Re: [Talk-GB] Postcodes to Shapefile
On 18/03/2011 22:56, Kev js1982 wrote: Resurrecting an old thread I know but with the NSPD Open data also being available allowing Northern Ireland to be generated and having access to an otherwise idle 64bit server I've taken the opportunity to revisit this, and have successfully created the shapefiles (it only took the server 12 days to generate the blighters - it managed to generate Z16 tiles for the whole of Europe and Z18 for the British Isles in just 36 hours - meh!) but now have one more obstacle to overcome... The Veroni thingy obviously generates the tiles so they butt up against one another which works perfectly here in the landlocked East Midlands, but goes somewhat wrong in coastal areas (Fig 1). My thought here is that the World Boundaries shape file can be used to trim the coastal boundaries to be locked to land so that the map looks nice (i.e. postcodes don't end up in the sea save for a little overlap on beaches) - Indeed if you add the World Boundaries file to Quantum GIS and use the Clip Tool you end up with what visually looks correct ( Fig. 3) but if you then hide the World Boundaries file the problem becomes obvious (Fig 2.) What I want to know, is it possible to trim the postcode shapes so that nothing outside another set of shapes (i.e. the British Isles landmass) is included, but instead of leaving gaps the postcode shapes (e.g. FY3 1) are adjusted so that the line runs along the coast line? i.e. I would be left with something visually the same as Fig. 3 but with the coastlines part of the NNXX-X shapefile layer, and more specifically the correct polygon (e.g. the FY3 1 polygon). Kev Fig 1 - Postcode areas in south west Lancashire and the north Wales coast (green = NNXX-X shapefile, blackline and dotted area uses the worldboundaries file) http://kjs.me.uk/3rdparty/osm/SouthWestLancs-NNXX-X.png Fig 2 - After using Quantum GIS's Clip tool - http://kjs.me.uk/3rdparty/osm/SouthWestLancs-NNXX-X_trimmed.png Fig 3 - After adding the World Boundaries back on. - SouthWestLancs-NNXX-X_trimmed_withwb.png /Open Street Map data licenced under the Creative Commons Attribution-Share Alike 2.0 license http://creativecommons.org/licenses/by-sa/2.0/ by the OpenStreetMap http://openstreetmap.org// project and its contributors. /Maps contain Ordnance Survey OpenData http://www.ordnancesurvey.co.uk/oswebsite/opendata/ © Crown copyright and database right 2010./ /Postcode data in Great Britain is provided by Code-Point Open which contains Royal Mail data © Royal Mail copyright and database right 2010./ /Postcode data in Northern Ireland is from the NSPD Open http://www.ons.gov.uk/about-statistics/geography/products/geog-products-postcode/nspd/ which contains National Statistics data © Crown copyright and database right 2010. / On Fri, Apr 30, 2010 at 12:30, Kev js1982 o...@kevswindells.eu mailto:o...@kevswindells.eu wrote: Hi Dave, Thanks for providing the shapefiles for download - they did the job nicely. One thing I have noticed (which also afflicts random.dev.openstreetmap.org http://random.dev.openstreetmap.org) is that a few postcode area/districts are missing - namely FY2 - (North Shore) Blackpool, Lancs PE11 - Spalding, Lincs PL17 - Callington, Cornwall Using the code point download (which I got via the MySociety mirror) shows that these postcodes do exist. Also one of the AB ones (12 or 21 IIRC) for some reason includes parts of Éire, Spain, Portugal and atlantic; while HS includes Reykjavik Just thought you'd like to know there is a possible error with the conversion process. Nice work though - been after a postcode map for a while, and to go from an A5 diagram to full google maps goodness in one swoop is awesome! Regards Kev Swindells. On Mon, Apr 26, 2010 at 5:29 PM, Dave Stubbs d...@randomjunk.co.uk mailto:d...@randomjunk.co.uk wrote: On Mon, Apr 26, 2010 at 5:15 PM, Kev js1982 o...@kevswindells.eu mailto:o...@kevswindells.eu wrote: On Mon, Apr 26, 2010 at 5:00 PM, Kev js1982 o...@kevswindells.eu mailto:o...@kevswindells.eu wrote: Thanks for that Dave - really useful. One question though - which prj string/file do I need for these? Answering my own question - looks to be Google Mercator. http://spatialreference.org/ref/sr-org/6627/ Kev Swindells Actually, for some obscure historical reason it's projected into +proj=merc which is srs 3395. Close to 900913, but not quite the same -- my mapnik stylesheet is then set to reproject to google mercator for the tile generation. Dave ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb You ought
Re: [Talk-GB] Postcodes to Shapefile
On Mon, Apr 26, 2010 at 12:00 PM, Kev js1982 o...@kevswindells.eu wrote: I am currently trying to create a series of shapefiles from postcodes (using OS Open Geo Data) using the code from Random Junk ( http://random.dev.openstreetmap.org/postcodes/#) running on Ubuntu 9.10 but I can't get it working. lots of blah blah about what I did... Think i've sussed most of it... I zapped my pyshapelib folder and downloaded both it and shapelib again With the shapelib and pyshapelib tar gzs inside my osm folder I then issued the following commands tar -xvzf shapelib-1.2.10.tar.gz mv shapelib-1.2.10 shapelib tar -xvzf pyshapelib-0.3.tar.gz mv pyshapelib-0.3 shapelib/pyshapelib/ cd shapelib make cd pyshapelib python setup.py build sudo python setup.py install cd ../../ # The next line is really important if you want python to think this folder has python scripts touch shapelib/__init__.py cp shapelib/pyshapelib/* shapelib/ This seamed to get over the original problem Then you need to ensure you input file has no trailing lines And now to work out why I'm getting Traceback (most recent call last): File makeShapeColoured.py, line 349, in module result = voronoi.computeVoronoiDiagram(pts) File /home/kev/osm/voronoi.py, line 746, in computeVoronoiDiagram voronoi(siteList,context) File /home/kev/osm/voronoi.py, line 206, in voronoi edge = Edge.bisect(bot,newsite) File /home/kev/osm/voronoi.py, line 404, in bisect newedge.a = dx/dy ZeroDivisionError: float division ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] Postcodes to Shapefile
