[Talk-us] Fresno castradal imports

Werner Poppele poppele at hm.edu
Thu Apr 26 14:44:16 BST 2012


Paul Norman wrote:
> I happened across an import of Fresno castradal data from mid-2010 in the
> Fresno area. http://www.openstreetmap.org/?lat=36.77&lon=-119.81&zoom=15 is
> the general area but I haven't fully explored the extents. For a view of the
> data, see http://maps.paulnorman.ca/imports/review/fresno.png
>
> Based on source tags this import was of about 280k ways and their associated
> nodes. This likely totals about 1M objects.
>
> The tagging of a typical lot is as follows:
>
> attribution=Fresno_County_GIS
> fresno_APN=44329204	
> fresno_TX_area_CD=5199
> fresno_lot_area=0.17
> fresno_lot_depth=124.0
> fresno_lot_width=60.0
> landuse=residential
> lot_description=LOT 13 CLINTON TERRACE NO 2
> lot_type=single family residential properties
> other_use=S
> primary_use=S01
> secondary_use=000
> source=http://www.co.fresno.ca.us/%5Cdepartmentpage.aspx?id=16313
>
> Many lots have the fresno_lot* tags as 0.0. This is clearly absurd and the
> object's tags are inconsistent with its geodata.
>
> There are a number of problems with this data. These include
>
> 1. It is castradal data. The consensus is against dumping castradal data
> into OSM.
>
> 2. The tagging hasn't been converted to OSM values. The other_use,
> primary_use and secondary_use should map to something or perhaps not have
> been imported.
>
> 3. There are tags indicating the size of the lot. This duplicates the OSM
> geodata
>
> 4. Some lots are split in half, for example the school in the picture.
>
> 5. There aren't many curves, but what curves I can find are overnoded.
>
> 6. Some objects have no OSM tags at all. For example,
> http://www.openstreetmap.org/browse/relation/957260 or
> http://www.openstreetmap.org/browse/way/61615684 have no tags except for
> metadata from the import.
>
> 7. Some objects don't appear to correspond to anything on the ground.
> http://maps.paulnorman.ca/imports/review/fresno2.png is an example of this.
> The import is approximately the same age as the Bing imagery.
>
> 8. There are duplicate nodes where data was imported on top of other data.
> For example, http://www.openstreetmap.org/browse/node/768314177
> http://www.openstreetmap.org/browse/node/767799968
> http://www.openstreetmap.org/browse/node/767770150
>
> With all of these problems I cannot think of any ways to fix the problems
> short of reverting the import. The tagging problems could be fixed by a
> script but the inherent problems of castradal data cannot be fixed without
> essentially deleting most of the import anyways.
>
> I propose to delete unmodified objects from this import. I will attempt to
> preserve areas like schools and fix them if possible. It should be possible
> to keep most of them but I won't be able to be sure until I get into the
> removal.
>
> Such a removal would have to be timed around the import and mechanical edit
> restrictions that will be in place during the rebuild process. If it
> occurred before or after the rebuild would depend on when the rebuild
> process starts and how long the consultation about this proposal takes.
>
>
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User nmixter has been the user who did the import. I would recommend to 
revert the changeset(s) and delete the useless stuff. In the small area 
I checked there were many errors (overlapping lines, double nodes...). I 
agree, that there is no way to fix stuff. User BiIbo modified many 
objects (about 33 %), but it is not obvious what he really changed.

There are amenity=place_of_worship with religion=xyz or amenity=. What 
do you recommend ? We could keep amenity=school or place_of_worship and 
delete the rest of the tags. There are amenity=public_facility. There 
exists an amenity=public_building, but in many cases public_facility is 
used not only for buildings.

We also have landuse=farm or landuse=wood. Sometimes we have 
landuse=farm combined with natural=water.
I think we should simply delete all objects without any osm-tags.

Tell me if you need help.

WernerP




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