100 0.0 0.0 -100 388900 -331400 file title : DEM Star Mountains, Central New Guinea, UTM combined with shaded image data type : integer file type : binary columns : 2223 rows : 4424 ref. system : utm-54s ref. units : m unit dist. : 1 min. X : 388900 max. X : 611200 min. Y : -773800 max. Y : -331400 pos'n error : unknown resolution : 100 min. value : -9 max. value : 4726 value units : m above sealevel value error : unknown flag value : none flag def'n : none legend cats : 0 derived from raw data of the Shuttle Radar Topography Mission (SRTM)by the author. 8 scenes were downloaded from NASA's srtm ftp site. These were imported to Idrisi (version 2 for windows). Raw data contain "spikes and wells", especially on large surface water areas and wetlands, and at cliffs in mountain areas, like the "Hindenburg Wall" on New Guinea. These gaps were identified as an Idrisi image, buffered by a ring of pixels containing true elevation values. From the buffer-pixels, the void areas were filled by Thiessen-polygons (also named Voronoi Tesselation), and the result pasted on the original image to replace improbable values. Still, this proceedure does not yield real elevation data, but with respect to the inaccuracies of the radar method, and keeping in mind the precautions mentioned below, it is the best Digital Elevation Model available to the public on such a resolution and covering such a large area. The combined jpeg-image from the primary dem and the derived hillshade is to be used for display only. The real data are in demstarm.img. The Star Mountains on New Guinea were chosen, because I am involved in the struggle about the Ok Tedi Copper Mine, located in the Ok Tedi river valley, south of the main divide. See http://www.rettet-die-elbe.de/oktedi/index.html. Klaus Baumgardt Reinbek, Germany, June 2004 Information provided by NASA: SRTM_Topo (last update 11/05/03) SRTM Documentation (best viewed with mono-spaced font, such as courier) 1.0 Introduction The SRTM data sets result from a collaborative effort by the National Aeronautics and Space Administration (NASA) and the National Imagery and Mapping Agency (NIMA), as well as the participation of the German and Italian space agencies, to generate a near-global digital elevation model (DEM) of the Earth using radar interferometry. The SRTM instrument consisted of the Spaceborne Imaging Radar-C (SIR-C) hardware set modified with a Space Station-derived mast and additional antennae to form an interferometer with a 60 meter long baseline. A description of the SRTM mission, can be found in Farr and Kobrick (2000). Synthetic aperture radars are side-looking instruments and acquire data along continuous swaths. The SRTM swaths extended from about 30 degrees off-nadir to about 58 degrees off-nadir from an altitude of 233 km, and thus were about 225 km wide. During the data flight the instrument was operated at all times the orbiter was over land and about 1000 individual swaths were acquired over the ten days of mapping operations. Length of the acquired swaths range from a few hundred to several thousand km. Each individual data acquisition is referred to as a "data take." ReadMeFirst The Shuttle Radar Topography Mission (SRTM) data products result from a collaborative mission by the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA), the German space agency (DLR) and Italian space agency (ASI), to generate a near-global digital elevation model (DEM) of the Earth using radar interferometry. The SRTM-1 (1 arc-second) and SRTM-3 (3 arc-second) digital elevation models are being developed from the SRTM C-band radar observations for selected regions to satisfy the needs of NASA related projects and to speed the evaluation of acquisition and processing and applications algorithms. The SRTM-1 and SRTM-3 are preliminary terrain height data sets. NASA has taken significant efforts to avoid confusion of the SRTM-1 and SRTM-3 digital elevation models with the NIMA standard (Digital Terrain Elevation Data) DTED-1 and DTED-2 terrain height data sets. The SRTM-1 and SRTM-3 data products result from special processing of the SRTM data in response to requests from Principal Investigators selected under NASA's Solid Earth and Natural Hazards Program, as well as other special requests from NIMA and NASA. The SRTM-1 and SRTM-3 data are preliminary products distributed for evaluation by the research and applications user community. A further description of the data may be found in the document SRTM_Topo.doc. ********************************************************************************* The SRTM-1 and SRTM-3 are preliminary data products, contain numerous artifacts, and are not intended for use in navigation or other critical, operations-related applications. ********************************************************************************* The SRTM-1 and SRTM-3 data differ from DTED in a number of ways: 1. They are unedited, and may contain numerous voids (regions with no data) and other spurious point such as anomalously high ("spike") or low ("well") values. 2. Coastlines of water bodies are typically not well delineated and may not appear "flat". 3. They have not been evaluated for conformance with National Mapping Accuracy standards. 4. SRTM-1 and SRTM-3 differ significantly in data format from the DTED standards. NASA and NIMA welcome comments as well as the results of any evaluations or analysis of these data. Please direct any comments or communications to Mike Kobrick at mkobrick@jpl.nasa.gov or Tom Farr at tom.farr@jpl.nasa.gov.