Contents
What is a 1 arc second DEM?
The seamless 1 arc-second DEM layer provides coverage of the conterminous United States, Hawaii, Puerto Rico, other territorial islands, and much of Alaska and Canada. The seamless 1 arc-second DEM is available as pre-staged products tiled in 1 degree blocks in Erdas .
What distance is 1 second of latitude?
101 feet
One degree of latitude equals approximately 364,000 feet (69 miles), one minute equals 6,068 feet (1.15 miles), and one-second equals 101 feet.
How many arcseconds is the moon?
60 arcseconds
An arcminute can also be divided into 60 arcseconds (abbreviated 60 arcsec or 60″). The angle covered by the diameter of the full moon is about 31 arcmin or 1/2°, so astronomers would say the Moon’s angular diameter is 31 arcmin, or the Moon subtends an angle of 31 arcmin.
How tall is an arc second in Ned?
As part of its National Map initiative, the USGS has developed a suite of elevation products derived from traditional DEMs, lidar, and other sources. NED data are available at three resolutions: 1 arc second (approximately 30 meters), 1/3 arc second (approximately 10 meters), and 1/9 arc second (approximately 3 meters).
Where are the 1 / 3 arc-second digital elevation models located?
All elevation values are in meters and, over the continental United States, are referenced to the North American Vertical Datum of 1988 (NAVD88). The seamless 1/3 arc-second DEM layer provides coverage of the conterminous United States, Hawaii, Puerto Rico, other territorial islands, and in limited areas of Alaska.
Is the 1 / 3 arc-second DEM available in ERDAS?
The seamless 1/3 arc-second DEM is available as pre-staged products tiled in 1 degree blocks in Erdas .img, ESRI arc-grid, and grid float formats. The seamless 1/3 arc-second DEM layer is updated continually as new data become available.
Where does the 1 / 3 arc-second dem layer come from?
The seamless 1/3 arc-second DEM layers are derived from diverse source data that are processed to a common coordinate system and unit of vertical measure. These data are distributed in geographic coordinates in units of decimal degrees, and in conformance with the North American Datum of 1983 (NAD 83).