> I've got a bit of time to start working on the NHD import again,
> and after importing both OSM and NHD data into my GIS app, I'm
> not quite sure what to do with it; that is, I don't really have
> a procedure for resolving conflicts visually/manually, let alone
> automating the process.
I don't know of anyone who has a comprehensive pre-upload conflict
resolution solution. Often, the NHD components are not named, and are
harder to locate to match with local features, or they have a different
name.
If the existing data was just a manual aerial trace, the NHD data is
usually better from what I have seen.
> Would like to start a discussion with the NHD contributors about
> creating some guidelines (and documenting those in the wiki),
> beginning with what you are doing so far.
My import procedure has been:
Python script suite at
http://svn.openstreetmap.org/applications/utils/import/nhd2osm/
Upload with bulk upload script
http://svn.openstreetmap.org/applications/utils/import/bulk_upload_06/bulk_upload.py
I have found that NHD extracts often include the same feature ID in multiple
area extracts. I have not found a way to automate detection and removal of
these features yet - I wrote a Perl program to find the NHD feature ID, then
removed them manually in JOSM, but I need to do another fixup on the data
before it can be uploaded (I forget the details).
In addition, there are "duplicate nodes" where different types of water
bodies connect. It would seem to be a good solution to merge those
nodes before upload; after all, different types of hydro features are on the
same level and will connect 99.99% of the time, rather than needing to be
fixed up later when the validator complains. I have no fix for this at
all, but some variation on looking at all NHD data for a previous identical
node and merging them should work.
There may be better GIS tools for this by solving with a geometric point
of view, but I've never worked with them.
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