The Players: Okay, I admit it, I'm not much of a bash scripting person. Actually, I'm not much of a shell scripting person. Everytime I need to use sed or awk, I spend a lot of time Googling to remember correct syntax. So I've written a script, but it doesn't quite work, and I'm hoping lazyweb (read second paragraph of http://en.wikipedia.org/wiki/Lazyweb if you've never heard of lazyweb) can help out.
Yan Morin has done a wonderful job of taking the NHN data and converting NLFLOW and WATERBODY over to OSM format [ http://osm.progysm.com/rncan/geobase/nhn_rhn]. Unfortunately, the tool he used "bins" ways at seemingly random instead of geographically (the purpose of the binning is to write out multiple files that are smaller). Those people who have done importing of nhn flow will know what I'm talking about. So I wrote a script that will take some RWeait sed-foo and combine it with Osmosis to merge all the nhn files and then split/bin them back out using geographical bounding boxes. The Set-Up: Download Osmosis 0.35 from [http://wiki.openstreetmap.org/wiki/Osmosis]. I've written the script to use 0.35 because that's the last release that had official support for API 0.5 files. You could use Osmosis 0.35.1, but things are less guaranteed, I guess. Unzip Osmosis into your home directory, so that the osmosis executable can be found at ~/osmosis-0.35/bin/osmosis. Create a new directory somewhere else in your home folder (perhaps ~/osmfiles/nhn/08HE0X1 or maybe ~/nhnfiles/Tahsis) to store all the files for a single water basin from Yan's server. Download *all* the files for a single water basin into that directory. Download the script (attached) and put it anywhere on your computer, and make it executable (chmod u+x nlflowrebox.bash). The Hook: While in the directory that contains all (and only) the files for one basin, run the following command: ~/path/to/nlflowrebox.bash You'll get a bunch of files, named similar to Split_49.58_-126.00.osm, which is the lat/long of the bottom-right corner of the bounding box for that file. Start importing using Josm. You'll also get a _COMPLETE.osm file, and if the area is really small, or you have lots of ram, you could just use this instead of the bounded files. The Shut-Out: Watch it fail. At least on my computer. If it works on your computer, you're very lucky. For some reason, I keep getting errors about how it can't find the osmosis executable, or how osmosis can't find the file ("But it's right there!"). If anyone knows how to fix the problem, or how to improve the script in other ways, I'm open to suggestions or patch files (preferably patch files). The Wire: There's a way around the problem though. I've set up the script to print out the two commands that it's attempting to run. So all you have to do is run the command once, then copy the part that says "Merge command is ~/osmosis-0.35/bin/osmosis --read-xml-0.5 ........ --write-xml file="NHN_NLFLOW_COMPLETE.osm" (only don't copy the "Merge command is", just copy the "~/osmosis...") and paste it into the command line and run it. This will create the fully merged "complete" file. Then you run the nlflowrebox.bash command again and copy the "Split Command is ~/osmosis-0.35/bin/osmosis --read-xml .....--write-xml file=Split_49.98_-126.80.osm" (only don't get the part that says "Split Command is", just the stuff after), and paste that into your command line and run it. You'll get all the split files for your importing pleasures. The Sting: There's still some minor problems; dealing with duplicate nodes. You'll find that duplicate nodes are still there where ever two or more streams intersect. Either fix these using Josm validator or send me a .patch. Also, any way that crosses a bounding box boundary will appear in both bounding boxes, so be careful when importing along file edges. The Tale: Here's what I really would've like to see for a splitting/binning system such as this: topologically aware binning. Hydro flow data is almost an acyclic n-ary tree graph (not quite acyclic, but close). It would be nice if there was a binning system that could perform a "reverse depth-first search" and add ways to a file starting from a leaf way and slowly adding siblings and parents until a max number of ways is reached. Then it continues by adding into a second file, and a third file, etc. This would be better at binning things like rivers/creeks. I don't think such a system exists for OSM, and I certainly don't have the gis skills to pull it off. Chapter titles are courtesy of a Newman/Redford/Shaw movie (though slightly reorganized). Adam
nlflowrebox.bash
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