- SPLAT! imports topographic data in the form of SPLAT Data
- Files (SDFs) that may be generated from a number of infor-
- mation sources. In the United States, SPLAT Data Files
- are most often derived from U.S. Geological Survey Digi-
- tal Elevation Models (DEMs) using the usgs2sdf utility
- included with SPLAT!. USGS Digital Elevation Models com-
- patible with this utility are available at no cost via the
- Internet at: http://edc-
- sgs9.cr.usgs.gov/glis/hyper/guide/1_dgr_dem-
- fig/index1m.html.
-
- SPLAT Data Files contain topographic elevations to the
- nearest meter above mean sea level for 1-degree by
- 1-degree regions of the earth with a resolution of 3-arc
- seconds. SDF files can be read in either standard format
- (.sdf) as generated by the usgs2sdf utility, or in bzip2
- compressed format (.sdf.bz2). Since uncompressed files
- can be slightly faster to load than compressed files,
+ SPLAT! imports topographic data in the form of SPLAT Data
+ Files (SDFs). These files may be generated from a number
+ of information sources. In the United States, SPLAT Data
+ Files can be generated through U.S. Geological Survey
+ Digital Elevation Models (DEMs) using the usgs2sdf utility
+ included with SPLAT!. USGS Digital Elevation Models com-
+ patible with this utility may be downloaded from:
+ http://edcftp.cr.usgs.gov/pub/data/DEM/250/.
+
+ Significantly better resolution can be obtained through
+ the use of SRTM-3 Version 2 digital elevation models.
+ These models are the result of the STS-99 Space Shuttle
+ Radar Topography Mission, and are available for most popu-
+ lated regions of the Earth. SPLAT Data Files may be gen-
+ erated from SRTM data using the included srtm2sdf utility.
+ SRTM-3 Version 2 data may be obtained through anonymous
+ FTP from: ftp://e0srp01u.ecs.nasa.gov:21/srtm/version2/
+
+ Despite the higher accuracy that SRTM data has to offer,
+ some voids in the data sets exist. When voids are
+ detected, the srtm2sdf utility replaces them with corre-
+ sponding data found in existing SDF files (that were pre-
+ sumably created from earlier USGS data through the
+ usgs2sdf utility). If USGS-derived SDF data is not avail-
+ able, voids are handled through adjacent pixel averaging,
+ or direct replacement.
+
+ SPLAT Data Files contain integer value topographic eleva-
+ tions (in meters) referenced to mean sea level for
+ 1-degree by 1-degree regions of the earth with a resolu-
+ tion of 3-arc seconds. SDF files can be read in either
+ standard format (.sdf) as generated by the usgs2sdf and
+ srtm2sdf utilities, or in bzip2 compressed format
+ (.sdf.bz2). Since uncompressed files can be processed
+ slightly faster than files that have been compressed,