[Geotiff] Encoding of "ETRS89 / ETRS-LAEA" (i.e. EPSG:3035)

[Frank Warmerdam]

Pierre Soille wrote:
> 
> The problem we face is how to encode the "ETRS89 / ETRS-LAEA"
> (i.e. EPSG:3035) projection 'correctly' into GeoTiff Keys (see
> http://www.ec-gis.org/sdi/publist/pdfs/annoni-etal2003eur.pdf for the
> definition of this projection).
> 
>  From http://www.remotesensing.org/geotiff/spec/geotiff6.html#6.3.3.1
> we could not find any ProjectedCSTypeGeoKey code for this projection.
> Therefore, one is forced to user-define all relevant parameters. 

Pierre,

It is common practice to use PCS and GCS codes that have been added to
EPSG even though they do not appear in the GeoTIFF specification.  So
my primary advice is to just use 3035 as the PCS and leave it at that.

There is some danger in doing this for very recent codes, in that older
software packages (or new packages without an EPSG update) won't recognise
the coordinate system.  But I see that 3035 has been around since at least
EPSG 6.13.


> In any case, we would also be grateful for feedback on the purpose and
> proper use of the 'GTCitationGeoKey' and the 'PCSCitationGeoKey' which
> often are used quite arbitrarily.

These citations are pretty arbitrary.

> GeograpicTypeGeoKey
> 
> 4258
> 
> EPSG parameter COORD_REF_SYS_CODE for COORD_REF_SYS_NAME 'ETRS89', GeoTIFF
> label is 'GCS_EUREF89'
...
> GeogGeodeticDatumGeoKey
> 
> 6258
> 
> EPSG DATUM_CODE for  DATUM_NAME 'European Terrestrial Reference System
> 1989', GeoTIFF label is 'Datum_European_Reference_System_1989'"

Note that datum, prime meridian, etc are all implicit in the
GeographicTypeGeoKey value of 4258.  There is no harm in explicitly
defining them, but in theory it is not necessary.

...

> ProjCoordTransGeoKey          
> 10
> 
> GeoTIFF code for label: 'CT_LambertAzimEqualArea'
> 
> 
> 
> ProjLinearUnitsGeoKey
> 
> 9001
> 
> EPSG uom_code for 'meter' (ISO 1000)
> 
> 
> 
> ProjFalseEastingGeoKey
> 
> 4321000.0d
> 
> in Projection System Linear Units (Key 3076)
> 
> 
> 
> ProjFalseNorthingGeoKey
> 
> 3210000.0d
> 
> in Projection System Linear Units (Key 3076)
> 
>  
> ProjCenterLongGeoKey
> 
> 10.000000d
> 
> in Geographic System Angular Units (Key 2054)
> 
> 
> 
> ProjCenterLatGeoKey      
> 52.000000d
> 
> in Geographic System Angular Units (Key 2054)

These all look fine to me.

Just be aware that there is a wide variety of geotiff readers in this
world, with greater and lesser degrees of implementation sophistication.
I suspect you are running into some less sophisticated readers.  If you
want your formulation reviewed more exactly you might want to provide
a small sample file, with what you believe the corners ought to be if
reprojected into the geographic coordinate system.  Then I could try my
software on it, and more exactly see how you have written the file.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org