I've downloaded NASA's 500m Blue Marble imagery (July 2004 with bathymetry, to be specific). NASA distributes them in 8 PNG tiles with no world files or anything else. I used a site online ( http://egb13.net/2009/03/worldfile-calculator/ ) to calculate world files for each tile based on their coordinates, 500m/pixel, and their size of 21600x21600 px. Then I swiped the projection file from the mosaic demo and copied it for each tile:
DATUM["World Geodetic System 1984",
SPHEROID["WGS 84", 6378137.0, 298.257223563, AUTHORITY["EPSG","7030"]],
PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
AXIS["Geodetic longitude", EAST],
AXIS["Geodetic latitude", NORTH],
I used gdal_translate to make tiled compressed (deflate) geotiffs with the -a_srs "EPSG:4326" option. Then I made external compressed overviews at 2,4,8,16 levels with gdaladdo. Then I made a tile index with gdaltindex.
When I try to create a layer using this new shapefile, I get the "Could not list layers for this store, an error occurred retrieving them: Unable to acquire test coverage for format:ImageMosaic" error. I can add each of the geotiffs as individual layers and create a layer group out of them with no problem; the coordinates are right and everything. The mosaic won't take it though.
I'm running the latest Geoserver on Tomcat6 on Ubuntu Natty; GDAL version 1.6.something. I know about the memory leak listener/JAI issue; I tried the "copy imageio and jai jars to tomcat/shared/lib" solution but that prevented Geoserver from even deploying, so I turned off that leak listener in the xml file instead.
I had used Mapserver in a previous job with the above technique and it worked like a charm. I've been curious about Geoserver for a long time, even tried it out for that job but was never able to solve this issue.