What is the generation process for NED data?
The source DEMs are projected from their native coordinate system to the geographic coordinate system (decimal degrees of latitude and longitude) using standard cartographic transformation software. Both horizontal and vertical datums are addressed as well during NED processing. Resampling of the original elevation values is done with implementations of cubic convolution and bilinear interpolation in order to retain the integrity of shorelines and water bodies. All NED vertical elevations are reported in meters, so if the data are in other units a conversion is applied. The data are then mosaicked into a seamless layer and made available for user view and download.
