[Talk-us] Fresno castradal imports

Toby Murray toby.murray at gmail.com
Thu Apr 26 19:43:45 BST 2012

On Thu, Apr 26, 2012 at 9:39 AM, Martijn van Exel <m at rtijn.org> wrote:
> Hi,
> On Thu, Apr 26, 2012 at 12:54 AM, Paul Norman <penorman at mac.com> 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
> A few observations:
>> 1. It is castradal data. The consensus is against dumping castradal data
>> into OSM.
> I am not aware of such a consensus - consensus among who? Is it documented?
> I would expect such a consensus to appear in the Import Guidelines but it
> doesn't.
> Or do you mean there's a consensus against dumping data into OSM in general?
> If by 'dumping' you mean 'importing without consulting the community and
> without giving proper thought to attribute mapping and generalization /
> normalization of geometries' then yes, I'd say there's a consensus against
> doing that. I don't see why we would not cherry-pick useful and good
> cadastral data for import into OSM, however. It may be our only source of
> things like building outlines (are those generally in cadastral data in the
> US?) or address data in many parts.
> I don't mean to be nitpicking here, I just want to clarify what this
> consensus actually is so people looking for guidance on importing in the
> future can be more fully informed.
> [...]
>> 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.
> Are these problems inherent of cadastral data in general, of this dataset in
> particular, or of the way this import was conducted?
>> 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.
>  The list of issues is long enough and the issues serious enough to warrant
> a revert.
> What I'm missing from this list is the issue I consider to be the most
> serious, which is that this user apparently has not consulted with anyone in
> the community about this import. Or has he/she?

I think the area where there is fairly good consensus is that mass
imports of plot boundaries is not welcome in OSM. There was an attempt
last year at doing this in Arkansas that ended horribly with a blocked
account and a couple hundred thousand empty nodes.

In this case we have another instance of someone not considering the
consequences of their import on the OSM community. Even if the data is
good and valid (which doesn't seem to be a proven point in this case)
if current tools are not able to deal with it, perhaps the import
should wait and effort put into improving tools first.


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