<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi,<div> Looking at the list of VTK classes, I think that vtkImageReader2 could be used to read the SRTM DEM data file, with byte swapping on. A vtkImageData object is obtained from vtkImageAlgorithm::GetOutput(), which is a superclass of vtkImageReader2. <div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; ">One thing I am not so sure of is what I should do about the following vtkImageReader2 methods</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><a class="el" href="file:///Users/elvis/Tool/vtk-5.x/doc/html/a00665.html#b853fba8decf9550e4678fa4f4ca9ad0" style="color: rgb(26, 65, 168); text-decoration: none; background-color: rgb(242, 242, 255); ">SetDataExtent</a> (int, int, int, int, int, int)</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><a class="el" href="file:///Users/elvis/Tool/vtk-5.x/doc/html/a00665.html#292158a26416f4ad425e93910b9ba168" style="color: rgb(26, 65, 168); text-decoration: none; ">SetDataSpacing</a> (double, double, double)</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><a class="el" href="file:///Users/elvis/Tool/vtk-5.x/doc/html/a00665.html#baf54472672e99b1fb4c078f6b17cd26" style="color: rgb(26, 65, 168); text-decoration: none; background-color: rgb(242, 242, 255); ">SetDataOrigin</a> (double, double, double)</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; ">If the value in SRTM array data position [0][0] = +100, then do I store this at the following coordinate location x=0, y=0, z=+100 ? Is this correct? That is, the first element is stored at the lower left cornet and the z value is interpreted as a scalar value for the height field? Is this how it works when reading DEM files, and what vtkDEMReader does?</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; ">Best regards,</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; ">Elvis Dowson</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; "><br></div><div><div><br></div><blockquote type="cite"><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div>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><br></div></div></blockquote></div></div></body></html>