[mapserver-users] Shift of half a pixel

[Lime, Steve D (DNR)]

What version are you talking about? How do you know there is a shift? That is, what is your reference? Is it possible there's a difference in the bounding box model? For WMS the bbox represents the outside dimensions of the pixels in an image.

Steve

Note: MapServer uses a pixel center bbox model but that difference (with WMS's representation) is taken into account in the WMS code.

From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Fritz van Deventer
Sent: Monday, June 04, 2012 9:27 AM
To: mapserver-users at lists.osgeo.org
Subject: [mapserver-users] Shift of half a pixel

Hi all,

We are trying to get VHR satellite imagery to run as a WMS in different GIS clients. When we compare the original image (we tried different formats, tif, ecw, virtual formats etc.) to the hosted image we see a shift in the pixels. Looks like a minor warp or transform.

We are unable to find what is causing this error. We tried using different output drivers, and different output and input formats. It looks like serving with GDAL as output format and Imagemode on FLOAT32 gives the best result, however in black and white.

If this is a known issue, is anyone able to tell me the (in)accuracy of the shift? Or is it not supposed to happen altogether?

Regards,

Fritz van Deventer - http://neo.nl

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