On Mon, Apr 26, 2010 at 1:24 PM, Kev js1982 o...@kevswindells.eu wrote: On Mon, Apr 26, 2010 at 12:00 PM, Kev js1982 o...@kevswindells.eu wrote: I am currently trying to create a series of shapefiles from postcodes (using OS Open Geo Data) using the code from Random Junk (http://random.dev.openstreetmap.org/postcodes/#) running on Ubuntu 9.10 but I can't get it working. lots of blah blah about what I did... And now to work out why I'm getting Traceback (most recent call last): File makeShapeColoured.py, line 349, in module result = voronoi.computeVoronoiDiagram(pts) File /home/kev/osm/voronoi.py, line 746, in computeVoronoiDiagram voronoi(siteList,context) File /home/kev/osm/voronoi.py, line 206, in voronoi edge = Edge.bisect(bot,newsite) File /home/kev/osm/voronoi.py, line 404, in bisect newedge.a = dx/dy ZeroDivisionError: float division These are caused by more than one postcode for the same point -- you'll need to preprocess the input files to remove any duplicates coordinates. There's quite a lot of apparent PO boxes and other odd postcodes in the OS data which result in duplicate points. Also note that it'll use about 6GBs of RAM to run for the complete OS dataset of 1.6 million points. Dave ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] Postcodes to Shapefile
GRASS seems to have some kind of Voronoi algorithm, but I find its interface very non-intuitive, so have not found it to try it out. This may be worth pursuing as an alternative route. As an aside: I notice that virtually all postcode boundaries are obviously created in this way. For instance the Philips Street Atlas shows totally implausible boundaries along the River Trent in S. Notts. Given that postcode boundaries are ultimately determined by logistically sensible walks for postmen, in this case it's pretty safe to assume that the boundary is actually the river. What this means is that by applying a bit of local knowledge and the existing points it is possible to create better delineating zones in OSM than appear in current mapping. Whether this is a good thing to do, or not, I leave for others to decide. From: Kev js1982 o...@kevswindells.eu To: OSM - Talk GB talk-gb@openstreetmap.org Sent: Mon, 26 April, 2010 12:24:26 Subject: Re: [Talk-GB] Postcodes to Shapefile On Mon, Apr 26, 2010 at 12:00 PM, Kev js1982 o...@kevswindells.eu wrote: I am currently trying to create a series of shapefiles from postcodes (using OS Open Geo Data) using the code from Random Junk (http://random.dev.openstreetmap.org/postcodes/#) running on Ubuntu 9.10 but I can't get it working. lots of blah blah about what I did... Think i've sussed most of it... I zapped my pyshapelib folder and downloaded both it and shapelib again With the shapelib and pyshapelib tar gzs inside my osm folder I then issued the following commands tar -xvzf shapelib-1.2.10.tar.gz mv shapelib-1.2.10 shapelib tar -xvzf pyshapelib-0.3.tar.gz mv pyshapelib-0.3 shapelib/pyshapelib/ cd shapelib make cd pyshapelib python setup.py build sudo python setup.py install cd ../../ # The next line is really important if you want python to think this folder has python scripts touch shapelib/__init__.py cp shapelib/pyshapelib/* shapelib/ This seamed to get over the original problem Then you need to ensure you input file has no trailing lines And now to work out why I'm getting Traceback (most recent call last): File makeShapeColoured.py, line 349, in module result = voronoi.computeVoronoiDiagram(pts) File /home/kev/osm/voronoi.py, line 746, in computeVoronoiDiagram voronoi(siteList,context) File /home/kev/osm/voronoi.py, line 206, in voronoi edge = Edge.bisect(bot,newsite) File /home/kev/osm/voronoi.py, line 404, in bisect newedge.a = dx/dy ZeroDivisionError: float division ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] Postcodes to Shapefile
On 26 April 2010 15:13, Jerry Clough - OSM sk53_...@yahoo.co.uk wrote: GRASS seems to have some kind of Voronoi algorithm, but I find its interface very non-intuitive, so have not found it to try it out. This may be worth pursuing as an alternative route. As an aside: I notice that virtually all postcode boundaries are obviously created in this way. For instance the Philips Street Atlas shows totally implausible boundaries along the River Trent in S. Notts. Given that postcode boundaries are ultimately determined by logistically sensible walks for postmen, in this case it's pretty safe to assume that the boundary is actually the river. What this means is that by applying a bit of local knowledge and the existing points it is possible to create better delineating zones in OSM than appear in current mapping. Whether this is a good thing to do, or not, I leave for others to decide. I think that GEOS has now implemented both voronoi and Delaunay triangulation algorithms. I am not quite though that they have a Python Binding. Some part of GEOS is expose through the GDAL binding, but it is incomplete. Emilie Laffray ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
