TerreSculptor

HeightMap Editor Software

User Tools

Site Tools


digital_elevation_models

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

digital_elevation_models [2013/01/29 17:09] (current)
dgreen created
Line 1: Line 1:
 +=====Digital Elevation Model Support=====
 +
 +The following web sites are repositories for digital elevation model data that can be used with TerreSculptor.
 +
 +This page was last updated on October 03, 2011.  The information regarding these sites should be current as of this date.
 +
 +This list will be maintained and updated with information regarding the data file formats and their support with TerreSculptor. \\
 +Most DEM data is free for any use but be sure to check with each DEM site's data file usage policy before using any DEM data files for commercial purposes.
 +
 +Unfortunately, many of the DEM data sites are operated by governments or organizations who are constantly changing their data file formats and changing their data sets and web site addresses. \\
 +Comments regarding DEM data site additions or corrections can be posted by registered users on the TerreSculptor forums.
 +
 +====Choosing the Proper DEM Resolution====
 +
 +Digital Elevation Model resolution is typically specified in arc-seconds or meters between sample points. \\
 +The resolution value is the spacing distance between each altitude sample point, which is the equivalent to each pixel in a heightmap or each vertex in a terrain mesh. \\
 +The spacing can also be thought of as the size of each terrain quad triangle-pair. \\
 +A 10 meter DEM file is therefore three times higher resolution than a 30 meter DEM file. \\
 +To obtain a satisfactory terrain resolution for use in video games a resolution between 1 and 10 meters is typically required.
 +
 +Arc-seconds to Meters approximate conversion ratio for common resolutions: \\
 +30 arc-seconds = 900 meters (approximately 1 kilometer) \\
 +10 arc-seconds = 300 meters \\
 +3 arc-seconds = 90 meters \\
 +1 arc-second = 30 meters \\
 +1/3 arc-second = 10 meters \\
 +1/9 arc-second = 3 meters
 +
 +Spacing as related to video game engine terrain meshes:
 +
 +- A terrain mesh with an XY spacing of 128 and an engine unit of 1 unit = 1cm is a spacing of 128cm or a 1.28 meters DEM spacing. \\
 +- A terrain mesh with an XY spacing of 256 and an engine unit of 1 unit = 1cm is a spacing of 256cm or a 2.56 meters DEM spacing. \\
 +- A terrain mesh with an XY spacing of 512 and an engine unit of 1 unit = 1cm is a spacing of 512cm or a 5.12 meters DEM spacing.
 +
 +- A terrain mesh with an XY spacing of 128 and an engine unit of 1 unit = 2cm (Epic UDK) is a spacing of 256cm or a 2.56 meters DEM spacing. \\
 +- A terrain mesh with an XY spacing of 256 and an engine unit of 1 unit = 2cm (Epic UDK) is a spacing of 512cm or a 5.12 meters DEM spacing. \\
 +- A terrain mesh with an XY spacing of 512 and an engine unit of 1 unit = 2cm (Epic UDK) is a spacing of 1024cm or a 10.24 meters DEM spacing.
 +
 +- A DEM spacing of 1/9 arc second (3 meters) and an engine unit of 1 unit = 2cm (Epic UDK) is an XY spacing of 150 (128 is the closest power-of-two value). \\
 +- A DEM spacing of 1/3 arc second (10 meters) and an engine unit of 1 unit = 2cm (Epic UDK) is an XY spacing of 500 (512 is the closest power-of-two value).
 +
 +----
 +
 +====DEM Data Sites====
 +
 +The following is a partial listing of DEM sites that host data files.
 +
 +\\
 +===CGIAR - Consortium for Spatial Information===
 +
 +Main URL: http://srtm.csi.cgiar.org/ \\
 +Resolutions: 3 arc-seconds (90 meter) \\
 +Formats: GeoTIFF, ArcInfo ASCII \\
 +TerreSculptor: currently not supported (ArcInfo ASCII support is currently under development)
 +
 +\\
 +===Earth Explorer - USGS===
 +
 +Main URL: http://edcsns17.cr.usgs.gov/NewEarthExplorer/
 +
 +Additional information will be added soon.
