At Mapbox, we have been looking to improve the coverage of road network in India, which is among the lowest in the world on OSM in comparison to CIA world factbook. We used the osm-coverage tile reduce processor to get a more granular breakdown of highway coverage per state. Comparing these numbers to those officially reported by the Ministry of Road Transport and Highway (MORTH) in India allowed us to better understand gaps in the coverage.
We used GEOnet Name Server's (GNS) NGA data for the names of towns and villages which were missing in OSM and visualised these as WMS layer in JOSM. It helped us in figuring out the via points a national highway is passing and also in adding missing towns and villages.
After that, we extracted states that have the lowest national highway coverage so that we can start to add/improve the roads one state at a time. We used road classification and tagging scheme for India as our guide for tagging the roads.
Improving highway coverage for a state:
We started with the state of Manipur which had only 67.98% coverage of the trunk road network (National Highways) in OSM. We were able to come up with a base workflow which could help anyone who is interested in improving the road network in India.
- First step was to check whether the national highways were already marked in OSM. In order to check this, we used the statistics from MORTH and cross checked the same with the current OSM data.
- Searching for the cities or towns through which a national highway passes was the next step. We used MORTH data for this.
- For the cities and towns which are not marked in OSM, we used GNS's NGA layer to get the approximate locations of the cities/towns. This helped us determine the via route, starting and ending point of a highway. To add the NGA layer follow this post
NGA layer in action
- Finally we checked if a national highway is marked with highway tags, names, and have relations wherever needed. If this was missing, we added names, relations or retagged the roads appropriately.
- Since the names of the national highway is changing from time to time, it was difficult for us to determine whether the data was up to date or not in OSM.
- The towns and villages which were not marked in OSM made it difficult to get the exact starting and ending points for a National highway even with the data available from MORTH.
We invite the OpenStreetMap India community to help us improve road network coverage. Get in touch if you have questions and you can learn more about this project from our mapping ticket.