Measures accessibility - the average effort required to reach the feature. Each feature was sampled at points every 15m, and a cost surface was generated for a 1/2 km circumference around each point using effort as the friction surface. These cost surfaces were then summed and averaged. "Effort" was derived by augmenting the slope values for the sample area based upon the equation developed by Bell and Lock (2000).

Bell, T. and Lock, G. (2000.) 'Topographic and cultural influences on walking the Ridegway in later prehistoric times', in G. Lock, ed., Beyond the map: archaeology and spatial technologies (Amsterdam-Washington, DC): 85-100