Geotiff and MrSId - inconsistent georeference

[LeeB]

Hi,

I have created a MrSId file from a GeoTiff file hence the projection and image extents should be identical.

When I decode the GeoTiff, the image extents are:
Projection: UTM
Zone 14N
Top:4000000
Left: 600000
Bottom:3900000
Right:700000

When I decode the equavalent MrSID file I get the following
Projection: UTM
Zone 14N
Top:3999950
Left: 600050
Bottom:3899950
Right:700050

Strangely though, when I view the two files in GeoExpress the image extents displayed are both as per the GoeTiff file.

Perhaps I mssing something but to get the geo extents I'm simply doing to the following...

LTIGeoCoord fileGeoData = sidReader->getGeoCoord();
topLeft.x = fileGeoData.getX();
topLeft.y = fileGeoData.getY();
bottomRight.y = fileGeoData.getY() + (sidReader->getHeight() * fileGeoData.getYRes());
bottomRight.x = fileGeoData.getX() + (sidReader->getWidth() * fileGeoData.getXRes());

Any - would be greatly appreciated.
Lee

[LeeB]

Hi,

Sorry but just come to the conclusion that the GeoCoords must be to the centre of the Pixel rather than the top left...hence the 50m offset.

Cheers
Lee