I never thought I'd see this: Open Map Data from the Ordnance Survey

Ordnance Survey have always been quite protective of their data. Whatever the political and economic arguments for and against this, it's not really affected my work, as I've always had access to OS data through working in academic institutions or as a consultant on government agency projects. But what happens now I'm trying to work independently?

Last year OS released a number of free digital map products, and I've only just caught up with them. I've only had a look at two raster products so far - VectorMap District and OS Street View, which have nominal scales of 1:25k and 1:10k. Other products at smaller scales are also available.

OS have "generalised and simplified" these products to "allow you to easily visualise a variety of information in its geographic context". So they provide a simple background for other spatial data, uncluttered with unnecessary information. This also means that OS can still charge for their fully detailed products. The products are licensed for any use, as long as OS is attributed (licence here).

Data is supplied from the download page via an emailed link, and comes in 10x10km or 5x5km tiles. This can mean a lot of tiles: 400 tiles for one 100x100km national grid reference square of Street View for example. I've used QGIS's excellent VRT functionality to look at many tiles without building an overly cumbersome single raster image - you'll need the gdal plugin to use this.

OS VectorMap District map of Seascale, Cumbria. Contains Ordnance Survey data © Crown copyright and database right 2011.

OS Street View map of Seascale, Cumbria. Contains Ordnance Survey data © Crown copyright and database right 2011.

How does it look? It's OK - fairly uncluttered, reasonably clear. It's not up to the elegance of the full 25k or 50k OS maps, but fine for a backdrop to other data for websites and reports. I think it fulfills the aim of providing adequate context for other spatial data, but you couldn't use these for planning a walk for example - there's no right of way information.

OpenStreetMap using Osmarender. © OpenStreetMap contributors, CC-BY-SA.

I think it looks better than OpenStreetMap or GoogleMaps for web based stuff, and because it's downloadable as tiff it's better for use in "serious" GIS applications.
One problem with the VectorMap data - it's supplied as a tiff (but not GeoTiff - so no spatial reference system information), with a colour table with low saturation colours. I don't like this - the colours look washed out, and while this is OK for some background mapping, I prefer to set the background appearence myself, using transparency.

OS VectorMap District map with colour saturation increased with a factor of 75%. Contains Ordnance Survey data © Crown copyright and database right 2011.

There's a fairly simple fix for this, by building your own colour table, which can the be loaded into QGIS. I've made a couple of spreadsheets to help me do this in Gnumeric and Excel formats (downloadable here and here). You'll need to save the colour table from QGIS, paste into columns A-F in the first sheet, and select a "Saturation Factor". "1" produces fully saturated colours, "0" has no effect. 0.75 works pretty well. The adjusted colour table can then be saved as a CSV from the second sheet, and loaded into QGIS.
Useable colour tables can be downloaded here: 25%, 50%, 65%, 75%.
I'll be having a look at the vector data too - and will post again with the results.