What is the general process for NED and how does this fit into The National Map?
National Elevation Dataset (NED) Process The NED is in fact the elevation data theme of The National Map .Internally, we produce new DEMs, and fix bad DEMs (from customer reports) for archival into the GDA. The Sales Data Base retrieves all new uploads from the GDA, whether they are new or replacements. But more importantly, the NED also retrieves new uploads from the GDA. These uploads contribute to maintaining a current version of the NED in a seamless environment for The National Map . In basic terms, the NED upload process converts archive DEM data into the geographic format of arc-seconds, cast on the datums of NAD83 and NAVD88. The conversion process takes into account all horizontal and vertical datums, as well as many map projections that our DEM data holdings represent for both the past and present.
A. National Elevation Dataset (NED) Process: The NED is in fact the elevation data theme of The National Map. Internally, we produce new DEMs, and fix bad DEMs (from customer reports) for archival into the GDA. The Sales Data Base retrieves all new uploads from the GDA, whether they are new or replacements. But more importantly, the NED also retrieves new uploads from the GDA. These uploads contribute to maintaining a current version of the NED in a seamless environment for The National Map . In basic terms, the NED upload process converts archive DEM data into the geographic format of arc-seconds, cast on the datums of NAD83 and NAVD88. The conversion process takes into account all horizontal and vertical datums, as well as many map projections that our DEM data holdings represent for both the past and present.