fix(geotiff): read projection origin from all equivalent GeoKeys

[kylebarron]

the GeoKey parsing to PROJJSON is already vibe coded, so we continue to let claude vibe code it with more and more test files

This should hopefully fix source-cooperative/cog-viewer#40

Validated in the dev app that it's now rendering in the right place:

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Note

Written by Claude (Claude Code) on behalf of @kylebarron, not by @kylebarron.

Fixes source-cooperative/cog-viewer#40

Bug

O2308000_7586000_cog.tif uses New Brunswick Stereographic (equivalent to EPSG:2953), stored as a user-defined CRS with ProjCoordTransGeoKey = CT_ObliqueStereographic. GDAL wrote the origin into ProjNatOriginLatGeoKey / ProjNatOriginLongGeoKey / ProjScaleAtNatOriginGeoKey, but crsFromGeoKeys read ProjCenter* / ProjScaleAtCenter for this method. Those keys were missing, so the origin fell back to (0, 0) with scale 1, and the image rendered near Null Island.

Fix

Each projection method read its origin, scale factor and false easting/northing from a single hand-picked key. libgeotiff instead takes each one from the first of several equivalent keys that is present:

Parameter	Keys, in order
Origin latitude	ProjNatOriginLat → ProjFalseOriginLat → ProjCenterLat
Origin longitude	ProjNatOriginLong → ProjFalseOriginLong → ProjCenterLong
Scale factor	ProjScaleAtNatOrigin → ProjScaleAtCenter
False easting	ProjFalseEasting → ProjCenterEasting → ProjFalseOriginEasting
False northing	ProjFalseNorthing → ProjCenterNorthing → ProjFalseOriginNorthing

_buildConversion now does the same for every method. When the key a method used to read is present, it still gets the same value. Albers and LCC 2SP keep checking their false-origin keys first.

This also fixes Stereographic: GDAL writes its scale factor to ProjScaleAtNatOrigin, which we didn't read, so it was always 1.

Tests

• The Oblique Stereographic fixture from feat: Add user-defined Oblique Stereographic CRS fixture geotiff-test-data#71 (the submodule bump also brings in upstream fixture PRs chore: Rename existing COGLayer to GeoTIFFLayer #59–Allow passing on some TileLayer props to COGLayer #70) now gives the expected conversion parameters.
• The same GeoKeys, arranged the way GDAL writes Stereographic, give the right scale factor.
• Checked by hand: the fixture's top-left corner maps to (-69.0373387°, 47.2637446°) through parseWkt and proj4. pyproj gives the same point (EPSG:2953 → EPSG:4617) to within 2e-11°.

Not fixed here

• Hotine Oblique Mercator: GDAL treats CT_ObliqueMercator (3) as variant A, but we emit variant B. We also take the "Angle from Rectified to Skew Grid" from ProjAzimuthAngleGeoKey rather than ProjRectifiedGridAngleGeoKey.
• When the datum is an EPSG code, we don't pass on the ellipsoid given in the file's GeoKeys, so proj4 uses WGS84's instead.

🤖 Written by Claude Code