There are two camps opening up in the Volunteered Geographic Information (VGI or community generated content CGC) community that are sure to have big import going down the line. One is OpenStreetMap.org (editor | download) and the second is Google’s Map Maker (not available in the US and other developed world locations) (editor | tile view options | download). Both services allow users to either upload their own GPS track or digitize linework and points off satellite imagery. These two options have added to the global map, often creating the first detailed map of a place ever available to the general public.
But the two projects have very different license structures (OSM almost unrestricted, Google very restricted). Not only do they duplicate effort, but they result in “similar but different” products that do not perfectly register with each other. This is an problem that faced many in the US in the 1990s as many organizations developed their own, not-interoperable datasets for the same regions. That model has largely been replaced by single entities building fundamental datasets that other organizations and individuals repurpose.
The licensing and data coverage & registration issues are of note to professional cartographers (and first responders) more so then to the general public. But, as Sean says:
OSM and MapMaker aren’t talking and I think it is a big problem – if you want to help rescue efforts in Haiti where do you go to digitize? OSM? MapMaker?
Muki Haklay has a good comparison of the detail in each of OSM and Map Maker for Haiti. In the map here, yellow means that there is a better coverage in Map Maker, and blue means that there is a better coverage in OpenStreetMap.
Screenshot below, click for larger version.
“The comparison looks at total roads length for both datasets. The calculated difference between them using the equation:
∑(OSM roads length)-∑(Map Maker roads length)
for each 1km grid square.
The information in the file can be used for the following applications:
- Users of these mapping products - it can help in judging which dataset to use for each area.
- Users – it can facilitate conflation - the process of merging datasets to create a better quality output.
- Mappers - it can illuminate which areas to focus on, to improve coverage.”
Haitian Earthquake Emphasizes Danger of a Split Geo Community (seen over at FortiusOne’s Off the Map blog advocating for Creative Commons 0 “zero” licensing of geodata during disasters) has a overlay of OSM (Open Street Map) and Google Map Maker data.
And finally, before and after images of OpenStreetMap.org map for Port-au-Prince, Haiti:
OSM just after the Earthquake