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The NED dataset is a compilation of data from a variety of existing high-precision datasets such as LiDAR data (see also National LIDAR Dataset - USA), contour maps, USGS DEM collection, SRTM and other sources which were reorganized and combined into a seamless dataset, designed to cover all the United States territory in its continuity.
The USGS DEM format is a self-contained (single file) set of ASCII-encoded (text) 1024-byte (1024 ASCII chars) blocks that fall into three record categories called A, B, and C. There is no cross-platform ambiguity since line ending control codes are not used, and all data including numbers is represented in readable text form.
The data was entered in spreadsheet format or in ESRI shapefiles and submitted via e-mail to the USGS National Geospatial Technical Operations Center(s) in Denver, Colorado, and Rolla, Missouri. During the registration process, prospective volunteers submitted a list of the 7.5 minute quadrangle maps on which they wished to work.
A digital elevation model (DEM) or digital surface model (DSM) is a 3D computer graphics representation of elevation data to represent terrain or overlaying objects, commonly of a planet, moon, or asteroid.
Online collection of all digital USGS 1:24K scale topographic maps (as well as various other GIS data) covering the United States, available as a free download. NPScape United States Department of the Interior National Park Service NPScape is a landscape dynamics monitoring project that provides landscape-level data, tools, and evaluations for ...
GTOPO30 is a digital elevation model for the world, developed by United States Geological Survey (USGS). It has a 30-arc second resolution (approximately 1 km), [1] and is split into 33 tiles stored in the USGS DEM file format. According to DTED and USGS DEM the absolute vertical accuracy of GTOP30 varies from ±30 meters. [2]
Between 1995 and 1998 the dlgv32 application was expanded to include support for viewing other USGS data products, including DRG (topographic maps) and DEM (digital elevation model) and SDTS-DLG and SDTS-DEM data products. [4] The development process is described in detail in the USGS paper titled 'A Programming Exercise'.
USGS HydroSHEDS – Full resolution SRTM-based DEM for hydrological applications; Software that can read and process SRTM data: 3dem, GRASS GIS, SAGA GIS, MapWindow GIS, DG Terrain Viewer/Void Killer, Virtual Terrain Project; Viewfinder Panoramas – Unofficial SRTM data with voids corrected using topographic maps