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Elevation Data

Massachusetts

MassGIS Data – LiDAR Terrain Data Contains the latest datasets of Light Detection and Ranging (LiDAR) terrain files covering most of eastern Massachusetts.

US Elevation Data

USGS – National Elevation Data Set for the US, this is the primary source of digital elevation models, including SRTM data (for the US only – for international SRTM data, see the links described in the SRTM section below). Note some US states will have elevation data available at even higher resolution (e.g., MassGIS has a 5m DEM, plus contour lines), so check with the state clearinghouse as well.

Global Elevation Data

GTOPO

GTOPO has 1 km x 1km digital elevation models available for the entire world. These are 1 km digital elevation models – not high resolution but good for creating generalized maps of large regions and continents – created from paper maps.

Aster Global DEM Data

Aster Global Digital Elevation Model Map -this is a 30m DEM product, made freely available through a joint US-Japan program using the Aster satellite sensor. The web site has instructions for how to download.

Shuttle Radar Topography Mission (SRTM) data

SRTM data was acquired by the US Shuttle in February 2000. The data provides elevation values in a raster DEM format for most of the globe at 90m cell size. To learn about SRTM data, go to the NASA SRTM site.

The USGS distributes the SRTM data and has more information about it – https://lta.cr.usgs.gov/SRTM

The following sites have good access to international SRTM data and in the case of the Hydrosheds program, to good derived hydrographic data as well:
  • USGS – Hydrosheds – Digital elevation models and hydrologic base data derived from the Shuttle Radar Topography Mission and other sources at 90 meter grid cell resolution – more detailed than the Hydro 1K data, but not available for the whole world yet (as of 5/1/2007, South America, Central America, and Asia are complete). See the web site for details on how the SRTM and other data sources were processed, and for status of other areas and expected completion dates. If you are looking for DEMs for areas outside the US, this should be your first choice. If not available here, go to the CGIAR SRTM site (below)
  • CIGIAR (Consortium for Spatial Information) – CIGIAR has a very easy interface for downloading finished (void-filled) SRTM 90 meter digtial elevation models. Note, if you have trouble identifying your area on the small CGIAR map, you can click on the Google Earth SRTM KML link further down the CGIAR page to use Google Earth to locate your data more accurately. If you download GeoTiff format files (which work well in ArcGIS), make sure to follow the directions in the SRTM FAQ page (http://srtm.csi.cgiar.org/SRTM_FAQ.asp) regarding fixing the problem with cell values of -32768. These values should be set to NO DATA. The FAQ explains what equation to use (OUTGRID = setnull(SRTMDEM == -32768, SRTMDEM) – you can use this equation in the Spatial Analyst Raster Calculator. Replace OUTGRID with the name of your new fixed SRTM tile (e.g., fix4210), and substitute the name of your original SRTM file for the “SRTMDEM” in the equation. E.g., for an SRTM called z_42_10.TIF that I downloaded, I used the following function in the Raster Calculator:
    fix4210 = setnull([GISDataSources:Z_42_10.TIF] == -32768, [GISDataSources:Z_42_10.TIF] This creates a new grid, fix4210, that has all values of -32768 set to No Data, and all other values set to whatever they were in the original SRTM DEM.

Also, note that you can use the Mosaic to New Raster command under the Data Management – Raster Toolbox in ArcGIS 9 to mosaic multiple tiles to a single raster. While you’re doing this, you should probably specify a projected coordinate system so that the other surface, hydro, etc. functions will work properly. |

LIDAR Data