the Sandhills north of the Calamus River/Reservoir from 1953 (top left), 1974 (top right), 1982 (bottom left), and 2014 (bottom right). Each year was flown at a different elevation, had different coloration, and different resolution, which added to the already difficult job of comparing the images to one another. Georeferencing refers to the process of assigning images real-world coordinates in a GIS program. Images for more recent years (2012-2016) were accessible online, already georeferenced. We obtained imagery from May of 1948, June of 1953, August of 1974, and March of 1982. The Calamus River (before dam construction) is flowing from top left to bottom right. Images looked like this: Aerial image of the Sandhills from 1948. The oldest imagery was originally taken on glass slides and later scanned on a computer. The images were captured via airplane and photographed by sections. The process began by obtaining aerial imagery dating back to 1948. Orange dot shows the entrance to Calamus Outfitters at the Switzer Ranch north of the Calamus Reservoir in Loup County, northwest of Burwell, Nebraska. Study site (gray shading) in and around the Switzer Ranch. Black dots represent locations of time-lapse cameras, and the orange dot shows the entrance to Calamus Outfitters at the Switzer Ranch, the focal area of this mapping project. Location of the Sandhills (yellow outline) relative to the Platte Basin (blue shading). My task was to tell the story at a larger scale of the entire landscape across several decades. Already in place are the permanent PBT cameras that show us how these features change on a smaller scale at Latta Lake, Gracie Creek, and Shoemaker Lake these cameras have been capturing change since 2012. My project focused on the southeastern edge of the Nebraska Sandhills, west of Burwell, Nebraska, in and around the Switzer Ranch, an area of ongoing PBT activities. Mary Harner to tell the story of how water changes over time in the Sandhills of Nebraska through the use of historical aerial imagery and GIS programs. I have a background in Geographic Information Systems (GIS) and a strong interest in conservation. After that meeting, I knew I wanted to contribute to this project in some way.
I first learned about Platte Basin Timelapse (PBT) last spring and was thrilled to see how imagery was being used to convey important stories. I am currently a wildlife biology major at the University of Nebraska at Kearney, working on various undergraduate research projects.
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