On 11/03/2015 12:22, Martin Koppenhoefer wrote:

2015-03-11 12:12 GMT+01:00 Severin Menard <severin.men...@gmail.com <mailto:severin.men...@gmail.com>>:

    I would like to know if putting building blocks in OSM should be
    avoided in all cases. I am currently teaching GIS students in
    Dakar that have ben required to digitize only building blocks on
    their area of study. Could this been done on OSM (and in that case
    how to tag it, as for landuse=residential encompass all the areas
    covered by building blocks and streets?) or always avoided? I did
    not find the answer in the wiki.


There is no general answer to this question. My personal suggestion is to tag them with "landuse=residential" and not include the streets (if they're actually residential areas), or commercial, retail etc. according to what is there. You might also want to split the block into more than one landuse if it is required to better represent reality.

Is it actually the building blocks that they want to map ? Or the urban land plots that often form a unit of habitation in moderately dense African cities ? I suspect that this thread is about the latter.

I am somewhat active in mapping Senegal and I have witnessed many attempts to map the fine subdivisions of the urban fabric - the whole plot mapped as a building, just its limit mapped as a wall, just a name with no other attribute, a landuse, or quite a few other creative misguided combinations that show that people really want to map that even if the editor shows no preset to that effect.

Those not used to map Senegal can take a look at the following orbital imagery for illustrations of what I have in mind:
http://i.imgur.com/jbIe1vB.png
http://i.imgur.com/8BvdP30.png

As you can see, each block is subdivided into land plots - each with a courtyard and several buildings that usually all belong to an extended family. Those land plots have a strong significance and the frequent sighting of spontaneous attempts by to map them in various ways is testimony to that.

I do not yet have an answer to this requirement - it should obviously be mapped as an area but I have so far failed to select satisfactory attributes to model it. I believe that landuse=* is not suitable - in Senegal, as http://wiki.openstreetmap.org/wiki/FR:WikiProject_Senegal recommends, the whole urban area is landuse=residential, so it is not available to map smaller subdivisions.

cc: Augustin who might be able to tell us about how this issue is perceived in Burkina Faso.

(The two images above are also provide good examples of one of my pet peeves: the Senegalese spaghetti way syndrome - this is entirely off-topic but having corrected so many of them over the years I just felt a strong need to share it with someone)
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