 +
 +\\
 +===EROS - Earth Resources Observation and Science (EROS) Center===
 +
 +Main URL: http://eros.usgs.gov/#/Find_Data/Products_and_Data_Available/gtopo30_info \\
 +Resolutions: 30 arc-second (1 kilometer) \\
 +Formats: BIL (Motorola signed 16-bit integer with .hdr file) \\
 +TerreSculptor: import BIL with .hdr
 +
 +Rename the .DEM file in the download to .bil and import it as BIL. \\
 +The .HDR text file contains the BIL file meta-information.
 +
 +NOTE! Tests of the data files from this site show that they are incorrect and cannot be successfully loaded. \\
 +The .HDR file meta-information does not equal the data file contents. \\
 +This issue will be examined further and information posted here.
 +
 +\\
 +===GeoBase - Canadian Digital Elevation Data===
 +
 +Main URL: http://www.geobase.ca/geobase/en/data/cded/index.html \\
 +Resolutions: vary from 0.75 arc-seconds (22 meter) to 12 arc-seconds (360 meter) \\
 +Formats: ASCII DEM \\
 +TerreSculptor: currently not supported (ASCII DEM support is currently under development)
 +
 +\\
 +===NASA PDS Geosciences Node===
 +
 +MOLA - Mars Global Surveyor
 +
 +Main URL: http://pds-geosciences.wustl.edu/missions/mgs/megdr.html \\
 +Resolutions: low \\
 +Formats: .img binary
 +
 +The topography .img files can be manually loaded with the TerreSculptor Raw R16 importer. \\
 +Rename the .img file to .r16. \\
 +Proper .img file format support is coming soon.
 +
 +Meg4 4 pixels per degree megt* is topology 1440x720 16-bit signed Mac \\
 +Meg16 16 pixels per degree megt* is topology 5760x2880 16-bit signed Mac \\
 +Meg32 32 pixels per degree megt* is topology 11520x5760 16-bit signed Mac \\
 +Meg64 64 pixels per degree megt* is topology 11520x5760 16-bit signed Mac \\
 +Meg128 128 pixels per degree megt* is topology 11520x5632 16-bit signed Mac
 +
 +Polar 512 pixels per degree megt* is topology 12288x12288 16-bit signed Mac
 +
 +Meg128 total 4x4 tile images for 46080x22528 x16bit = 2,076,180,480 \\
 +The top and bottom strips are essentially useless as they are stretched due to projection so: \\
 +total 2x4 tile images for 46080x11264 = 519045120 x16bit = 1,038,090,240
 +
 +\\
 +===NASA PDS Geosciences Node===
 +
 +Magellan - Venus Magellan GTDR Topographical Data records.
 +
 +Main URL: http://pds-geosciences.wustl.edu/missions/magellan/gxdr/index.htm \\
 +Resolutions: low \\
 +Formats: .img binary
 +
 +The topography .img files can be manually loaded with the TerreSculptor Raw R16 importer. \\
 +Rename the .img file to .r16. \\
 +Proper .img file support is coming soon.
 +
 +Browse.img files are 512x512 with 2048 header. \\
 +f*.img files are 1024x1024 16-bit with 2048 header.
 +
 +\\
 +===NED - USGS National Elevation Dataset.===
 +
 +Main URL: http://ned.usgs.gov/ \\
 +Data viewer URL: http://seamless.usgs.gov/website/seamless/viewer.htm \\
 +Datasets: United States \\
 +Available resolutions:
 +
 +NED 1 (1 arc-second = 30 meter) \\
 +Formats: ArcGrid, Bil, Bil_16 Integer, TIFF, GridFloat \\
 +TerreSculptor: import Bil 16-bit Integer and Gridfloat
 +
 +NED 1/3 (1/3 arc-second = 10 meter) \\
 +Formats: ArcGrid, Bil, Bil_16 Integer, TIFF, GridFloat \\
 +TerreSculptor: import Bil 16-bit Integer and Gridfloat
 +
 +NED 1/9 (1/9 arc-second = 3 meter) \\
 +Formats: ArcGrid, Bil, Bil_16 Integer, TIFF, GridFloat \\
 +TerreSculptor: import Bil 16-bit Integer and Gridfloat
 +
 +\\
 +===SRTM - Shuttle Radar Topography Mission===
 +
 +Main URL: http://srtm.usgs.gov/
 +
 +Requires onsite user account registration and login. \\
 +Additional information will be added soon.
 +
 +\\
 +===Miscellaneous DEM URLs===
 +
 +http://www.mcgill.ca/library/library-findinfo/maps/dem/
 +
 +http://www.solarviews.com/cap/mars/marscyl2.htm
 +
 +http://www2.jpl.nasa.gov/srtm/
 +
 +
 +-eof-
  
digital_elevation_models.txt ยท Last modified: 2013/01/29 17:09 by dgreen