From even.rouault at spatialys.com Wed Apr 15 11:15:45 2015 From: even.rouault at spatialys.com (Even Rouault) Date: Wed, 15 Apr 2015 18:15:45 +0200 Subject: [Geotiff] Encoding EPSG:3857 (WebMercator) in GeoTIFF, and ArcGIS interoperability Message-ID: <201504151815.45808.even.rouault@spatialys.com> Hi, I've collected in http://trac.osgeo.org/gdal/ticket/5924 a summary of issues and findings when trying to write GeoTIFF files in EPSG:3857 in a "standard" way (using ProjectedCSTypeGeoKey = 3857), while making them correctly displayed by ArcGIS (and ideally by other independant implementations). The current situation is that there's no such way (AFAIK). I'd appreciate any feedback/suggestion related to that issue. Best regards, Even -- Spatialys - Geospatial professional services http://www.spatialys.com From lhomme.xavier at gmail.com Wed Apr 15 11:21:51 2015 From: lhomme.xavier at gmail.com (xavier lhomme) Date: Wed, 15 Apr 2015 18:21:51 +0200 Subject: [Geotiff] [gdal-dev] Encoding EPSG:3857 (WebMercator) in GeoTIFF, and ArcGIS interoperability In-Reply-To: <201504151815.45808.even.rouault@spatialys.com> References: <201504151815.45808.even.rouault@spatialys.com> Message-ID: Dis you try with 102113 or 102100 instead of 3857 ? I had once to use those code in order to be discovered as 3857 in arcgis. when i created geotiff with gdal warp/transform. Le 15 avr. 2015 18:16, "Even Rouault" a ?crit : > Hi, > > I've collected in http://trac.osgeo.org/gdal/ticket/5924 a summary of > issues > and findings when trying to write GeoTIFF files in EPSG:3857 in a > "standard" way > (using ProjectedCSTypeGeoKey = 3857), while making them correctly > displayed by > ArcGIS (and ideally by other independant implementations). > The current situation is that there's no such way (AFAIK). I'd appreciate > any > feedback/suggestion related to that issue. > > Best regards, > > Even > > -- > Spatialys - Geospatial professional services > http://www.spatialys.com > _______________________________________________ > gdal-dev mailing list > gdal-dev at lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.maptools.org/pipermail/geotiff/attachments/20150415/4e98ae82/attachment.htm From even.rouault at spatialys.com Wed Apr 15 12:59:36 2015 From: even.rouault at spatialys.com (Even Rouault) Date: Wed, 15 Apr 2015 19:59:36 +0200 Subject: [Geotiff] [gdal-dev] Encoding EPSG:3857 (WebMercator) in GeoTIFF, and ArcGIS interoperability In-Reply-To: References: <201504151815.45808.even.rouault@spatialys.com> Message-ID: <201504151959.36977.even.rouault@spatialys.com> Le mercredi 15 avril 2015 18:21:51, xavier lhomme a ?crit : > Dis you try with 102113 or 102100 instead of 3857 ? I had once to use > those code in order to be discovered as 3857 in arcgis. when i created > geotiff with gdal warp/transform. Xavier, thanks for the hint. I've just tried it and thinks it qualifies as yet another not completely satisfactory solution. Using -a_srs EPSG:102113 effectively results in a correctly placed geotiff in ArcGIS (with a warning about it being in GCS_WGS_1984_Major_Auxiliary_Sphere), but there are several points that are not that great : - this is not a standard EPSG code - due to being > 32767, it is not encoded in ProjectedCSTypeGeoKey, which was one of my "requirement" - when read by GDAL, the expanded GeoTIFF definition isn't