I downloaded tiles from Copernicus EU DEM. Each tile is made of four files :

$ ls *E30N30*

I guess these are WorldImage files ? Now I am trying to create a store from them in GeoServer. However the WorldImage store type only seems to accept single WorldImages, and the ImageMosaic store type fails to load data with

Could not list layers for this store, an error occurred retrieving them:
Failed to create reader from file:///data/source/Copernicus_EU_DEM_v1.1 and hints
Hints: REPOSITORY = org.geoserver.catalog.CatalogRepository@433abb55
_EXECUTOR_SERVICE = java.util.concurrent.ThreadPoolExecutor@13eb5bc5[Running, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 0]
System defaults:
FILTER_FACTORY = FilterFactoryImpl
FEATURE_FACTORY = org.geotools.feature.LenientFeatureFactoryImpl@2081b1a2
STYLE_FACTORY = StyleFactoryImpl

(I had a similar issue with another dataset earlier because the dataset directory was missing write access for tomcat user. This is not the same case here, the permissions are right.)

How am I supposed to load these tiles ?

1 Answer 1


The problem is most likely that GeoServer can't work out the projection of the world image files. If you import them individually it will ask you for the projection before displaying them. In the case of an image mosaic there is no provision for asking you for the projection of each tile (it would take too long).

So you have a variety of possible solutions:

  1. Add a .prj file to each of the tifs to tell GeoServer what the projection is - I wrote a blog post about a small tool I wrote to do this.
  2. Use GDAL tools to convert the files to a "real" GeoTiff with the projection correctly set. Something like:

    gdal_translate -a_srs epsg:xxxx in_file.tif out_file.tif 
  3. Stuff all the tifs into a VRT (setting the projection with -a_srs), convert that to an image mossaic (or pyramid) using gdal_retile.
  • I tried the second solution which seemed the quickest to test, and after moving the new GeoTiff files into their own directory I was able to load them as an ImageMosaic. Jun 10, 2020 at 9:18
  • Do the three options provide exactly equivalent results ? Jun 10, 2020 at 9:19
  • pretty much I would expect - building a more optimal mosaic might be best for abosolute speed
    – Ian Turton
    Jun 10, 2020 at 9:48

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