Mapnik and OS_OpenData

I decided to compare the quality of OpenStreetMap mapping to that which has been released by Ordnance Survey OpenData.  
I started with VectorMapDistrict, which is a dataset provided as ESRI Shapefiles.   It is provided as a large number of shapefiles, so setting up a mapnik stylesheet manually would have been a pain.  Instead I separated the styles into an XML file, but added the layers using a python program which scans down the directory tree to add the various shapefiles to the map.  The python code is vmdmap.py and the stylesheet is styles.xml.

Then I tried Meridian2.  This is much simpler - just one shapefile for each sort of feature (A-Road, river etc.).  I kept the same structure with the styles defined in an XML file, and the layers in python, but it could have all been done in a single XML file this time.  The python code is md2map.py and the stylesheet is styles_md2.xml.

You can see the results below.

The most notable things are that Meridian2 is much simpler geometry, but it includes more road names than Vector Map District.  The OpenStreetMap rendering is fancier because I used the standard OSM style, rather than the home made ones I used for the OS Data.   I do like the rocks that appear in the VectorMap District rendering though - I will have to import it into OSM!.

VectorMapDistrict

Meridian2

OpenStreetMap

Mapnik and OS_OpenData

I decided to compare the quality of OpenStreetMap mapping to that which has been released by Ordnance Survey OpenData.  
I started with VectorMapDistrict, which is a dataset provided as ESRI Shapefiles.   It is provided as a large number of shapefiles, so setting up a mapnik stylesheet manually would have been a pain.  Instead I separated the styles into an XML file, but added the layers using a python program which scans down the directory tree to add the various shapefiles to the map.  The python code is vmdmap.py and the stylesheet is styles.xml.

Then I tried Meridian2.  This is much simpler - just one shapefile for each sort of feature (A-Road, river etc.).  I kept the same structure with the styles defined in an XML file, and the layers in python, but it could have all been done in a single XML file this time.  The python code is md2map.py and the stylesheet is styles_md2.xml.

You can see the results below.

The most notable things are that Meridian2 is much simpler geometry, but it includes more road names than Vector Map District.  The OpenStreetMap rendering is fancier because I used the standard OSM style, rather than the home made ones I used for the OS Data.   I do like the rocks that appear in the VectorMap District rendering though - I will have to import it into OSM!.

VectorMapDistrict

Meridian2

OpenStreetMap

Mapping - OSM and Mapnik

I have been playing with mapnik quite a bit lately - I decided I needed to learn how to use it better to improve my townguide program.
I have been very impressed with Lonvia's Hiking Map, which is an overlay showing hiking routes on top of a standard OpenStreetMap map, and thought I could do something similar.

My first effort was a map showing the locations of supermarkets (handy when we go on holiday so we know where to go to stock up on provisions) - It can be seen here.
Someone has imported a lot of powerline data from Ordnance Survey into my local area, so I tried a Power Station Map.  These maps all have an 'about' link showing how they work.

I have produced a similar one to show the use of Ordnance Survey OpenData in the OpenStreetMap map of the UK, which can be seen here.

More recently I have wanted to produce maps that include contours, and also allow me to plot GPX traces to show where we have been.   To do this I have imported the SRTM data for the UK into my postgresql database using the technique described here.   This allows me to render an Openstreetmap map with contours, which is useful for the countryside.

Adding a GPX trace over the top was a bit difficult - I wanted to do it in python to save hard coding the path to the GPX file in the mapnik style file, but I haven't managed to do that - I ended up adding a GPX layer to my mapnik style file using the mapnik ogr plugin.   The result can be seen here.

Mapping - OSM and Mapnik

I have been playing with mapnik quite a bit lately - I decided I needed to learn how to use it better to improve my townguide program.
I have been very impressed with Lonvia's Hiking Map, which is an overlay showing hiking routes on top of a standard OpenStreetMap map, and thought I could do something similar.

My first effort was a map showing the locations of supermarkets (handy when we go on holiday so we know where to go to stock up on provisions) - It can be seen here.
Someone has imported a lot of powerline data from Ordnance Survey into my local area, so I tried a Power Station Map.  These maps all have an 'about' link showing how they work.

I have produced a similar one to show the use of Ordnance Survey OpenData in the OpenStreetMap map of the UK, which can be seen here.

More recently I have wanted to produce maps that include contours, and also allow me to plot GPX traces to show where we have been.   To do this I have imported the SRTM data for the UK into my postgresql database using the technique described here.   This allows me to render an Openstreetmap map with contours, which is useful for the countryside.

Adding a GPX trace over the top was a bit difficult - I wanted to do it in python to save hard coding the path to the GPX file in the mapnik style file, but I haven't managed to do that - I ended up adding a GPX layer to my mapnik style file using the mapnik ogr plugin.   The result can be seen here.

The Irritating thing about Android

I have recently got an Android phone so that I can write software for it without the irritating security issues you get with J2ME on 'normal' phones (boxes popping up saying 'do you want to let this program do this?' etc.).

I was very surprised that some things that most phones do 'out of the box' are a real pain in Android, that makes me think this is still a platform for gadget enthusiasts rather than end users.

These include:

* Sharing Contacts: All of the phones I have seen with bluetooth let you send contacts from one phone to another over bluetooth. Not Android - I ended up adding my contacts from my old phone to Google Mail manually. This made them appear on the Android one.
* Using the phone as a modem: My Sony Ericsson W890i just works - plug the phone into a computer and it appears as an ethernet card - dead easy (I think I had to select this as an option in the phone menu, but it was just a simple menu action. The nearest thing I have got with Android is a program called 'Proxoid' to run on the phone. You then have to use the ADB program that comes with the Android Developers SDK to forward packets to the phone, and set up your browser to use a proxy. A long way from an end user experience. I'll do a separate post on this so I can remember how to do it next time I am stranded in Spain and my T-Mobile broadband dongle won't work!

Reprojecting Ordnance Survey Raster Data

I have been looking at the Ordnance Survey StreetView data that was released to the public on 1st April.
This has got me thinking about a previous project that I failed to make work - I have some old maps of my home town and wanted to be able to display them on the web and switch between them so you can see what changes from year to year - I have maps from 1870 and 1914.  I want to use OpenStreetMap as the recent data.  Now StreetView is available I can use that too for comparison.

The problem is projecting them onto the same coordinate system - I failed miserably last time, but my two scanned old maps were on the same scale, so you can see them at (http://maps.webhop.net/oldmaps/openlayers.html).

The maps are in Ordnance Survey projection, which has the code EPSG:27700.   The downloaded OS data has the origin specified in metres northings and eastings.
You can translate this into the same projection as OpenStreetMap (EPSG:900113) using:

gdalwarp -s_srs EPSG:27700 -t_srs EPSG:900913 *.TIF nz.tif

Check the projection information with

gdalinfo nz.tif | more

Ordnance Survey Data Released

Ordnance Survey have released quite a lot of data for free use (http://www.ordnancesurvey.co.uk/oswebsite/opendata/).
The most interesting sounding data (meridian) is a 2Gb shape file, so I chickened out of trying to do anything with that tonight.
Instead I downloaded the 50k Gazetteer and have put it into a postgresql database so it can be queried to look for things.
Work in progress is at http://www.maps2.webhop.net/openos.
It sort of works (just not very useful yet - you can do http://maps2.webhop.net/openos/gaz/www/doSearch.php, and it gives you a list of all of the items in the database containing the string 'hartlepool' - just need to transfer them back to the browser and plot them on a map now....