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

Cruz Enrique Borges Hernandez cruz.borges at deusto.es
Sun Jan 20 13:27:31 UTC 2013


> But in this case would not natural=water be better suited?

After carefully reading the map features page I agree with you. We will review 
all the water related tag.
 
> Well, it's not possible to review them without also looking at the cadastre
> data. For example, how could I verify that what is in that table as "Jardín
> que se valora" should really be tagged as leisure=garden? It's impossible to
> do so without looking at the data from the catastro.

Unfortunately, the raw shapefiles for catastro cannot be redistributed 
without modifications (the modified can be) and you need a valid electronic 
spanish ID card to access them but you can access pseudo-vectorial  
data (a rasterization of the data contained in the shapefiles) through JOSM.
Just download any portion of data from Spanish and JOSM will suggest
using it. We have made that and  LOTS of test with our own towns (and 
several mappers form the Spanish community have made the same) to 
interpret correctly most of the Documentation. Moreover, we have been using
the data from Ciudad Real for a Engineering Project form almost a year 
so we have a relative good experience with both sets of tags.

> It sounds like you are relying on the catastro documentation without
> checking each feature type with another source. This is an extremely bad
> idea for two major reasons:
> 
> 1. It relies on being able to accurately translate the catastro
> documentation into OSM tags. Documentation is frequently unclear or
> ambiguous and words may have multiple definitions.
> 
> 2. It relies on the catastro use reflecting their documentation. I haven't
> seen a large GIS data source yet where there weren't some differences
> between the data source and its documentation.

> My preferred approach is to pick a feature type, find multiple examples of
> it in the data, compare them with imagery or other sources, then use that
> information combined with the documentation to determine what to tag it as.

We completely agree with you. Moreover, we have made that and more. BUT,
and this is and important BUT, we know (because we have talked with
persons close to the cadestre service and because we have see it LOTS of times)
that the internal consistence of their tagging is scarce. We mean, every
civil servant have their own set of "tagging rules" that do not completely match 
one with others. Only in big cities seems to be some sort of "standardization". 
So in the end, we have needed to reach a "tagging consensus" between several 
zones in order to do not fit the tags to only one civil servant "rules". We have 
made test in several towns of the Canarian Islands, Cantabria, Ciudad Real 
(the entire province, in this case), Segovia, and several other (by the local 
community) and we think that we have reach a good consensus. Probably, as
other mappers start using it, some degree of "tagging tuning" should be made
in order to reach a bigger consensus.

BUT, we insists, this is not a tool to realize automatic imports, all data should
be revised by experts mappers before upload, so if any incorrect tag if found 
it will be corrected manually. The changes in the tagging scheme will only 
made things easier for the local mappers but (ideally) they will not change 
the quality of the upload data.

> It's wrong to say that the catastro have overused it. They do not use OSM
> tags. They use an attribute that according to the table is defined to mean
> "Suelo vacante, sin construer," or "Vacant land without building." This is
> different than landuse=greenfield.

What I mean is that, in the internal rules of some of the civil servants, things 
like "Green Zones inside Cities" is tagged that way when they have tags in their 
own tagging scheme, but more specific in their hierarchy. This is what
I mean for "overused", they have used it as a wild-card. The same have happen with 
water related geometries and car parks. The problem arise when, from one place
to others, the wildcards did not match. Obviously, there exist problems also to
translate tags from one set to the other (mostly because the OSM tag set is A LOT
more specific than the cadestre one).



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