What to do ...
THIS IS WORK IN PROGRESS
What to do ...
- ... if you believe you have exhausted everything in your immediate vincinity to map
- ... it's raining outside and you don't want to get wet
- ... you are liying in bed, sick
Quality Assurance and Geometry Improvements
|We all make mistakes and some of the OSM tools make it exceedingly easy to shoot yourselve in the foot.
Luckily there are number of quality control tools
that make it easy to pinpoint errors and if they are not to complicated to fix, start up Potlatch (you don't really want use it) or JOSM with the offending data already loaded. Try to limit yourself to fixing things in areas you know. If you find a serious error outside of your vincinity try contacting either the last editor of the offending object(s) or other mappers in that region. Don't try to impose your idea of what OSM should be on the whole world.
|If you have found widespread destruction (for example caused by Potlatch users that have inadvertedly moved a road or similar) it may be best to revert the relevant changeset. Except if you are a well seasoned OSM expert (and even then), it nearly always makes sense to discuss reverts on your local mailing list or on your national forum before taking action.||HHH|
|Nowdays high resolution aerial photographs are available to OSM for large areas (mainly from bing). Hoever this was not always the case and there are still big holes in many regions.
Many ways were originaly mapped from a single GPS-track and may be very very rough approximations of the actual route the road follows. A further issue is that once upon a time it was considered good practice to simplify ways to the extreme, nowdays it makes sense to add waypoints to correctly model the road (my personal rule is to add enough points to keep the OSM way always on the actual road surface, assuming that the road is at least 4 to 6 metres wide) . If you find suspected geometry errors, you can either correct them using bing areial images or similar (please read the section on mapping from aerial images below!), or use existing GPS tracks to correct the way. Very often you will find dozen of GPS tracks forming a "track bundle", were there used to only be a single track, which makes it very easy to improve geometry (and is the main reason to always upload your tracks to OSM).
|In the same vein you will often find junctions that have been oversimplfied to the point of being wrong, please correct these too. Examples are roads merging in the wrong sequence, roundabouts with connections in the wrong places and so on.||HH|
Mapping from Aerial Images
You can map without getting wet!
While a big part of the fun in OSM is getting outside and mapping "on the ground", a lot of things can be done from your armchair.
Both in Potlatch (you really don't want to be using that), in JOSM and other editors you can blend in aerial images (at least from bing) and trace streets, houses, streams and rivers and many other things. However there are a couple of pitfalls you should avoid
- out of date images: the images were taken at a specific point in time in the past, and are ALWAYS out of date. This may be by multiple years and some times just a couple of months, under no circumstance should you assume that an aerial image is the true depiction of the current state.
- distortion and bad georeferencing
With other words, when in doubt: don't map and defintely don't move or delete other mappers work.
If you are really bored and sligtly pedantic, you can correct one-off typos (stuff that is regulary mispelled is better, if at all, handled by bots).
Easiest way to find and correct these errors is to use a taginfo server for your local area (see for example taginfo.openstreetmap.ch). Don't try to fix creative tagging or stuff that you wouldn't use, just obvious typos (example: buiding instead of building).