I have an ecw file that is an aerial photo in a custom coordinate system. When I publish to geoserver, it specifies the EPSG as 404000. It seems like this isn't actually storing the coordinate system definition. When I preview the layer I can't see the full extent. If I change the declared SRS to EPSG 3857, then when I preview I can see the full extent of the image, but still it won't overlay with other data. However, I can't see the data at all when I load into desktop GIS. I'm wondering if this is due to the size - it is 3GB. I'm new to geoserver so I'm sure I'm missing something- what needs to be done to be able to see this image in the correct loation and overlaid with other data in EPSG 3857, or any other system for that matter?