Posted by FTA on 31 October 2012 in English (English).

I have absolutely fallen in love with the JOSM program recommended to me. I am able to edit so much faster than I have been able in other programs. I have noticed a few novice mistakes I previously made have been corrected (splitting nodes and not correctly merging them back, etc.) but I am gaining more knowledge of the program.

Today I just finished up adding some of the bodies of water in the town of Carlsbad and tried out my hand at a relation (to add islands to the river); I hope to extend the Pecos River away towards other towns (at the time of some of the sat photos it was drained due to maintenance so that task might prove somewhat difficult at the time).

Also, I’ve noticed sections of towns that aren’t lined up with satellite while others are…should I spend time moving roads back to match up the satellite perfect, or is it an issue with the satellite image not being projected exactly the same each time? Any comments on that would be very helpful :).

Happy Mapping!

Comment from joakimfors on 31 October 2012 at 20:32

Aerial photos should be aligned to GPS traces made in the area. Preferably multiple traces so you can take an average of them. In JOSM you can enable a checkbox to also download any GPS traces when you download data for an area.

Relevant links:

Comment from kucai on 1 November 2012 at 06:20

Sometimes you just couldn’t determine whether those out of alignment roads is due to editing at lower zoom (potlatch usually, with its thick roads) or … somebody moved the map. I had done the second case myself when I was newly trying out with potlatch, I accidentally moved the map instead of scrolling it. Seems too easy to offset the map with potlatch (don’t know whether that has been rectified).

Nowadays, I just realign everything to bing image if there’s no gps trace to be found. I discovered that in many cases those aerial image is very very close to my own gps trace. (Not that I have super duper accurate gps, but my samsung tab does show separate traces (90% of the time) coming and going on a 6 meter wide road.. now, that’s something! imo). If realignment is still wrong, there’s always tomorrow to realign it again. ;) oh well.


Comment from dcp on 1 November 2012 at 11:49

No need to add to the above advice. As a newcomer, though, please check your edits with


Be careful when editing other contributions. Please read about


Especially relations can easily be mutilated by newcomers.

and have fun. It is addicting!

Comment from FTA on 2 November 2012 at 00:31

Thanks all for the comments and tips! The kind of alignment issues I am talking about is I guess a small one (see below:

I have gone ahead and aligned them as best as I can with the aerial footage. These are moves of maybe a metre or two, not miles. Best!

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