Error in data in `ProjectionGeoKey.js`
Closed this issue · 6 comments
My geotiff file has the following (somewhat mysterious) geoKeys:
GTCitationGeoKey: "UTM Zone 32, Northern Hemisphere"
GTModelTypeGeoKey: 1
GTRasterTypeGeoKey: 1
GeogAngularUnitsGeoKey: 9102
GeogCitationGeoKey: "GCS Name = GRS 1980(IUGG, 1980)|Datum = unknown|Ellipsoid = GRS80|Primem = Greenwich|"
GeogEllipsoidGeoKey: 32767
GeogGeodeticDatumGeoKey: 32767
GeogInvFlatteningGeoKey: 298.257222101
GeogPrimeMeridianLongGeoKey: 0
GeogSemiMajorAxisGeoKey: 6378137
GeogTOWGS84GeoKey: [ 0, 0, 0 ]
GeographicTypeGeoKey: 32767
ProjLinearUnitsGeoKey: 9001
ProjectedCSTypeGeoKey: 32767
ProjectionGeoKey: 16032
which convertGeoKeys2proj4 converts to this string:
+proj=tmerc +lat_0=0 +lon_0=0.1570796326794895 +k_0=0.9996 +x_0=500000 +y_0=0 +a=6378137 +b=6356752.314140356 +towgs84=0,0,0, +no_defs
This is not quite right - the lon_0 value should be 9, as listgeo lists the tiff file as follows:
eotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
554006.599009888 6301417.47768047 0
ModelPixelScaleTag (1,3):
0.356706451650175 0.356706451650175 0
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
GTCitationGeoKey (Ascii,33): "UTM Zone 32, Northern Hemisphere"
GeographicTypeGeoKey (Short,1): User-Defined
GeogCitationGeoKey (Ascii,86): "GCS Name = GRS 1980(IUGG, 1980)|Datum = unknown|Ellipsoid = GRS80|Primem = Greenwich|"
GeogGeodeticDatumGeoKey (Short,1): User-Defined
GeogAngularUnitsGeoKey (Short,1): Angular_Degree
GeogEllipsoidGeoKey (Short,1): User-Defined
GeogSemiMajorAxisGeoKey (Double,1): 6378137
GeogInvFlatteningGeoKey (Double,1): 298.257222101
GeogPrimeMeridianLongGeoKey (Double,1): 0
GeogTOWGS84GeoKey (Double,3): 0 0 0
ProjectedCSTypeGeoKey (Short,1): User-Defined
ProjectionGeoKey (Short,1): Proj_UTM_zone_32N
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
End_Of_Keys.
End_Of_Geotiff.
Projection = 16032 (UTM zone 32N)
Projection Method: CT_TransverseMercator
ProjNatOriginLatGeoKey: 0.000000 ( 0d 0' 0.00"N)
ProjNatOriginLongGeoKey: 9.000000 ( 9d 0' 0.00"E)
ProjScaleAtNatOriginGeoKey: 0.999600
ProjFalseEastingGeoKey: 500000.000000 m
ProjFalseNorthingGeoKey: 0.000000 m
TOWGS84: 0,0,0
Projection Linear Units: 9001/metre (1.000000m)
The problem seems to be in data preparation, because the string for 16032 in ProjectionGeoKey.js has the wrong value. On http://epsg.io/16032.gml, the latitude is 9. The problem seems simply a mixup between degrees and radians: 0.1570796326794895 is 9 degrees in radians.
Hello again, thanks for the report, I really appreciate the effort!
I've got a lot going on lately, so it'll take some time for me to look into this issue, sorry :)
Looks like it's fixed. It passes my tests with geokeys from this issue, but I'm a bit unsure if I've covered everything while refactoring.
If you have a larger dataset, may I ask you to extract geokeys and whatever Proj4 strings GDAL outputs, and send it to me?
The library now returns this proj4 string for my geokeys:
+proj=tmerc +lat_0=0 +lon_0=8.999999999999991 +k_0=0.9996 +x_0=500000 +y_0=0 +a=6378137 +b=6356752.314140356 +towgs84=0,0,0, +no_defs
It turns out that openlayers cannot correctly parse this. The problem is the +towgs84=0,0,0, part. If I change it to +towgs84=0,0,0 (that is, remove the final comma), then it works correctly.
Also, somehow when preparing the data you are changing the 9 degrees in the specification into 8.999999999999991 degrees. It would be nicer if you could round to 12 digits or something like that, so that the degrees would exactly match the specification.
Thanks, fixed it! Also good point regarding the numbers, done the rounding at the end of string processing to not mess up everything.
An updated version should already be in npm :)
Thanks, I can confirm that now it works!
Thanks, been a pleasure working with you!