What are the NED data sources?
NED source data are selected from an ever-growing inventory of standard production USGS Digital Elevation Model (DEMs), and also from an increasing number of datasets that are project- or agency-specific. The first consideration is always given to quality. Selections are made according to the following ranking, listed in order of descending priority: • High-resolution data, typically derived from lidar or digital photogrammetry, and often with edited water bodies. If collected at a ground sample distance no coarser than 5 meters, such data may also be offered within the NED at a resolution of 1/9th arc-second. • Moderate-resolution data, other than that compiled from cartographic contours. These data may also be derived from lidar or digital photogrammetry, or less often by Interferometric Synthetic Aperture Radar IFSAR. A typical ground sample distance is 10 meters, though it is commonly called 1/3 arc-second data. • 10-meter DEMs derived from cartographic contours and mapped hydrogra
