Most computer-based models of elevation are based on relatively few measured points, usually with considerable distance between them. With the development of airborne LiDAR, knowledge of surface elevation has increased dramatically: Elevation points on the surface (x, y, and z) can be spaced horizontally approximately two or three meters apart! GIS LiDAR (Light Detection and Ranging)34
datasets are collected by aircraft using light from lasers that is bounced off the earth’s surface and returns to the aircraft. The time it takes for this round trip is precisely recorded and used to determine the distance from the aircraft to the ground. Combined with other information, the elevation of the point on the ground can be calculated.
In the following exercise, you will add a LiDAR dataset to your map and look at a few of its properties. LiDAR is not an image or a photograph but resembles both because, in addition to obtaining elevation data, different surfaces return different amounts of the laser beam, so that objects or conditions can be discerned from a LiDAR dataset.
Start a new, blank map in ArcMap. From the [___]IGIS-Arc\River folder add as data the GPS track. Click Add Data again and, in the same folder, you will find the File Geodatabase Terrain_from_LIDAR.gdb. Double-click it. Add
to the map. Zoom to the extent of this File Geodatabase terrain.