The maps don't loop correctly

[rubo77]

I downloaded some of the maps, that you get when you switch to the map-view and used them as .ppm maps with the linux xplanet tool to generate new planets, but I noticed, that the maps don't loop, so you get a sharp edge at the point, where one side of the map hits the other:

Is there a bug? and you don't get the whole map? I looked at it and I couldn't find any of the exact patterns you see on the map again on the from it generated planet in you tool???