[Imports] [Talk-es] [Cat2Osm2] Tool for exporting Spanish Cadastre data in OSM suitable format

[Cruz Enrique Borges]

> "The height of a building gives a lot of information about the people 
> living in that building" - please explain it. For me it sounds amusing

The information about the height is code as "number of floors" in the 
source file (catastro). Even more, you can make a fair guess making 
"3m = 1 floor" (as is what we are doing when exporting). 

Now, you have the "total surface" of the building multiplying the number of 
floors times the build surface area. Next, you have several possibilities 
depending of what you are doing and the information you have:

- In the worst case you can estimate the mean number of person per square 
  meter with the population data from the National Statistics Agency.
- If you have information about the total number of person in the building
  you can "fain grain" the information. For example, in our work, we have a
  fair estimation of the number of individual houses that there is in a 
  particular build, so we can have the person/per build information 
  (this information in given by a enterprise and is private but national agency
  have this information, we are not ).
- Now you have a estimation of the "local density" of the area. High density
  areas normally consists of tall buildings in the city centre while low density
  consists of suburbs areas. And now you can start characterizing the zones
  if you like.

And most important of all, we are talking about GIS here, if you want or need it in
the other way, you can create the union of these geometries. But you can't do it from 
backwards, from one building get the separated parts.

> From the aerial images it looks like 2, maybe 3 free-standing houses for
> a single family. It is very difficult to determine that from the
> data you imported because the houses consist of 3 to 5 separate
> building ways all of them tagged in exactly the same manner.  You 
> will need to do a complicated geometric analysis and add a lot of 
> guess work to determine the actual number of houses.

This could be a problem, but please note that we have the parcel information
too. With this data you can make the fair guess that you will have one 
building per parcel. Note that the case with non adjacent builds is trivial 
as you can just take the union of all the polygon as the base surface and the
highest height or, as we are only interested in the surfaces, just take them
as different builds. Obviously with this kind of guessing you will make lots
of mistakes. For example in adjacent houses but normally if this case is
mapped as a whole block and you don have any clue of the number of houses
or the total surface. Even more, this can be guessed using the parcel information 
an/or the policy number and stuff like that.

Please note that, in this case we are not interested in the "number of houses"
as this is public information (at least in the Spanish Statistic Agency).

Of course, this type of information complicate the analysis BUT you can still
make the same calculation your are doing now AND you can do lots of new things.

-- 
Cruz Enrique Borges Hernández
Email: cruz.borges at deusto.es

DeustoTech Energy
Telefono: 944139000 ext.2052
Avda. Universidades, 24
48007 Bilbao, Spain