Data Improvements in Benin about appledata HOT 1 OPEN

Just saw this one.

Nice to hear!

Though a little late and though I’m currently not that active in Benin, here my two cents:

• Indeed we stick to “Highway tags Africa” – means: The “highway” tag is chosen following the importance of the road for the road network, and not following the current maintenance state of the road.

• It is important to have the “surface” key (at least with the raw distinction between “paved” and ”unpaved”). As the ”highway” tag does not say much about the actual conditions, there can be a big difference between a secondary road that is paved and a secondary roads that’s unpaved. This information is really important to calculate the time it takes to use a certain road. The “surface” key is therefore as important as the “highway” key itself.

• There is no motorway roads in Benin. I suppose trunk roads are quite complete in OSM. For the other road types you will find missing roads, maybe even for primary. Even important connection roads like primary roads are sometimes unpaved. The tracing quality is partially very bad, because some roads where traced from extremly-low-resolution landsat images. There is also a considerable number of roads that are badly aligned. Probably because the first contributors did not have GPS traces to align the satellite images. Fixing this would be great.

• You might find places that seem like OSM errors, but are in fact correct. Places like Sô-Ava where you see a lot of houses without any road in OSM, no connection to the road framework, not even a well-defined ferry connection over the river. Or Ganvie where aren’t no roads either and furthermore the houses are in the water. It might sometimes seem strange, but that reflects indeed the situation on the ground. (I’ve been there 😊)

• The most widespread road tagging error in Benin is likely tagging of normal unpaved roads as “highway=track”. “highway=track” should be used only for forestry and agricultural use, but currently it is often miss-used for unpaved roads in general (as it renders in brown in the standard style). This could be fixed by using an appropriate “highway” value (often “unclassified”) together with “surface=unpaved”.

• Don’t worry about roads that have no names in OSM. Almost all roads in Benin do not have a name on the ground!

• Satellite image quality varies. It is worth to try various satellite images for the same place, there are often big differences. During much time, we had no satellite images with good resolutions. The good-resolution coverage of Bing was limited to the centre of Cotonou. In 2016 there was a crowd-sourcing for buying a satellite image not only for the centre of Cotonou, but also the the outskirts and some parts of Grand-Popo. The resolution and the alignment is a little worse than Bing, but the image is more up-to-date. It is available in JOSM and iD be default. Still today it is more up-to-date than Bing. It’s worth considering it. However, DigitalGlobe Premium and Esri have now new high-resolution images also.

• GPS traces are rare in Benin.

• The region where is most construction work going on is around Cotonou: Not in the centre of, but in the outskirts. The agglomeration is growing fast. Of particular interest might be:

  • The zone between Pahou and Cototomey going southward to the Atlantic Ocean: There are many new roads and houses. This is construction within a wetland zone.
  • Hêvié
  • The zone from here at the border of the wetland up to Ouèdo. Some of the new constructions are still not available on satellite images.
  • Ahahonto, Zopah… going northwards.
  • Also some construction work at the east of Cotonou.

Thanks for contributing in Benin. You’re welcome!

Best regards

Lukas Sommer

from appledata.