<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Dear Sir/Madame,<div><br></div><div>I have recently downloaded a number of historic analogue maps which have associated .twf and .tab files. I notice that both these text files are required by GDAL for geo-referencing according to the information given on the appropriate web page for inputing tiff/geotiff files.</div><div><br></div><div>In this particular case the two files are not compatible with each telling the system slightly different things. I have copied the contents below. How will GDAL handle this situation?</div><div><br></div><div>Thanks</div><div><br></div><div>Tim Southern</div><div><br></div><div>.tab file</div><div><br></div><div><div><div><font color="#0056d6">!table</font></div><div><font color="#0056d6">!version 300</font></div><div><font color="#0056d6">!charset WindowsLatin1</font></div><div><font color="#0056d6"><br></font></div><div><font color="#0056d6">Definition Table</font></div><div><font color="#0056d6"> File "02SU5980.tif"</font></div><div><font color="#0056d6"> Type "RASTER"</font></div><div><font color="#0056d6"> (459000, 181001) (0,0) Label "Pt 1",</font></div><div><font color="#0056d6"> (459999, 181001) (4723,0) Label "Pt 2",</font></div><div><font color="#0056d6"> (459999, 180001) (4723,4723) Label "Pt 3",</font></div><div><font color="#0056d6"> (459000,180001) (0,4723) Label "Pt 4"</font></div><div><font color="#0056d6"> CoordSys Earth Projection 8, 79, "m", -2, 49, 0.9996012717, 400000, -100000</font></div></div><div><br></div><div><br></div><div>and the .twf file is</div><div><br></div><div><font color="#0042aa">0.21168000</font></div><div><font color="#0042aa">0.0000</font></div><div><font color="#0042aa">0.0000</font></div><div><font color="#0042aa">-0.21168000</font></div><div><font color="#0042aa">459000.00000000</font></div><div><font color="#0042aa">181000.00000000</font></div><div><div><br class="webkit-block-placeholder"></div><div>The .tab file gives coordinates for the pixel 0, 0 as <font color="#e63b7a">459000, 181001</font> whereas the .twf file defines the same pixel as <font color="#e63b7a">459000, 181000</font>.</div><div>The .tab file gives coordinates for the pixel 4723,0 as <font color="#e63b7a">459999, 181001</font> whereas the .twf gives the same pixels as <font color="#e63b7a">459999.76464, 181000</font>.</div><div>The .tab file gives coordinates for the pixel 4723, 4723 as <font color="#e63b7a">459999, 180001</font> whereas .twf file gives same point as <font color="#e63b7a">459999.76464, 180000.23536</font></div><div>The .tab file gives coordinates for the pixel 0, 4723 as <font color="#e63b7a">459000, 180001</font> whereas .twf file gives same point as <font color="#e63b7a">459000, 180000.23536</font></div><div><br></div><div>Another obvious difference is .tab file define a rectangle <font color="#e63b7a">999 by 1000</font> metres whereas the .twf file defines a square <font color="#e63b7a">999.76464 by 999.76464</font> metres.</div></div></div><div><br></div><br><br><div>
<div>Tim Southern</div><div>17, Park Close,</div><div>Sonning Common,</div><div>Oxfordshire</div><div>RG4 9RY</div><div><br></div><br class="Apple-interchange-newline">
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