User:SK53/How can I contribute to OSM without a GPS or Aerial Imagery?

From time to time newcomers to OSM are disappointed to find that the available imagery of their hometown is too lacking in detail to use for street-level mapping. The usual answer is "Get out on the streets with you GPS!" This seems inadequate for people who may well be time-rich but money-poor, and is particularly inappropriate for people in poorer countries when one of the great things about OSM is its ability to act as an enabler for all sorts of people in societies round the world.

These are various suggestions about the type of resources which can be used in the absence of either a GPS or Aerial photography. I do assume that landsat satellite images are available and the area is not seriously obscured by clouds.

Using Landsat (Yahoo)

If no aerial imagery of your area is available from Yahoo, there should be satellite imagery. This has a maximum detail of about 10m, but if you know an area it is surprising how much detail it is possible to extract from an image.

If you know an area a lot of information can be extracted from the satellite images. Rivers and railway lines are usually surprisingly easy to pick out. Also extremely useful is to mark the inhabited areas of towns and villages with landuse=residential. All of these things help because they provide guides for location of more detailed mapping. I've used the Yahoo satellite images to map forests before I've visited an area and been surprised that I was only perhaps 10-20 metres out in accuracy.

Names

If main roads which have already been mapped lack names, then adding the names is a very valuable activity. Also there may be place names which have been imported from the GNIS database, which may be wrong or inaccurate. This sort of information makes the map more useful, and can only really be collected by someone local on the ground.

Walking Papers

See the wiki. These enable a part of the map to be printed out in such a way that the paper map can be accurately located. These are an essential tool for mapping whether you have a GPS or not. If you can get the major streets surrounding an area mapped from yahoo, then you can make walking papers and use these to start recording streets and POIs. Of course complete accuracy is impossible, but you'd be surprised how good the human eye is at estimating things. Streets tend to be fairly constantly spaced, and distance can be judged by counting steps or paces. The important thing is that the topology of the roads and paths is maintained.

Digital Camera

If you have a digital camera its possible to take lots of photographs which can be used to map POIs and other features. Ideally these can be geolocated, but unfortunately we are not allowed to use Google Maps for this, although it is possible to use OpenStreetMap!

Borrow a GPS or GPS-phone

Some people have managed to borrow a phone with GPS from friends or work, and use it for one day to collect GPX tracks so that they have the correct lines for the important roads and paths. I seem to remember reading a post about someone travelling around on the back of a motorbike or scooter doing this. Doing this before using Walking Papers would enable more detailed mapping.

Its a Wiki

Above all remember it's a wiki. If something is valuable it can be updated and improved. If you're not happy that something is accurately located just stick a "fixme=location approximate" tag on the node or way.