So when the Illinois Department of Transportation began to move forward with a major contract to provide county-wide aerial photography & LiDAR data as part of the Illinois Height Modernization program, it quickly caught the eye of geospatial professionals from all types of industries, including our own. The question has been, how accurate will this LiDAR data be? By far the best explanation I heard was from one of IDOT's representatives when he said, "the accuracy of the LiDAR data has been challenged many times and each time the challenger returns to us with the same answer: OK, it's good enough". This, of course, really sparked my interest so when we recently acquired the draft data for Woodford County, I immediately got out my Trimble Geo XH 6000 (cm Edition) unit to take some sample GPS points. Here are my results
I collected the GNSS points at random locations with the Trimble unit, stripped out the GNSS_Height and gave it to Micah, saying "here, give me the elevations of these points using IDOT's LiDAR data." 10 minutes later after he extracted the elevations from ArcGIS, he read them aloud (shown in green) and I realized that the gentleman's statement of "It's good enough" is in fact, correct. This however, is my opinion and you are welcome to form your own.