Elliot, Great work on the Baltimore county building & address import. I have local familiarity with the county and your work looks excellent.
David David Jackson | GIS Analyst | Office of the Chief technology Officer (W) 202.724.5135 | 200 I ST SE, 5TH FL, Washington, DC [email protected] | Blog: dcaddresscoordinates.blogspot.com Telework Day: Fri On Fri, Sep 5, 2014 at 10:32 AM, Elliott Plack <[email protected]> wrote: > Now that the building and address import is complete, I am moving on to > some of the planimetrics that make OSM look good but also contain useful > information. Parts of the county have a very good, dense network of > streams, traced by a few users, but it can be difficult to spot some > streams amidst tree cover on air photos. In these areas where hydrology > (streams, rivers, ponds, storm water management, piers, etc) exist, I am > proposing to import public domain Baltimore County hydrology, while taking > care not to overwrite anyones hard work. > > Before I write up a wiki, here are the basic details: > > > 1. I made a model that simplifies the polyline hydrology feature class > with a simplification factor of two feet to prevent "overnoding". In > experimenting, two feet between nodes keeps the data simple on the map, but > typically doesn't result in it looking too jagged. The source data is drawn > with a digital pen and then converted to polyline, so any given 10 foot > segment might have 500 nodes in the source. > 2. I ran Paul Norman's ogr2osm on the result from step one, with a > custom translation to convert the various feature types in the source data > to something compatible with the OSM key/value data model. Here is that > translation: https://gist.github.com/talllguy/52066d13d323f1535f3a > 3. Here is the resulting OSM file of that translation: > http://1drv.ms/1lLHSIm > 4. In JOSM I look for a stream system that is missing. I disconnect > the last segment that would intersect an existing water feature already on > the map, like a river or coastline. I use the 'select all connecting ways' > tool to select the entire system and then copy that to a new layer and > download existing OSM data to that layer. (some tags are purposefully > translated with no type, so I have to go back and correct them individually > and check the data) > 5. I run the validator to look for issues. Null names, and nodes that > don't quite connect are easy to find this way. > 6. Upon solving all validator issues I import the system. > > Notes: > > - I'm not going to mess with importing coastline. Our coast is pretty > good and there are too many ways to introduce bugs when importing > coastline. > - Some of the features like boat docks, ramps, and piers may be too > complicated for import. Those I'd address individually and may just use a > node for leisure=slipway. > - For larger rivers where there is a riverbank in the data, I'll use > the approved water=* tagging. > > Questions: > > We have data on where the coastline is comprised of bulkhead, like where > the coastline is unnatural. Is that relevant to the project? I haven't seen > a bulkhead type tag but it could be considered a seawall. > > As a test, I uploaded a small stream system that had not been traced at > all, the Sawmill Branch, so you all can see how it'd look on the map. That > system is here: http://www.openstreetmap.org/#map=15/39.5217/-76.5440 > > This is will be a very manual process and as a steward of open data, I > will take great care not to undo other mappers hard work. > > -- > Elliott Plack > http://about.me/elliottp > > _______________________________________________ > Imports mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/imports > >
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