Using ArcGIS to Process and Analyze Lidar Data for Rhode Island

Seven Rhode Island Army National Guard Range sites (active and inactive) were selected for the collection of lidar elevation data to be used for training maps and to assess environmental impacts of current and possible future training areas.

Both raw lidar data points (LAS file format of last and return data points) and an ASCII file of grid points representing an interpolated grid of bare-earth data classifications were converted to multipoint feature classes using the LAS and ASCII conversion tools available in ArcGIS 9.2. Raster elevation grids were created from all multipoint feature classes. After editing, the data was checked for density consistency in open canopy areas (e.g., parking lots and open fields). Each tile was then checked to make sure noise and vegetation points have been removed.

The Quonset Point elevation maps illustrate the different data types. Map A shows the raw bare-earth digital elevation model (DEM), generated from the raw lidar data. Map B shows the interpolated bare-earth grid. Map C represents the last return grid. For Map D, using the ArcGIS Raster Calculator, the last return grid was subtracted from the bare-earth grid, resulting in a DEM of building heights and height of vegetation patches.

Courtesy of Tracey Daly and the University of Rhode Island, Environmental Data Center.