JOSM opening big maps


I am trying to open the map of Poland with JOSM but the program freezes after a while and gives a heap error. Merkaartor also freezes. Any way of importing country OSM file to edit them?


You can try to allocate more space to josm using the -Xmx call, but ultimately you can’t open really big maps in JOSM no matter what you try. The biggest “usable” large map I’ve opened is a 13 Mb bz2 file (not sure how big that is uncompressed).

For example,

java -Xmx1500m -jar josm-tested.jar 

will allocate 1.5 Gb of heap space to JOSM. Obviously your system must have this amount of RAM to start with.

I have worked with a 420 MB uncompressed file as a second layer to compare road networks. I didn’t edit the 420 MB layer however. I gave 4G of RAM to JOSM.

How about uncompressing the OSM file to individual files first or something like that, ie, preprocessing. All I want to do is open a map of a country and view it, so could I preprocess once and use the files from then onwards? Thanks.

My recommendation is to download only the part needed for editing. Downloading and changing are much faster and the risk to change something by accident is much lower.

JOSM is great for editing but very limited for viewing a whole country because all details get drawn on each zoom level. To circumvent this different filters at different zoom levels could be used. But there are much better programs for viewing a map which are fast and show more details at higher zoom. Some offer even customizable rendering and routing: OSM wiki: Software