LiDAR data from the Minnesota Department of Natural Resources is now available for the entire Twin Cities metro area! LiDAR (Light Detection And Ranging) data is collected by airplanes equipped with special equipment which shoot laser light beams at the ground. By measuring how quickly the light beams are reflected back from the ground the equipment is able to get a highly accurate measurement of the ground’s elevation. A DEM (Digital Elevation Model) is then created with an impressive resolution of 1 meter, which is eventually converted into 2-foot topographic contour lines for displaying on maps.
Data is available from the DNR in 1.5 mile x 2.25 mile sections, or “tiles”. Flat Rock has used this data to calculate slope, aspect, and elevation. A hillshade image is also created which gives a simulated 3-D view of the surface. So far we have processed areas for the cities of Andover, Columbia Heights and Fridley and the Coon Creek Watershed District.
Even in the case of this highly accurate LiDAR data, there is still a possibility for error. The DNR has implemented rigorous, county-by-county validation checks using survey-grade GPS. If the initial LiDAR data did not meet accuracy requirements, the area was reflow. Accuracy Reports are available for every county.