TELEVISION?S Map Man Nicholas Crane homes in on Dartmoor for the sixth programme in his series on the mapping of Britain. Crane undertakes a coast to coast walk of Devon, using a map drawn up almost 200 years ago as part of preparations for a Napoleonic invasion of Britain. The map was the work of Devonian Lt Col William Mudge and was the first edition of the Ordnance Survey. Presenter Crane, whose BBC2 Map Man programmes have been retracing the routes of old maps, finds Mudge?s survey still accurate, despite changes in the landscape since 1809. But when he steps into the wilderness of Dartmoor, following Mudge?s map at times proves difficult because of the lack of clearly discernible features. On the north moor, he receives advice from Okehampton Camp commander Col Tony Clark and manages to follow the map across the bleak landscape to Cranmere Pool. Today?s Ordnance Survey maps are a direct descendent of those created by Mudge. The Map Man programme featuring Dartmoor is on BBC2 at 8pm on Monday October 10.