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Accuracy issue reprojecting between EPSG:27572 and EPSG:2154

Description

From email:

Situation :

  • Geoserver 2.12.3 (olders have been tested too with same observations)

  • A first layer is created to load a shape projected in 27572

  • A second one is created to load a raster projected in 2154

  • An agregation is created to mix these two layers, projected in 27572.


Problem :

  • The shape is not well placed on the raster, not very far but not good.

If I compare the definition of the projection and the projection on https://epsg.io/, I can see that there is some differences (parameters TOWGS84 is missing, some values are differents…).
I can then use epsg_overrides.properties to define the projection given in epsg.io.
Unfortunately, the result is worst.

After further try, I mixed the native parameters of 27572 known in GeoServer and official parameters given on epsg.io and obtain something good :

1 27572=PROJCS["NTF (Paris) / Lambert zone II",GEOGCS["NTF (Paris)",DATUM["Nouvelle_Triangulation_Francaise_Paris",SPHEROID["Clarke 1880 (IGN)",6378249.2,293.4660212936269,AUTHORITY["EPSG","7011"]],TOWGS84[-168,-60,320,0,0,0,0],AUTHORITY["EPSG","6807"]],PRIMEM["Paris", 2.5969213, AUTHORITY["EPSG","8903"]],UNIT["grade",0.015707963267948967],AXIS["Geodetic longitude", EAST],AXIS["Geodetic latitude", NORTH],AUTHORITY["EPSG","4807"]],PROJECTION["Lambert_Conformal_Conic_1SP", AUTHORITY["EPSG","9801"]],PARAMETER["central_meridian", 0.0],PARAMETER["latitude_of_origin", 52.0],PARAMETER["scale_factor", 0.99987742],PARAMETER["false_easting", 600000.0],PARAMETER["false_northing", 2200000.0],UNIT["m", 1.0],AXIS["Easting", EAST],AXIS["Northing", NORTH],AUTHORITY["EPSG","27572"]]

I hope it could help.

Clément

Environment

None

Status

Assignee

Unassigned

Reporter

Jody Garnett

Triage

None

Components

Affects versions

18.2

Priority

Medium