properly identified as WebMercator, consequently the proj.4 string lacks the "+nadgrids=@null" stuff, which makes it a non-complete datum definition and cause issues when reprojecting such GeoTIFF with GDAL (lack of datum transformation from/to the WGS84 datum of WebMercator). That could admitedly being tweaked in GDAL. For the record, the GeoTIFF keys written by GDAL are: {{{ GTModelTypeGeoKey (Short,1): ModelTypeProjected GTRasterTypeGeoKey (Short,1): RasterPixelIsArea GTCitationGeoKey (Ascii,22): "WGS_1984_Web_Mercator" GeographicTypeGeoKey (Short,1): User-Defined GeogCitationGeoKey (Ascii,151): "GCS Name = GCS_WGS_1984_Major_Auxiliary_Sphere|Datum = WGS_1984_Major_Auxiliary_Sphere| Ellipsoid = WGS_1984_Major_Auxiliary_Sphere|Primem = Greenwich|" GeogGeodeticDatumGeoKey (Short,1): User-Defined GeogAngularUnitsGeoKey (Short,1): Angular_Degree GeogEllipsoidGeoKey (Short,1): User-Defined GeogSemiMajorAxisGeoKey (Double,1): 6378137 GeogSemiMinorAxisGeoKey (Double,1): 6378137 GeogPrimeMeridianLongGeoKey (Double,1): 0 ProjectedCSTypeGeoKey (Short,1): User-Defined ProjectionGeoKey (Short,1): User-Defined ProjCoordTransGeoKey (Short,1): CT_Mercator ProjLinearUnitsGeoKey (Short,1): Linear_Meter ProjNatOriginLongGeoKey (Double,1): 0 ProjNatOriginLatGeoKey (Double,1): 0 ProjFalseEastingGeoKey (Double,1): 0 ProjFalseNorthingGeoKey (Double,1): 0 ProjScaleAtNatOriginGeoKey (Double,1): 1 }}} And GDAL reads that as : {{{ PROJCS["WGS_1984_Web_Mercator", GEOGCS["GCS_WGS_1984_Major_Auxiliary_Sphere", DATUM["WGS_1984_Major_Auxiliary_Sphere", SPHEROID["WGS_1984_Major_Auxiliary_Sphere",6378137,0]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433]], PROJECTION["Mercator_1SP"], PARAMETER["central_meridian",0], PARAMETER["scale_factor",1], PARAMETER["false_easting",0], PARAMETER["false_northing",0], UNIT["metre",1, AUTHORITY["EPSG","9001"]]] }}} (not sure why it lacks the latitude_of_origin, but that's another minor issue) ArcCatalog identifies the SRS as: {{{ WGS_1984_Web_Mercator WKID: 3785 Authority: EPSG Projection: Mercator false_easting: 0.0 false_northing: 0.0 central_meridian: 0.0 standard_parallel_1: 0.0 Linear Unit: Meter (1.0) Geographic Coordinate System: GCS_WGS_1984_Major_Auxiliary_Sphere Angular Unit: Degree (0.0174532925199433) Prime Meridian: Greenwich (0.0) Datum: D_WGS_1984_Major_Auxiliary_Sphere Spheroid: WGS_1984_Major_Auxiliary_Sphere Semimajor Axis: 6378137.0 Semiminor Axis: 6378137.0 Inverse Flattening: 0.0 }}} Even > > Le 15 avr. 2015 18:16, "Even Rouault" a ?crit : > > Hi, > > > > I've collected in http://trac.osgeo.org/gdal/ticket/5924 a summary of > > issues > > and findings when trying to write GeoTIFF files in EPSG:3857 in a > > "standard" way > > (using ProjectedCSTypeGeoKey = 3857), while making them correctly > > displayed by > > ArcGIS (and ideally by other independant implementations). > > The current situation is that there's no such way (AFAIK). I'd appreciate > > any > > feedback/suggestion related to that issue. > > > > Best regards, > > > > Even > > > > -- > > Spatialys - Geospatial professional services > > http://www.spatialys.com > > _______________________________________________ > > gdal-dev mailing list > > gdal-dev at lists.osgeo.org > > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Spatialys - Geospatial professional services http://www.spatialys.com