[Talk-us] A Friendly Guide to 'Bots and Imports

David Carmean dlc at halibut.com
Thu Aug 5 21:29:19 BST 2010


On Thu, Aug 05, 2010 at 01:38:36PM -0500, Ian Dees wrote:


> I think the NHD "import" is a good example of a well-intentioned importer
> (me) gone wrong. I had initially planned to import the whole darn thing in
> one swoop, but various technical and life challenges came up before I could
> get it going. While I was working on those issues, people started importing
> it themselves (sometimes marking so on the wiki, sometimes not). Now that
> there are some areas imported, the import of the whole dataset becomes
> infinitely harder because we have to match existing data with new OSM-ified
> data.

And I'll add my own mea-culpa.  I created some wiki pages/features to
help partition and coordinate NHD import efforts, and then also found
that I didn't have the time to follow up.

I would agree that the partial imports will have increased the difficulty
of a large-scale bulk import, but we already had hydrographic features
from TIGER, did we not.  And hand-drawn features from aerial traces and
actual boots-on-the-ground mapping.  Conflation in general is a tough
problem, I gather.  There are tools, algorithms and heuristics in the
GIS world but the OSM data model makes translation between the two models
somewhat difficult.

For example, something that looks very interesting which I plan to examine
is the Java Conflation Suite [1], which looks like it could be used over
relatively small areas (probably about the size of the API limit... 0.25
degrees square?).  But as a component of the JUMP[2] platform, it operates
only on Shapefiles and GML out of the box.  (If we could get some Java
expertise I think it would be very worthwhile working with the JUMP team
to create an OSM driver.)

At any rate, while I think we could mitigate a number of problems 
given some development effort, I also agree that we might want to 
spend more time thinking about why we want to make the imports--and 
perhaps publically debate, if only in talking to yourself on the 
project wiki page, the pros and cons of a particular import.



[1] http://www.vividsolutions.com/JCS/
[2] http://www.vividsolutions.com/jump/





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