Once the realm of national geographical surveys, the increasing availability of affordable GPS devices means that it is increasingly possible to 'crowdsource' cartographic information (that is, map information) and generate maps that rival professional maps from user uploaded data. Where local infrastructure is such that you are more likely to find a dirt track than a recently laid motorway, local maps produced by tracking the daily movement of local travellers means that crowdsourced maps may in fact be more accurate than formally surveyed ones.
OpenStreetMap, or OSM, is the result of an international collaborative effort in which individuals can view, edit and maintain an increasingly accurate map of the world as it is today. In the same way the Wikipedia relies on the activity of volunteers, so too does OpenStreetMap.
OpenStreetMap follows a five step process in the production of its maps. First, data is collected using GPS devices; the GPS traces are then uploaded to the OSM website, and transformed into the representation used by OSM. The next step is to label the routes so that they can be rendered correctly. The final step is to generate the actual graphical map tiles.
Other approaches to collaboarative mapping, such as Google's MapMaker, allow you to edit maps directly without the need to upload GPS data.
The following video shows how OSM maps can become increasingly detailed over time; in this case, we see how the Dutch port of Antwerp was mapped over a period from 2007 to 2009.
A second key feature that distinguishes OSM from commercial maps is that the data used to generate the maps is available under an open license. What this means, among other things, is that it is far easier for you to use the data for your own purposes. So for example, one service that I particularly like is called CloudMade, that makes it possible to add you own 'skin' (that is, your own colour theme or design style) to a map and share it as well. (So if you create your own Digital Planet for CloudMade/OSM, why not share a link to it on Twitter, using the #digitalplanet and #open2 hashtags?!:-).
So, wherever you are in the world, why not check out OpenStreetMap. And if you notice that the map isn't quite as accurate as it could be where you live, if you have a GPS device, why not consider uploading some of your own data to the map? Alternatively, why not try out Google MapMaker - it's currently open for editing locations in much of the southern hemisphere.
Or if you're looking for an even easier way in, why not try Google MyMaps? Google MyMaps let you annotate a Google map on your own map overlay with markers that identify points of interest to you. If you're fortunate enough to have an Android phone, the Google MyMaps app makes it one-click asy to add markers corresponding to your current location. But even without such a device, it;s possible to edit your own MyMap through any modern web browser. Even if you only add one or two points a day, it's amazing how quickly you can create a richly annotated map.