<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta content="text/html;charset=UTF-8" http-equiv="Content-Type"></head><body ><div style='font-size:10pt;font-family:Verdana,Arial,Helvetica,sans-serif;'><div>Hi Even,</div><div>Thanks for the reply.</div><div><br></div><div>I guess GDAL chose Mercator_1SP because that's the one that's explicitly defined in the projection text.</div><div><br></div><div>I've had a quick look at the two files using listgeo, and highlighted the different lines with **** prefix below (it seems GDAL removes 6 tags, and adds one).</div><div><br></div><div>The before:</div><div><i> Keyed_Information:</i></div><div><i> GTModelTypeGeoKey (Short,1): ModelTypeProjected</i></div><div><i> GTRasterTypeGeoKey (Short,1): RasterPixelIsArea</i></div><div><i> GTCitationGeoKey (Ascii,9): "Mercator"</i></div><div><i> GeographicTypeGeoKey (Short,1): GCS_WGS_84</i></div><div><i> GeogCitationGeoKey (Ascii,7): "WGS 84"</i></div><div><i> ****GeogGeodeticDatumGeoKey (Short,1): Datum_WGS84</i></div><div><i> ****GeogLinearUnitsGeoKey (Short,1): Linear_Meter </i></div><div><i> GeogAngularUnitsGeoKey (Short,1): Angular_Degree</i></div><div><i> ****GeogEllipsoidGeoKey (Short,1): Ellipse_WGS_84</i></div><div><i> GeogSemiMajorAxisGeoKey (Double,1): 6378137</i></div><div><i> ****GeogSemiMinorAxisGeoKey (Double,1): 6356752.31424518</i></div><div><i> GeogInvFlatteningGeoKey (Double,1): 298.257223563</i></div><div><i> ProjectedCSTypeGeoKey (Short,1): User-Defined</i></div><div><i> ****PCSCitationGeoKey (Ascii,9): "Mercator"</i></div><div><i> ProjectionGeoKey (Short,1): User-Defined</i></div><div><i> ProjCoordTransGeoKey (Short,1): CT_Mercator</i></div><div><i> ProjLinearUnitsGeoKey (Short,1): Linear_Meter</i></div><div><i> ****ProjStdParallel1GeoKey (Double,1): 60</i></div><div><i> ProjNatOriginLongGeoKey (Double,1): 0</i></div><div><i> ProjNatOriginLatGeoKey (Double,1): 0</i></div><div><i> ProjFalseEastingGeoKey (Double,1): 0</i></div><div><i> ProjFalseNorthingGeoKey (Double,1): 0</i></div><div><i> End_Of_Keys.</i></div><div><span class="Apple-tab-span" style="white-space:pre"> </span> </div><div>------------</div><div>The after:</div><div><i> Keyed_Information:</i></div><div><i> GTModelTypeGeoKey (Short,1): ModelTypeProjected</i></div><div><i> GTRasterTypeGeoKey (Short,1): RasterPixelIsArea</i></div><div><i> GTCitationGeoKey (Ascii,9): "Mercator"</i></div><div><i> GeographicTypeGeoKey (Short,1): GCS_WGS_84</i></div><div><i> GeogCitationGeoKey (Ascii,7): "WGS 84"</i></div><div><i> GeogAngularUnitsGeoKey (Short,1): Angular_Degree</i></div><div><i> GeogSemiMajorAxisGeoKey (Double,1): 6378137</i></div><div><i> GeogInvFlatteningGeoKey (Double,1): 298.257223563</i></div><div><i> ProjectedCSTypeGeoKey (Short,1): User-Defined</i></div><div><i> ProjectionGeoKey (Short,1): User-Defined</i></div><div><i> ProjCoordTransGeoKey (Short,1): CT_Mercator</i></div><div><i> ProjLinearUnitsGeoKey (Short,1): Linear_Meter</i></div><div><i> ProjNatOriginLongGeoKey (Double,1): 0</i></div><div><i> ProjNatOriginLatGeoKey (Double,1): 0</i></div><div><i> ProjFalseEastingGeoKey (Double,1): 0</i></div><div><i> ProjFalseNorthingGeoKey (Double,1): 0</i></div><div><i> ****ProjScaleAtNatOriginGeoKey (Double,1): 1</i></div><div><i> End_Of_Keys.</i></div><div><i> End_Of_Geotiff.