A USGS DEM can be classified into one of four levels of quality. This is due to the multiple methods of data collection, and certainty in the data.
| DEM level | DEM series | Production process | Comments |
|---|---|---|---|
| Level 1 | 7.5-minute 30-minute |
Created by autocorrelation or manual profiling from aerial photographs | May be derived from a wide variety of sources using any of a number of USGS approved techniques and instrumentation |
| Level 2 | All series | Created from digital line graph (DLG) contours or equivalent, from any USGS map series up to 1:100000 scale | The accuracy and data spacing are intended to support computer applications that analyze hypsographic features to a level of detail similar to manual interpolations of information from printed source maps |
| Level 3 | 7.5-minute | Created from DLG that have vertically integrated with all categories of hypsography, hydrography, ridge line, break line, drain files, and all vertical and horizontal control network | Requires a system of logic to interpret the data |
| Level 4 | All series | Created from electronic (non-photogrammetric) imaging sensor systems, either active (e.g., radar or lasar) or passive (received radiant energy) | The process includes all additional post-processing required to bring the DEM grid to its final form |
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