LiDAR (Light Detection and Ranging) uses laser pulses to accurately gather horizontal and vertical positions by collecting data from instruments attached to aircraft, satellite, or leveled on a tripod for terrestrial surveys.
The data can be stored as an LAS or ASCII file and then converted to a multipoint feature using a Geographical Information System (GIS) such as ArcMap 10.0.
The multipoints can be converted into a raster and displayed as a Digital Elevation Model (DEM).
The resolution of the resulting raster depends on the density of the points. A raster cell that does not contain any multipoints will result as a no data cell. Therefore, it is often recommended to choose a raster size four-times the size of average point spacing.
Through experimentation using different interpolation techniques, it has been found that a raster cell size equal to or slightly less than the reported average point spacing can be used to represent the multipoint feature class as a raster.
The following images illustrate the results of this experimentation:
Fig.1 Digital Elevation Model of Zoar Valley. located east of Gowanda, NY. The DEM has a resolution of 5′ and the white areas represent no data.
Fig. 2 DEM of Zoar Valley after calculating elevation for raster cells containing no data.
Fig. 3 DEM with a hillshade raster overlay.
LiDAR derived data can also be used to map building and vegetation heights. Increasing the resolution of the raster will enhance the representation of building and vegetation features.
Fig. 4 3m Resolution of the National Palace, Port-au-Prince, Haiti
Fig. 5 National Palace at a resolution of 0.5m before values for raster cells containing no data have been calculated.
Fig. 6 National Palace at a resolution of 0.5m after values for raster cells containing no data have been calculated.
LiDAR also collects the light intensity of ground objects. A raster similar to a black and white aerial photograph can be derived from the data.
Fig. 7 Intensity raster of the National Palace at a resolution of 0.5m.
Fig. 8 National Palace, Port-au-Prince, Haiti at 0.5m resolution.
Fig. 9. 0.25 m Resolution Digital Surface Model, University of Colorado Boulder.
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