The UK mapping agency, the Ordnance Survey, has finally agreed to free up the vast majority of its data for public access. The OS OpenData service has launched after months of pressure from the Free Our Data campaign, started by the Guardian newspaper, which demanded that government funded and approved agencies allowed access to the tax payer.
The OS was set up not directly funded by the government but, at the same time, its job has been to gather mapping data on our behalf. The argument then runs that the public should be be able to access it for free, which, as of today, we now can.
The only downside for campaigners and, particularly ramblers, is that the decision has not made available the paper maps for free. These maps cost £15 each in the shops and are described as essentials by walking groups.
Google Maps and alike do not offer the kind of detail you can get with the full OS maps, but there are projects like the OpenStreetMap which crowd source the information for themselves rather than buying the data from the OS.