Hello, I am a new subscriber to this list. I live in the Atlanta, GA area. I have been adding to OSM a little in my spare time but now it seems to be getting closer to my work life.
I have worked a bit on adding OSM as a background layer to our GIS, but today I found this mailing list with this discussion and now I am also thinking about going the other way and adding hydrography to OSM. In my work I have been using the recently released NHDPlus dataset: http://www.horizon-systems.com/nhdplus/ Is this the version of NHD this discussion has been about or has this been about a previous version of NHD? The most interesting layers I see in NHDPlus are all in its Hydrography folder: nhdflowline, nhdpoint, nhdarea, and nhdwaterbody. (A second line layer, nhdline, is present but seems to be mostly unused. Many other layers are also present in NHDPlus.) The nhdpoint layer is small and indicates where waterfalls, springs, rapids, wells, and locks are located. The nhdflowline layer is just lines and they represent all the waterways in the nation down to fairly small streams. The nhdarea and nhdwaterbody layers contain 2-dimensional areas that are present only when a body of water is wide. All of these layers contain many shape attributes that are likely of no use to OSM. For the whole nation, here is a summary of the uncompressed size of all the Hydrography shapefiles (including dbf): nhdflowline 2.8G (or 2.3G for just the .shp) nhdarea 140M nhdwaterbody 585M nhdpoint 26M nhdline under 4M Grand total 3.5G, (goes down to 1.6G when zipped) I really like the idea of having detailed hydrography added to OSM, but I am a little worried about overwhelming the database by adding all the flowlines. I am thinking that just adding the nhdarea, nhdpoint and nhdwaterbody might be a good place to start even if we do end up adding the flowlines too. A quick looks indicates that filtering by which flowlines have GNIS names assigned might cut the number of flowlines roughly in half. This could be an easy way to omit the "least interesting" streams but after a quick look I can see it would leave many named streams disconcertingly disconnected from the network because the stream they flow into lacks a name. -- Mark Gray _______________________________________________ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk-us
