[Gdal-dev] Problem with Lambert Conformal Conic projection.

[Julien Demaria]

> > When I use gdal_translate with a Lambert Conformal Conic projection,
> > ProjFalseEastingGeokey and ProjFalseNorthingGeokey are not copied.
>
>I tried your example with GDAL CVS and the false easting and northing
>were not lost.  Are you using 1.2.6?  On what platform?  I don't
>*recall* fixing something like this recently, but I have a terrible memory
>so it is possible it was fixed since 1.2.6 was released.

Frank,

I've found this bug 
http://xserve.flids.com/pipermail/gdal-dev/2005-February/008116.html which 
seems to be related since I've made my test with an older gdalinfo.
I've tried with GDAL 1.2.6, it seems work, but I've some questions :

LISTGEO INITIAL FILE :
==============================
...
       GeogGeodeticDatumGeoKey (Short,1): User-Defined
       GeogPrimeMeridianGeoKey (Short,1): PM_Greenwich
       GeogLinearUnitsGeoKey (Short,1): Linear_Meter
       GeogAngularUnitsGeoKey (Short,1): Angular_Degree
       GeogEllipsoidGeoKey (Short,1): Ellipse_GRS_1980
       ProjectedCSTypeGeoKey (Short,1): User-Defined
       ProjectionGeoKey (Short,1): User-Defined
       ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
       ProjLinearUnitsGeoKey (Short,1): Linear_Meter
       ProjStdParallel1GeoKey (Double,1): 44
       ProjStdParallel2GeoKey (Double,1): 49
       ProjNatOriginLongGeoKey (Double,1): 3
       ProjNatOriginLatGeoKey (Double,1): 46.5
       ProjFalseEastingGeoKey (Double,1): 700000
       ProjFalseNorthingGeoKey (Double,1): 6600000
       End_Of_Keys.
    End_Of_Geotiff.

Projection Method: CT_LambertConfConic_2SP
    ProjFalseOriginLatGeoKey: 46.500000 ( 46d30' 0.00"N)
    ProjFalseOriginLongGeoKey: 3.000000 (  3d 0' 0.00"E)
    ProjStdParallel1GeoKey: 44.000000 ( 44d 0' 0.00"N)
    ProjStdParallel2GeoKey: 49.000000 ( 49d 0' 0.00"N)
    ProjFalseEastingGeoKey: 700000.000000 m
    ProjFalseNorthingGeoKey: 6600000.000000 m
==============================

LISTGEO AFTER GDAL_TRANSLATE :
==============================
       GeogGeodeticDatumGeoKey (Short,1): User-Defined
       GeogAngularUnitsGeoKey (Short,1): Angular_Degree
       GeogEllipsoidGeoKey (Short,1): Ellipse_GRS_1980
       ProjectedCSTypeGeoKey (Short,1): User-Defined
       ProjectionGeoKey (Short,1): User-Defined
       ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
       ProjLinearUnitsGeoKey (Short,1): Linear_Meter
       ProjStdParallel1GeoKey (Double,1): 44
       ProjStdParallel2GeoKey (Double,1): 49
       ProjFalseOriginLongGeoKey (Double,1): 3
       ProjFalseOriginLatGeoKey (Double,1): 46.5
       ProjFalseOriginEastingGeoKey (Double,1): 700000
       ProjFalseOriginNorthingGeoKey (Double,1): 6600000
       End_Of_Keys.
    End_Of_Geotiff.

Projection Method: CT_LambertConfConic_2SP
    ProjFalseOriginLatGeoKey: 46.500000 ( 46d30' 0.00"N)
    ProjFalseOriginLongGeoKey: 3.000000 (  3d 0' 0.00"E)
    ProjStdParallel1GeoKey: 44.000000 ( 44d 0' 0.00"N)
    ProjStdParallel2GeoKey: 49.000000 ( 49d 0' 0.00"N)
    ProjFalseEastingGeoKey: 0.000000 m
    ProjFalseNorthingGeoKey: 0.000000 m
==============================

DIFF :
==============================
23,24d20
<       GeogPrimeMeridianGeoKey (Short,1): PM_Greenwich
<       GeogLinearUnitsGeoKey (Short,1): Linear_Meter
33,36c29,32
<       ProjNatOriginLongGeoKey (Double,1): 3
<       ProjNatOriginLatGeoKey (Double,1): 46.5
<       ProjFalseEastingGeoKey (Double,1): 700000
<       ProjFalseNorthingGeoKey (Double,1): 6600000
---
 >       ProjFalseOriginLongGeoKey (Double,1): 3
 >       ProjFalseOriginLatGeoKey (Double,1): 46.5
 >       ProjFalseOriginEastingGeoKey (Double,1): 700000
 >       ProjFalseOriginNorthingGeoKey (Double,1): 6600000
45,46c41,42
<    ProjFalseEastingGeoKey: 700000.000000 m
<    ProjFalseNorthingGeoKey: 6600000.000000 m
---
 >    ProjFalseEastingGeoKey: 0.000000 m
 >    ProjFalseNorthingGeoKey: 0.000000 m
48d43
< Prime Meridian: 8901/Greenwich (0.000000/  0d 0' 0.00"E)
==============================


Some GeoTIFF Tags are modified : why GDAL use :
 >       ProjFalseOriginLongGeoKey (Double,1): 3
 >       ProjFalseOriginLatGeoKey (Double,1): 46.5
 >       ProjFalseOriginEastingGeoKey (Double,1): 700000
 >       ProjFalseOriginNorthingGeoKey (Double,1): 6600000
instead
<       ProjNatOriginLongGeoKey (Double,1): 3
<       ProjNatOriginLatGeoKey (Double,1): 46.5
<       ProjFalseEastingGeoKey (Double,1): 700000
<       ProjFalseNorthingGeoKey (Double,1): 6600000
?

I see in the GeoTIFF specifications that ProjFalseOriginEastingGeoKey is 
different than ProjFalseEastingGeoKey :
"Gives the easting coordinate of the false origin. This is NOT the False 
Easting, which is the easting attached to the Natural origin."
so this isn't coherent ?

In the Lambert Conic Conformal (2SP) specifications 
(http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_2sp.html) 
I understand I should use the ProjFalseOriginXXX keys, but in the GeoTIFF 
web site example for this projection 
(http://www.remotesensing.org/geotiff/spec/geotiff3.html#3.1.3.) the other 
keys are used.....

Many thanks in advance for help,
Best Regards,


Julien