Regional CRS Essentials

NAD83¶

USGS 3DEP uses NAD83 + NAVD88 Heights. This is not a global system and rather focuses on CONUS and US Territories. Here we focus on the continental US (CONUS) where NAD83 defines a coordinate system that moves with the North American plate. It’s refered to as ‘static’ because to an observer measuring positions on the plate, the plate is not moving :)

Just like WGS and ITRF, there are different, increasingly accurate “realizations” of the NAD83 datum over time:

NAVD88 (EPSG: 5703)¶

To be updated ~2025: with geopotential datum will be called North American-Pacific Geopotential Datum of 2022 (NAPGD2022). The most prominent of these products will be a time-dependent model of the geoid, provided in three regions (the first covering the entirety of North and Central America, Hawaii, Alaska, Greenland, and the Caribbean; the second covering American Samoa; and the third covering Guam and the Commonwealth of the Mariana Islands). The name of this model will be GEOID2022. Read more: https://www.ngs.noaa.gov/datums/newdatums

Projected CRS¶

Universal Transverse Mercator¶

UTM is a cylindrical map projection that divides the Earth into 60 zones, each spanning 6 degrees longitude.Each UTM zone will have a corresponding CRS for the northern and southern hemispheres. Polar regions use universal polar stereographic (UPS) projections, as UTM projections become distorted above 84°N and below 80°S.

• Northern Hemisphere EPSG = prefix 326 + zone #
• Southern Hemisphere EPSG = prefix 327 + zone #

To figure out a UTM Zone for any location, take the longitude add 180°, divide by 6, and round up! For example, Seattle, WA is at (-122.3°, 47.6°), so it’s UTM zone is 10N (EPSG:32610)

Polar Stereographic¶

https://nsidc.org/data/user-resources/help-center/guide-nsidcs-polar-stereographic-projection

• Southern Hemisphere: EPSG:3976
• Northern Hemisphere: EPSG:3413