Thursday, April 3, 2014

Contributing to OpenStreetMap

Google Maps is great when it comes to accuarcy of their maps. They offer the best satellite imagery and a deeply detailed set of vector data. As long as you want to check a route, see your house from above or look for whales in the ocean, you will be satistfied by the provided service. As soon as it comes to use the data for GIS projects you will be lost because Google's Terms of Use prophibit you to utilize their data. 
Therefore, OpenStreetMap is a great alternative to get global data for your GIS project. OSM data can be used by everyone for everything because all contributions are under the Open Database License. Several GIS applications like QGIS and ArcMap can be extended by plugins that enable you to extract data from OSM.

Although OSM is not providing satellite imagery, their vector data gets better every day. Everyone can contribute and start digitizing data. To see current changes, I recommend to go to Show Me The Way.

Due to my intentions to use GIS data of my current homebase Kisumu, Kenya, I realized that Google is offering much better data in the study area. In Nyalenda, a slum close to Kisumu's city center, motorcycle taxis are crucial for the public transport. The gravel roads are muddy and clutterd with potholes, which is why there is few competition by regular taxis or Tuk Tuks. 

For the Bachelor's thesis, I want to identify service deserts according to the motorcycle taxi stages and the road network. As you can see, Google already has some of the major gravel roads in Nyalenda digitized.

OSM obviously lacks a lot of these roads. And the ones that are already in Nyalenda have been digitized by me in a test run.

Screenshot of OSM to show current status

Digitizing data for OSM is very user friendly. As soon as you have created your OSM account, you can start contributing. For beginners it seems to be recommendable to just use the embbeded editor and absolve the short introductional tutorial. 

The OSM vector data will overlap the bing satellite imagery, which is used as template. After adding some lines that cover undigitzied roads, you can add attribute values like surface, name and so on.

Digitizing road in Nyalenda with the embedded editor

For sure, digitizing is very time consuming, but I like the idea of contributing to such an influential project. It trains your skills and sometimes you can help yourself, like I do in Nyalenda.

I hope that I will find time to continue the work for Nyalenda soon. You can check my proceedings here: OSM Nyalenda 

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