The National Map Seamless Server, Earth Resources Observation and Science (EROS)
Description The National Elevation Dataset (NED) 1/9 Arc Second is a raster product assembled by the U.S. Geological Survey (USGS. NED 1/9 Arc Second is designed to provide National elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections are made in the NED 1/9 Arc Second assembly process to minimize, but not eliminate, artifacts, perform edge matching, and fill sliver areas of missing data. NED 1/9 Arc Second has a resolution of 1/9 arc-second (approx. 3m. NED 1/9 Arc Second data source is Light Detection and Ranging (LIDAR)data. The initial release includes Puget Sound, WA. In the NED 1/9 Arc Second assembly process the elevation values are converted to decimal meters as a consistent unit of measure, NAD83 is consistently used as horizontal datum, and all the data are recast in a geographic projection. As more data are acquired, they will be incorporated into the 1/9 Arc Second NED. To see the areas where the seamless product is available, at the map interface click on the 1/9 NED Index. Specifications
Format Information ArcGrid is an Arc/Info proprietary format. Some other software packages can read the ArcGrid format. Customers who specify ArcGrid will be delivered a workspace. The workspace is not tarred or gzipped. BIL is a non-proprietary format made by running the GRIDIMAGE command in Arc. The data is a simple binary raster format (signed integer data). There is an accompanying ASCII header file that provides file size information (number of rows and columns). The data are stored in row major order (all the data for row 1, followed by all the data for row 2, etc.). GridFloat is a non-proprietary format made by running the GRIDFLOAT command in Arc. The 32-bit (4 byte) is a simple binary raster format (floating point data). There is an accompanying ASCII header file that provides file size information (number of rows and columns). The data are stored in row major order (all the data for row 1, followed by all the data for row 2, etc.). More information about binary floating point is at:
TIFF for NED 1/9 Arc Second is a 32 bit floating point grid format. More information on the 32 bit floating point TIFF is at: Download Information
* Bil is a binary integer point format ** TIFF is a 32 bit floating point grid format *** GridFloat is a binary floating point format |
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U.S. Department of the Interior |
U.S. Geological Survey
URL: http://seamless.usgs.gov/products/9arc.php
Page Contact Information: webmapping@usgs.gov
Page Last Modified: November 22, 2007
