How To Use Srtm Data Version 2

How to use SRTM Data V2 for Preliminary Design New Railway Plan A short brief for Mr. Hiroki Sakaue and Mr. Takashi Odan at JTC by Irwan Joe

SRTM DATA The Shuttle Radar Topography Mission (SRTM) is an international research effort that obtained digital elevation models on a near-global scale from 56°S to 60°N, to generate the most complete high-resolution digital topographic database of Earth to date. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during the 11-day STS-99 mission in February of 2000. To acquire topographic (elevation) data, the SRTM payload was outfitted with two radar antennas. One antenna was located in the Shuttle's payload bay, the other on the end of a 60meter (200-foot) mast that extended from the payload bay once the Shuttle was in space. The technique employed is known as Interferometric Synthetic Aperture Radar. The elevation models are arranged into tiles, each covering one degree of latitude and one degree of longitude, named according to their south western corners. It follows that "n45e006" stretches from 45°00′N, 6°00′E to 46°00′N, 7°00′E and "s45w006" from 45°00′S, 6°00′W to 44°00′S, 5°00′W. The resolution of the cells of the source data is one arc second, but 1" data have only been released over United States territory; for the rest of the world, only three arc second data are available. Each one arc second tile has 3,601 rows, each consisting of 3,601 16 bit bigendian cells. The dimensions of the three arc second tiles are 1201 x 1201. The elevation models derived from the SRTM data are used in Geographic Information Systems. They can be downloaded freely over the internet, and their file format (.hgt) is supported by several software developments. The Shuttle Radar Topography Mission is an international project spearheaded by the U.S. National Geospatial-Intelligence Agency (NGA) and the U.S. National Aeronautics and Space Administration (NASA). NASA has released version 2 of the Shuttle Radar Topography Mission digital topographic data (also known as the "finished" version). Version 2 is the result of a substantial editing effort by the National Geospatial Intelligence Agency and exhibits well-defined water bodies and coastlines and the absence of spikes and wells (single pixel errors), although some areas of missing data ('voids') are still present. The Version 2 directory also contains the vector coastline mask derived by NGA during the editing, called the SRTM Water Body Data (SWBD), in ESRI Shapefile format. The data may be obtained by anonymous ftp to: ftp://e0srp01u.ecs.nasa.gov and moving to the directory srtm where both version 1 and version 2 directories may be found.

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Figure 1. The map of Java Island based on SRTM V2 Data

MAKING A RAILWAY DESIGN For this brief, a new railway design for Notog - Kebasen, Purwokerto - Kroya Line in Central Java is used for an example. The minimum requirement software is: 1) Global Mapper ( http://www.globalmapper.com ) 2) Autodesk Land Development and Civil Design Module, minimum version 2000 The minimum requirement data are: 1) SRTM Data for project location 2) Topographic Map from US ARMY 1:250000 or Bakosurtanal 1:25000 or 1:50000 paper copy. Download the SRTM Data The SRTM Data V2 can be downloaded at ftp://e0srp01u.ecs.nasa.gov or through the USGS seamless server at http://seamless.usgs.gov/

Figure 2 The Java SRTM's File

Making a Contour Map Before rectifying the image map, Global Mapper Software must be installed in the computer. 1) The paper map must be scanned first and convert it to image file (JPG or TIFF) 2

2) Run Global Mapper 3) The Java's Longitude coordinate is from 105º to 115º. It is across UTM's border at 108º. So we have to take only one zone for UTM coordinate. For this sample, we choose UTM Zone 48. 4) Open the SRTM V2 data for Java Island

5) Open the rectified image map

6) Generate the contour line at specific area (for example every 5 meter)

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7) Export the contour line to DXF format 8) Open the DXF file in Autodesk Civil

9) Change the color to " By layer" settings and make a surface terrain 10) Make a alignment 11) Generate long section of existing ground and make a design profile

12) Generate cross section of existing ground and attach the cross section template

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13) Calculate the earth work volume

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