Since 1st April 2010, Ordnance Survey has released a large amount of their map data under a free licence. The maps that this app uses were all included in this data. For more information, see the OS OpenData website.
Specifically, this app includes the OS MiniScale®, 1:250,000 scale colour raster, OS VectorMap™ District and OS Street View® maps. The app's search feature uses the 1:50,000 scale gazetteer, the OS Locator™ street index, and the Code-Point® Open postcode data.
None of the 1:50,000 Landranger® or 1:25,000 Explorer® data has been released, so this is not included in this app. However, 1:50,000 contour data ("OS Terrain 50") has been released, and is used to superimpose contour lines over the detailed maps. The contour interval is 10m, with index contours every 50m.
The Terrain 50 data is also used to implement the hill shading features. For this purpose the gridded version of the data is used, with a horizontal resolution of 50m. You can see this resolution as a blocky effect when zoomed in on steep ground. The altitude display is interpolated from this data, so will not be perfectly accurate for things like summit heights.
None of the OS data released so far includes footpaths. Since footpaths are essential for countryside use, this app has superimposed footpaths derived from openstreetmap.org data. These paths have been recorded by volunteers; coverage is not yet complete and varies from place to place.
The OS OpenData licence allows commercial use of the data provided that the source of the data is acknowledged and the same rights and obligations are passed on to users of the derived product. Please see the licence for details.
In editions 4 and earlier of the maps, the OpenStreetMap data was licensed under Creative Commons Attribution-ShareAlike 2.0 terms. Since edition 5, the OpenStreetMap data is licensed under the Open Database License v1.0, under the terms of which these maps are a produced work. We would be happy to provide a copy of the derived database used in the production, or the algorithm used to create it, as required by sectin 4.6 of the licence; please contact us by email.
You are therefore free to use maps from this app (e.g. screenshots or similar) for any purpose, provided that you acknowledge Ordnance Survey and OpenStreetMap as the source of the maps and pass on the same terms.