Elevation - 8 of 41
Elevation FAQs - 41 Found
There are frequently multiple sources of elevation data held by the USGS that cover a given geographic location. In generation of the seamless DEMs, preference is given to that which is the most detailed and up-to-date, unless there are overriding quality concerns. Data source requirements for the seamless layers are listed below:
- Bare-earth elevation surface
- Highest resolution USGS source for an area
- Most recent USGS source for an area
- Most accurate USGS source for an area
- Freely redistributable
- Hydro flattened*
- Must not be hydro-enforced or hydro-conditioned*.
* National Map seamless layers represent a topographic surface. Hydro-flattening is necessary for any dataset to be considered for the seamless layers. Hydro-enforced or hydro-conditioned DEM data create surfaces that are not suitable for topographic mapping, and are not considered suitable for seamless DEMs.