Hi,

Willem43, the projection of your geotiff is wrong, for use with M you need to have lat / lon.

Header from gdalinfo should look like this :

Size is 6147, 3881
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.2572235630016,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Origin = (3.161506588568127,51.273576981769018)
Pixel Size = (0.000076314465007,-0.000048559462332)
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
COMPRESSION=LZW
INTERLEAVE=BAND


We use this projection, because it use less cpu to render a map position.

Fabrice