non-technical surveying, or the formal gathering of mine-related information, is required before actual clearance can begin. impact surveys assess the socio-economic impact of the mine contamination and help assign priorities for the clearance of particular areas. impact surveys make use of all available sources of information, including minefield records (where they exist), data about mine victims, and interviews with former combatants and local people. technical surveys then define the minefields and provide detailed maps for the clearance operations.