</i></div><div> </div><div><br></div><div>I'm not clear on why the things that changed were changed, but I can see that GDAL removed the <b>ProjStdParallel1GeoKey</b> and value. Should not that have been displayed by GDALSRSInfo for the Before file, even if it was wrongly set for this given projection?</div><div><br></div><div>Thanks,</div><div>Jonathan</div><div><br><div class="zmail_extra"><div id="1"><br>---- On Tue, 17 Nov 2015 09:18:49 -0800 <b>Even Rouault<even.rouault@spatialys.com></b> wrote ---- <br></div><blockquote style="border-left: 1px solid #0000FF; padding-left: 6px; margin:0 0 0 5px">Le mardi 17 novembre 2015 17:55:15, Jonathan Moules a écrit : <br>> Hi List, <br>> I have a Geotiff which includes this projection: <br>> <br>> PROJ.4 : '+proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m <br>> +no_defs ' <br>> <br>> <br>> OGC WKT : <br>> PROJCS["Mercator", <br>> GEOGCS["WGS 84", <br>> DATUM["WGS_1984", <br>> SPHEROID["WGS 84",6378137,298.257223563, <br>> AUTHORITY["EPSG","7030"]], <br>> AUTHORITY["EPSG","6326"]], <br>> PRIMEM["Greenwich",0], <br>> UNIT["degree",0.0174532925199433], <br>> AUTHORITY["EPSG","4326"]], <br>> PROJECTION["Mercator_1SP"], <br>> PARAMETER["central_meridian",0], <br>> PARAMETER["scale_factor",1], <br>> PARAMETER["false_easting",0], <br>> PARAMETER["false_northing",0], <br>> UNIT["metre",1, <br>> AUTHORITY["EPSG","9001"]]] <br>> <br>> <br>> <br>> <br>> If I load this raster into ArcGIS, it displays in the wrong place (a few <br>> thousand kilometres North). <br>> <br>> <br>> I then run it through gdal_translate (GDAL 1.11.1), with no flags: <br>> * gdal_trainslate input.tif output.tif <br>> <br>> For output.tif, GDALSRSInfo shows that the projection is identical, but now <br>> the file loads correctly in ArcGIS. The same file works fine in QGIS both <br>> before and after the "translation". <br>> <br>> <br>> Looking at the projection info in ArcGIS, it displays one difference: <br>> Before (not working): <br>> Standard_parallel_1 = 60 <br>> <br>> <br>> After (working): <br>> Standard_parallel_1 = 0 <br>> <br>> <br>> But I don't see anything about those in either of the GDALSRSInfo outputs. <br>> <br>> <br>> So my questions: <br>> - What is gdal_translate doing to the file to "fix" it? <br>> - If it is something to do with Standard Parallel 1 - why isn't this <br>> component of the projection exposed by GDAL? <br> <br>Yes, in Mercator_1SP, there's no Standard Parallel 1, this is for <br>Mercator_2SP. <br> <br>See <br><a href="http://www.remotesensing.org/geotiff/proj_list/mercator_1sp.html" target="_blank">http://www.remotesensing.org/geotiff/proj_list/mercator_1sp.html</a> <br><a href="http://www.remotesensing.org/geotiff/proj_list/mercator_2sp.html" target="_blank">http://www.remotesensing.org/geotiff/proj_list/mercator_2sp.html</a> <br> <br>I guess your original geotiff file has some unusual formulation which is <br>detected as Mercator_1SP by GDAL, and probably Mercator_2SP by ArCGIS. <br> <br>You could try with the listgeo utility that comes with libgeotiff to display <br>the geotiff keys. <br> <br>> <br>> Thoughts welcome. <br>> Thanks, <br>> Jonathan <br> <br>-- <br>Spatialys - Geospatial professional services <br><a href="http://www.spatialys.com" target="_blank">http://www.spatialys.com</a> <br></blockquote><br></div><br></div></div></body></html>