Elevation - 8 of 39
Elevation FAQs - 39 Found
There are frequently multiple sources of elevation data that cover a given location. Preference is given to that which is the most detailed and up-to-date, unless there are overriding quality concerns. An important qualification is that any candidate source data be freely redistributable. Data source requirements for the NED 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*.
* NED seamless layers represent a topographic surface. Hydro-flattening is necessary for any dataset to be considered for the NED seamless layers. Currently, non hydro-flattened data are accepted into the 1/9 arc-second layer only if they are in a location where there are no other data available to the public. NED 1/9 arc-second data will not migrate to the other seamless layers unless they are hydro-flattened. Hydro-enforced or hydro-conditioned DEM data create surfaces that are not suitable for topographic mapping, and are not considered suitable for seamless NED layers.