NEWS NOTES ON SUSTAINABLE WATER RESOURCESDigital Elevation Modelshttps://www.usgs.gov/faqs/what-are-digital-elevation-models-dems?qt-news_scienc...
Published on by Tim Smith, Employee at Retiree & P/T Consultant
Digital Elevation Models
https://www.usgs.gov/faqs/what-are-digital-elevation-models-dems?qt-news_science_products=0#qt-news_science_products
“USGS Digital elevation models (DEMs) are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. The USGS acquires bare-earth elevation source data through the 3D Elevation Program (3DEP) and resamples the data to several National Map DEM products for the U.S. and territories. The DEM products include 2, 1, 1/3, and 1/9 arc-second layers, as well as 5-meter DEMs in Alaska and 1-meter DEMs in the conterminous U.S. The 2, 1, and 1/3 arc-second DEMs are logically seamless terrain surfaces in their respective areas of coverage and are produced from the highest quality elevation data held by the USGS.”