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I have a GeoTIFF with internal overviews, generated using gdaladdo and the -r mode. I published this GeoTIFF in GeoServer 2.6 and I can see the image fine in map preview.

However, when I load the image in our OpenLayers 2 application, the image quality is worse. It appears as though GeoServer Map Preview is using the GeoTIFF overviews that I created using Gdal and that OpenLayers 2 is generating a new overview, using another resampling algorithm.

The layer is loaded in our app by using straight OpenLayers.Layer.WMS Is this even possible? Or am I imagining things?

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It was because a difference in the app projection (EPSG:900913) and the layer registered in GeoServer (EPSG:4326). Because of that, the tiles were reprojected using the default method (nearest) and making the image look bad. I publish a new layer in GeoServer, using the correct Web Mercator projection, with overviews created using mode method and now everything looks OK.

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It may well just be that your app is using a different set of zoom levels, which happen not to match so well the existing overviews

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  • I'm a bit newbie in openlayers. Is ther a way to check the zoomlevels that my app is using? Can I use the scale text (eg. 1:17M) to see if the zoomlevels are the same?
    – Daniel
    Commented Nov 24, 2015 at 23:04

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