Mapping agency Ordnance Survey (OS) has launched a service offering free and unrestricted access to most of its map data.
After months of public consultation, OS OpenData was launched on 1 April by Communities Secretary John Denham.
He said he hoped it would attract "a new wave of entrepreneurs" to reuse the data in innovative ways.
However Ramblers, the walkers group, has expressed disappointment that OS' paper maps have not been included.
"We are very disappointed that the walkers maps have been left out of it," said a spokesperson from the group.
The group had lobbied for the inclusion of the paper map ranges - called Explorer and Landranger - during the consultation, he added.
The maps retail for up to £15 in shops and walkers describe them as essential guides. http://news.bbc.co.uk/1/hi/technology/8597779.stm