On the CyberShARE site you will find this interpolated version (labeled SRTMv4_90m)

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1 SRTM Data on Cyber-ShARE The Shuttle Radar Topography Mission (SRTM) data collected by NASA represents the most up-to-date, globally collected topography data set of the Earth. It makes up the first globally continuous (60 degrees North to 60 degrees South) 90 m resolution data set, with 30 m resolution within the Unites States and its territories. In addition to providing a continuous data set, it also provides a global reference frame for the location and topography of islands, some of which have been substantially mis-located in existing databases. Cyber-ShARE hosts two versions of the SRTM dataset, stored in directories named SRTMv4_90m and SRTM30_PLUS_900m. Directions for accessing these versions are provided in the following pages. SRTMv4_90m: This dataset consists of several files of global land topography spanning latitudes 60N 60S at 90 m resolution. In the U.S., data is available at 30 m resolution. This particular version of SRTM data consists of the original 90m/30m NASA (finished) data, subsequently processed to fill the data voids. The data currently being distributed by NASA/USGS contains "no-data" holes where water or heavy shadow prevented the quantification of elevation. These are generally small holes, which nevertheless render the data less useful, especially in fields of hydrological modeling. Dr. Andrew Jarvis and Edward Guevara of the Center for International Tropical Agriculture - Land Use project, Dr. Hannes Isaak Reuter (JRC-IES-LMNH) and Dr. Andy Nelson (JRC-IES-GEM) all worked to produce this cleaned version of the SRTM dataset ( According to their website: This involved the production of vector contours, and the re-interpolation of these derived contours back into a raster DEM. The method allows for (i) the support for auxiliary information, (ii) the use of a void region specific processing over a tile based processing, (iii) use of SWDB V2 water body database, (iv) correction for vertical bias, (v) for areas with auxiliary high resolution DEM information a hydrologically correct DEM is generated based on the TOPOGRID procedure, (vi) for areas without a high resolution auxiliary DEM the most appropriate interpolation technique is selected based on void size and landform typology according to Reuter et al.(2007). These interpolated DEM values were then used to fill in seamlessly the no-data holes within the SRTM data. This was done using Arc/Info(R) and an AML script. The DEM files have been mosaiced into a seamless global coverage, and are available for download as 5 degree x 5 degree tiles, in geographic coordinate system - WGS84 horizontal and EGM96 vertical datum. These files are available for download in both Arc-Info ASCII format, and as GeoTiff, for easy use in most GIS and Remote Sensing software applications. In addition, a binary no data mask file is available for download, allowing users to identify the areas within each DEM which has been interpolated. We kindly ask any users to cite this data in any published material produced using this data. Please cite the dataset for the Version 4 as: Jarvis A., H.I. Reuter, A. Nelson, E. Guevara, 2008, Hole-filled seamless SRTM data V4, International Centre for Tropical Agriculture (CIAT), available from On the CyberShARE site you will find this interpolated version (labeled SRTMv4_90m)

2 in the ARCASCII format. Each file is named according to the bottom-left corner of each 5x5 degree panel. To convert these files to GMT GRD format, use the xyz2grd E flag in GMT. SRTM30_PLUS_900m: This dataset consists of 33 files of global topography (ocean bathymetry + land topography combined) spanning all N/S latitudes. Each file grid resolution is 30 arc-seconds, which is roughly 900 m, or 1 km. Land data are based on the 1- km averages of topography derived from the USGS SRTM30 gridded DEM data product created with data from the NASA Shuttle Radar Topography Mission. GTOPO30 data are used for high latitudes where SRTM_v4 data are not available. Ocean data are based on the Smith and Sandwell global 1- minute grid between latitudes +/- 81 degrees. Higher resolution grids have been added from the LDEO Ridge Multibeam Synthesis Project, the JAMSTEC Data Site for Research Cruises, and the NGDC Coastal Relief Model. Arctic bathymetry is from the International Bathymetric Chart of the Oceans (IBCAO) [Jakobsson et al., 2003]. The pixel-registered GRD (.grd) data are stored in 33 files with names corresponding to the upper-left corner of the array shown below, spanning 50 degrees in latitude and 40 degrees in longitude, except for the Antarctic, where grids span 30 degrees in latitude and 60 degrees in longitude. Using GMT, type grdinfo and the name of the.grd file to get a obtain information about each grid. To convert to ASCII files, issue the GMT command grd2xyz. GRD files can be read directly into MATLAB, Fledermaus, and GRASS programs.

3 Accessing SRTM data using Macs 1) Log into an Apple Computer (local login or VPN) VPN instructions at UTEP IT website: 2) From the Apple Toolbar click on Go 3) Click on Connect to Server: a. Enter: smb://geondata/srtm b. Press Connect 4) When prompted, enter your UTEP account password 5) When the server connects, two SRTM datasets should be available: SRTM30_PLUS_900M or SRTMv4_90m 6) When done, please disconnect from the network drive: a. Open any window in Finder b. From the Side bar, click the Eject button next to the geondata folder

4 Accessing SRTM data using Windows 1) Log into Windows (local login or VPN) 2) Click on the Windows Start Menu 3) Click on My Computer 4) From the Toolbar click on Tools.

5 5) In the Tools menu click on Map Network Drive 6) From the Map Network Drive Dialog box enter in the Folder box a. Enter: \\geondata\srtm b. Make sure Reconnect at Logon is checked

6 c. Click on different user name and enter your UTEP username and password d. Press Finish 7) When the server directory connects, select the SRTM30_PLUS_900M or SRTMv4_90m to obtain your desired data. 8) When done, please disconnect from the network drive: a. Go to My computer b. From the Toolbar click on Tools c. Select Disconnect Network Drive d. Select the \\geondata\srtm to disconnect and press OK.

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