<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi,<div> I've been doing a bit of reading, so in essence, SRTM data is nothing but raster data, stored using 16-bit signed integer. Depending upon the arc length, you will have either 1201x1201 or 3601x3601 data elements. So, all I have to do is to import each value, taking take to perform byte swapping, since I am using a Mac Book Pro with an Intel processor, and read in two bytes of data, corresponding to a pixel element value, that can later be used to create a raster image of height field data. </div><div><br></div><div>I guess the next step is to create a vtkSRTMReader class for VTK, and construct a vtkImageData object as output, which can then be used to render a height field.<br></div><div><br></div><div>Any help or pointers to some examples would be greatly appreciated, since it will help me build this class quickly. :-) !</div><div><br></div><div>Best regards,</div><div><br></div><div>Elvis Dowson</div><div><br><div><div>On Oct 12, 2008, at 11:36 PM, Elvis Dowson wrote:</div><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><br></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">DEM File (.HGT)</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">The DEM is provided as 16-bit signed integer data in a simple binary raster. There are no header</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">or trailer bytes embedded in the file. The data are stored in row major order (all the data for row</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">1, followed by all the data for row 2, etc.).</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">All elevations are in meters referenced to the WGS84/EGM96 geoid as documented at http://</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; "><a href="http://www.NGA.mil/GandG/wgsegm/">www.NGA.mil/GandG/wgsegm/</a>.</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">Byte order is Motorola ("big-endian") standard with the most significant byte first. Since they are</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">signed integers elevations can range from -32767 to 32767 meters, encompassing the range of</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">elevation to be found on the Earth.</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">These data also contain occassional voids from a number of causes such as shadowing, phase</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Times; ">unwrapping anomalies, or other radar-specific causes. Voids are flagged with the value -32768.</div></div></div></blockquote></div><br></div></body></html>