On Sun, 05 Feb 2012 16:38:11 +0000 Richard Fairhurst <rich...@systemed.net> wrote:
> Hi all, > > In order to assist remapping in the South-West, I've uploaded a bunch of > OS-derived shapefiles each containing all the roads in a 10km x 10km > area. You can use Potlatch 2 to bring these geometries into the map, > saving tracing work. > > To load: > > 1. Open Potlatch 2 at the required area. > 2. Click 'Background' -> 'Vector file...'. > 3. In the text box at the bottom, paste a URL of the form: > http://richard.dev.openstreetmap.org/os/SS20_Road.shp > 4. Untick 'Simplify paths' and make sure 'Shapefile' and 'Lat/long' are > selected. > 5. Click 'Load'. > 6. When the newly loaded layer appears in the table above, change the > style from 'Potlatch' to 'GPS' (more visible) > 7. Close the dialogue > > Then, to bring a road through, just alt-click it. You will (obviously) > need to edit the tags (use Advanced mode) and add connections with other > roads (the J key is good for this). > > Each 10km x 10km square is a different shapefile. To find the URL, go to: > http://geowiki.com/os.cgi > and type the placename, then just copy and paste the URL it suggests. > > I've uploaded road shapefiles for the SS, SW and SX grid areas. If you > would like a different area or another layer (e.g. rivers), let me know, > though it might take a while. Alternatively, I've provided instructions > at the bottom as to how to do it yourself. > > There is lots that could be improved about this workflow: implementing > TagTransform to remap tags automatically, zipping up shape-files, > allowing Ctrl with alt-click, automatically joining streets, etc. I'm > very very unlikely to have much time to do this before 1st April, so > with the best will in the world, it's not worth making "this would be > easier if..." suggestions unless they're really astonishingly simple - > sorry. More P2 coders always welcome. :) > > This is provided as a service for remapping only. It will on balance > improve the quality of the mapping in the South-West, but is obviously > not as good as survey. Some notes on the data: > > - VMD has downsampled road geometries which are of a better standard > than the NPE-traced mapping in large parts of the South-West, but are > not as good as the best OSM work. > - VMD roads are broken at every junction. This makes them more suitable > for country lanes than town mapping. Also, some very dense areas (e.g. > Plymouth) are probably still too large for P2 to manage sensibly. (Plus, > in my experience, dev.osm.org is not great at serving huge files.) > - Names are only present for 'Minor Roads' and upwards, _not_ for 'Local > Streets'. > - VMD is subject to the usual OS OpenData licence. > > cheers > Richard > > > > > > == How to create the shapefiles yourself == > > We need to split the shapefiles into 10km x 10km 'tiles' as 100km x > 100km boggles P2 in busy areas. > > Download the 100km x 100km VMD shapefiles from the OS OpenData website. > Make sure you have gdal/ogr2ogr installed. Then, create each 10km x 10km > tile like this: > > ogr2ogr -clipsrc 290000 90000 299999 99999 -s_srs EPSG:27700 -t_srs > EPSG:4326 -skipfailures SX99_Road.shp SX_Road.shp > > In other words: "clip to this bounding box, reproject from OSGB to > lat/long, write to SX99_Road.shp, read from SX_road.shp". (Yes, ogr2ogr > does take destination and source files the wrong way round.) You can > fairly trivially put a loop around this to produce all 100 tiles. > > Upload the resulting .shp, .shx and .dbf to your webspace. (P2 doesn't > read .prj files so you can ignore those.) Put a crossdomain.xml at the > root of it (you can copy the one from > http://richard.dev.openstreetmap.org/crossdomain.xml) to tell Flash that > yes, it is allowed to read files from there. > A possible alternative to the bounding box procedure would be to obtain pre 2010 datasets, they were published in the 100th sheet format, e.g. SS00 to SS99. I have a copy of the England set I could contribute a copy of. mick _______________________________________________ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
