JOSM - usage questions - beginner

  • Is there a limit to the data that is downloaded? Is it appropriate to download an entire city or county?*

  • Having downloaded the current data for a given area onto, for example, a laptop, is there any reason why editing can’t be done offline (whilst driving around checking street names)?

  • I seem not to get all the data for mid-Cornwall, for example. (I don’t think it has as much data yet as even a small part of London.) I figure this would be the easiest way to work on country roads and small villages as given by rural areas. Maybe I’m doing something wrong with the configuration…? (Admitting I haven’t yet spent a lot of time with JOSM.)

If you are working on a city/area then it seems logical to me that you download that area before you start to edit it. Ok, this may become a problem when dozens of people are editing London, but in general this should not be a problem. That being said; there is a limit on the size of the area that you can download in the web interface (API). It is there to prevent the infrastructure of OSM from being overloading by overenthusiastic users, however no one will stop you from downloading a specific area in multiple smaller passes.

As an alternative you could download the Planet dump which is being generated every Wednesday. Then extract the part where you’re interested in and load it into JOSM as a local file (don’t forget to upload any changes of course). This is an practical solution for any offline mapping.

Note: Do not try to load the entire planet.osm file into JOSM, it will most likely not going to succeed.