Hi
I am facing a very weird issue with a mismatch between a geotiff layer and
an postGIS layer.
Let me first explain my data setup and then come to the problem that I am
facing
*Setup*
We are using PostGRES/PostGIS as our data backend, Mapbuilder/OpenLayers as
the UI and a custom built
server as the WFS/WMS server which primarily uses the Geotools API 2.4.0.
*Rendering*
I am rendering the geographic infomation for a city on the map.
This city has multiple zones that is stored in a zone table in the EPSG:4326
coordinate reference system.
This layer when rendered on my GIS map is called the 'ez' layer.
In addition to this we have a basemap layer which is basically a geotiff
file that is also a representation
of the same city in EPSG:32616. This is rendered on our GIS map as the layer
'mapBackGround'.
As far as rendering the 'mapBackGround' layer goes we use a WorldImageReader
to read the geotiff file and generate the GridCoverage.
Once we extract the GridCoverage we get the size of our desired segment that
we want to view and pull it off the image generated by the
GridCoverage, this ensures that we get an image to display exactly within
our bounding box. This image is then sent out ot the
Mapbuilder GUI.
As far as renderign the 'ez' layer goes we simply extract the featureSource
and add it to the DefaultMapContext which is passed on the front
Mapbuilder/OpenLayer
*Issue*
Now coming to the issue we are facing. When the layers are rendered on the
map due to some weird inexplicable reason
the 'ez' layer and 'mapBackGround' layer do not seem to be aligning
properly. There is a slight difference in the
rendering of the two layers. In addition as we move from top left hand side
of the screen to the bottom right hand,
the deviation increases. At higher zoom levels, the layers line up almost
exactly but not perfectly.
Has any one ever faced a similar situation. If yes could you take a guess at
where in the whole
(PostGRes - WMS server - GeoTiff renderer - PostGIS renderer -
Mapbuilder/OpenLayer) hierarchy could the problem lie?
Also could you let me know if there is a more effective way to render
geotiff files as compared to the general mechanism i suggested in the
Rendering section above
In case the above information is not helpful I would be glad to provide more
information. I would appreciate any help
with this issue.
Thanks and Regards
Ajay Ravichandran
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