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Keeping local copy of data?

In JOSM one can save the data layer and load it later, it also has the ability to update the map. Seems like a good idea - download once, than only update, saves my time downloading, saves server time sending, I can work offline and later somehow merge the edits if needed.
What is bothering me is that the updating looks very similar (same) as fresh download. Working on a big (city) are stops being so smooth and convenient.

Does it have any meaning to have local copy of data and update it compared to fresh downloads for each edit? Any advantages I did not mention? Any hidden drawbacks?

josm local-copy

asked 08 Dec '11, 23:13

LM_1
3.3k●33●51●88
accept rate: 10%

One Answer:

If you do not have any pending edits, I'd recommend, starting from scratch with a fresh download.

Update data is a shortcut for the following actions:

Downloading all the bounding boxes of the current data layer. (This is not faster than the initial download. In fact, it is the same API request.)
Merging the fresh data with your (modified) old data. (Similar to merging two data layers.)

Update can be useful when you like to check for conflicts. Also, it's handy, if you have many small boxes and you want the most recent data, but downloading the boxes one by one would be too cumbersome.

Note that Update selection and Update modified work differently: The bounding boxes do not matter; JOSM will request only data for the selected / modified objects.

answered 09 Dec '11, 10:41

bastik
651●3●9●19
accept rate: 41%