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Library Research Guides

Geospatial Data

Subject guide to finding and using geospatial data. Includes tutorials for using elevation data to make contours, and using aerial imagery layers to output imagery even more efficiently than Google Earth Pro can.

US Sources

3DEP data from the USGS (which has superceded the National Elevation Dataset (NED)

Access through The National Map .

Raster resolution is 1 arc-second (approximatelly 1 point every 30 meters) and 1/3 arc-second (approximately 1 point every 10 meters) for most areas. Some areas have higher resolution data, at 1/9 arc-second (1 point every 3 meters), including SE Michigan. Data for Alaska is at a different resolution.

Contours are available at a scale of 1:24000. This is suitable for mapping at somewhere around the size of a neighborhood or town. Contours at this scale will not be detailed enough for small areas, like a city block, and will have too much detail for representing topography over larger areas. For smaller areas, try downloading raster data at the 1/3 or 1/9 arc-second, and deriving your own contours. For larger areas, a number of approaches can work, including contours available from The National Map at the 1:1million scale (see the Small-scale Datasets section).

Local governments (state, county, municipality) may have additional higher-quality data that is not available from The National Map, and these can included LiDAR-derived DEMs, more detailed contours, or other forms of data.

World Data Sources


You can download data from the REVERB/ECHO viewer - really great global resolution!


SRTM data is only available for areas between latitudes 60 S and 60 N.