Contents
What is 1/3 arc second DEM?
1/3 arc-second – This is the highest resolution seamless DEM dataset for the U.S. with full coverage of the 48 conterminous states, Hawaii, and U.S. territories. Alaska coverage is partially available now and is being expanded to statewide coverage as part of the Alaska Mapping Initiative.
What is 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 is an arc second a measure of?
Each degree is subdivided into 60 minutes. Each minute is composed of 60 seconds. Said differently, an arc-second represents the distance of latitude or longitude traversed on the earth’s surface while traveling one second (1/3600th of a degree).
What is the distance of one second in latitude?
Degrees of latitude are divided into 60 minutes. To be even more precise, those minutes are divided into 60 seconds. One minute of latitude covers about 1.8 kilometers (1.1 miles) and one second of latitude covers about 32 meters (105 feet).
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).
How many arc seconds are in Ned 30?
In some cases, the 10m NED is resampled from LIDAR or created using aerial photography. NED 30(One arc-second approximately 3o meters) The 30 meter NED is ~1 arc-second data that is updated over large areas by integrating the 10 meter or better source data(where available), re-sampled to 1 arc-second.
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.