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

Cruz Enrique Borges Hernandez cruz.borges at deusto.es
Thu Jan 17 23:01:04 UTC 2013


Fist of all, thanks for the comments. I will answers them in place.

> There appear to be some ways with duplicated way nodes (i.e. a way having
> the same node multiple times, other than when closing a loop). JOSM's
> validator can find these. 

This have already been addressed.

> There are some duplicate nodes. An example can be found at 40.8253351,
> -5.4437406. I'll be talking more about duplicate nodes later.

I am not sure about this (most probably is a duplicate node in the original data) 
but in any case the JOSM validator should catch these. We have tried very hard
to reuse as much nodes and ways as the data allow us.

> The road network does not appear to be consistently connected, for example
> at 40.8182542, -5.4476705

We are already aware of this problem. The road network is probably the less 
interested part of the dataset: they are inaccurate and their geometries are 
completely screw-up. It is only provided because some locals mapper thought
that it can be useful as a starting point in a completely empty place. 

> Tagging:
> 
> You appear to be using landuse=reservoir for unknown water. Most of the ones
> I looked at would be better suited as natural=water. natural=water is also
> better suited for unknown bodies of water.

Geometries with water tags are one of the most difficult tags to translate. 
The problem comes from the original data: it does not maintain internal 
consistency between different towns. Others difficult tags are parking 
spaces and greenfield for the same reason. In the end, all of them (and 
probably others ones that will appear in other regions) should be revised 
manually by the local community. We have already planned to have 
wiki pages with regional information about the import process given tips
about this things.

> Are there any tags that will be used other than those in this sample file?

This is the full list (sorry about the spanish):
http://wiki.openstreetmap.org/wiki/Traduccion_metadatos_catastro_a_map_features

Please, if you found any mistake, let us know before changing the table.

> The import is proposing a new tag, use=agricultural. This is found on
> landuse=meadow areas. Are there any new tags that this import is proposing
> to use?

This is ,almost for sure, a bug in our code. Anyway, the complete list are in 
the previous link.

> How were the tag translations arrived at? 

The translation tags was made from: 
- What catastro documentation said:
 http://www.catastro.meh.es/pdf/formatos_intercambio/catastro_fin_cat_2006.pdf. 
- What experts mappers have said. In fact, the pages have been almost 
completely filled by expert mappers from the Spanish community.
- What persons close to the catastro office have said to us.
- Obviously, our own experience using this data in other projects.

> Taking the example of
> landuse=greenfield, was this decided on based on descriptions from the
> catastro, or was it based on inspection of the areas that it applies to with
> aerial imagery, surveys or other resources?
>
> The areas tagged with landuser=greenfield aren't areas with no past or
> present buildings scheduled for development (i.e. virgin ground that will be
> turned into a construction site)

Our experience over that specific tag is that catastro have overused it: there 
are places tagged (in catastro) as a greenfield that should be another thing 
(normally landuse=village_green or recreation_ground). Probably this is
due to differences in the definitions of the two ontologies.

> If you go for this method, how do you intend to handle duplicate nodes? The
> problem is that if two files that contain nodes at the same position are
> uploaded in two different edit sessions JOSM will not merge the nodes, even
> if they were merged in the concatenated file.

This problem should not happen never. The splitted files consist on an entire 
block of buildings that cannot share any node, by definition. In any case, the
conflation with existing data will be responsibility of the local mappers.

> Other:
> 
> To what extent do you intend the importers verify the data? Do you expect
> them to 
> 
> 1. Verify each object in some way against some other source (e.g. imagery)
> 2. Verify the file for consistency (e.g. that no buildings are in water)
> 3. Rely on cat2osm2's verification

We expect them to use (at least) 1 and 2 and of course the JOSM validator. 
I am not sure on what you mean with 3. 

Moreover, we think that this task should be made ONLY by experts mappers 
who really know the surrounding area in order to be able to fix the 
ambiguities or the mistakes. Even more, probably some of them have to be
resolved "in place".



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