[Tagging] Buildings blocks

Jean-Marc Liotier jm at liotier.org
Wed Mar 11 11:56:14 UTC 2015


On 11/03/2015 12:22, Martin Koppenhoefer wrote:
>
> 2015-03-11 12:12 GMT+01:00 Severin Menard <severin.menard at gmail.com 
> <mailto:severin.menard at 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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