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Mapping is done in two steps:
- First, you need to know where things are, mainly the streets and ways.
- Then you need to know what there is, namely the POIs, street names and types. You can do these one after another, or both at the same time, but you can hardly do the what before the where.
- 1 Getting the shape of streets
- 2 Getting the details
- 3 Colourizing the map
- 4 General issues
- 5 See also
Getting the shape of streets
Main article: Recording GPS tracks
The basic technique for mapping roads, footpaths, ferry crossings, ski routes, etc. is to just turn the GPS on and let it record tracklogs as you move. These --- provided they are in the WGS-84 datum, which is the default --- can be uploaded directly to OpenStreetMap and displayed on the editing map.
Set the GPS to record points as densely as possible. On the Garmin systems this is in the "Tracks", "Setup", "Resolution: Highest" menu.
Several applications let you record GPS tracks with your laptop, PDA or mobile phone, provided there is a GPS receiver connected.
Getting the details
A more theoretical approach to the recording of details is in the making at Geotagged meta data.
High resolution Satellite/Aerial Imagery
Main article: Tracing Aerial Imagery
Many cities have high resolution georectified aerial photos available for them which can be used to aid mapping. Due to licensing concerns of the derived data, you should use only public domain imagery, or imagery where this is explicitly allowed (such as Bing aerial imagery). This also aids building the map later if you're using an editor that supports using aerial imagery as a background.
See Aerial imagery for a list of possible sources for tracing.
Improving the map with high-resolution photography
In 2010 a number of sources of high-resolution aerial photography became available for use in OpenStreetMap.
In some parts of the world these give mappers the opportunity to redraw the existing map more accurately.
Things to watch out for
Sometimes photographs are displaced away from the real position of the features that are photographed. You should check that the roads in the photograph are aligned with the GPS tracks that people have contributed to OSM and move the background if you need to.
Something else to watch out for is features that have changed on the ground since the photographs were taken. It is best to use local knowledge alongside the pictures to avoid this.
You can redraw roads with more points on curves to follow the road on the ground and you can also straighten roads that really are straight. You can also look for roads with markings dividing the lanes and tag them suitably; check for tagging advice in your country but this often means highway=tertiary or above when more than a short stretch near junctions is marked.
High-resolution imagery is one of the few practical options for mapping Buildings. Since each town and city could have thousands of buildings, you'll need to decide where you want to start. Maybe doing all the buildings for organizations such as churches, schools, community buildings. Maybe you start with the downtown or a major shopping centre. If you want to tackle a whole town, try to focus on the larger buildings and work one a specific area at a time. Aerial imagery is not always up to date, so you may have to rely on your own notes or memory to image some of the newer buildings.
When photographs are taken at an angle the tops of buildings (especially high ones) are a distance away from their correct position. You can move the traced outline of the building so that it is aligned with the base of the building on the sides where you can see it. For some tips how to draw buildings, see Roof modelling.
Main article: Points of interest (POI)
GPS receivers make it very easy to mark waypoints. On the Geko for example, "Mark", "OK" will insert a numbered waypoint. In the example shown, the cartographer stopped in a pub car park, and 