So, I’ve been playing around with a tool that is now available on-line, showing elevation profiles, among other things, in the Red River Valley. In the flattest corner of the state, the difference in elevation across the basin is relatively low. Most elevation tools measure elevation contours at 5 or 10 foot intervals. LiDAR (or Light Detection and Ranging) uses integration of airborne laser and global position system (GPS) technology to measure difference in elevation of just 2 feet! A real plus in the Red River Valley where elevation in some areas varies less than 5 feet. How’s it done? Laser pulses are directed at the earth’s surface (early spring or late fall) from equipment aboard an aircraft flying a predetermined grid over an area of interest. The laser reflections are recorded and the range is calculated from the instrument’s orientation in space and the time required for the laser’s light reflection to travel back to the airplane. Examples below of the profile data.
The graph above was made from two original elevation profiles. The blue line is the elevation profile from Detroit Lakes to the Red River (taken as a straight line) and the red line is the elevation profile from Roseau to the Red River. Note that the Red River itself is dropping as it moves north, being at an elevation around 900 feet west of DL, and dropping nearly 100 feet when it gets west of Roseau. Detroit Lakes itself is at an elevation several hundred feet higher than Roseau.
The two profiles above are taken directly from the profile maker on the LiDAR website located at gis.rrbdin.org/lidarviewer. Creating a profile is easy, go ahead, play with it and see what new information you learn!
As we zoom in on locations, we can see more detail in the profile. Below is a profile of the elevation from Manvel, ND to the Red River – a distance of about 3.1 miles. The drop is only a foot or two, until you get to the Red River itself. The first big dip is where the transect crossed the South Marais River, the second is the Red River.