DGPS is no longer simply a navigation technique - it is a means to measure positions and movement of any kind to a high degree of accuracy. In the marine environment, the output from a suitable DGPS receiver could form the position sensor input to an Integrated Navigation System (INS), an Electronic Chart System (ECS) or an Automatic Identification System (AIS). In these applications the inherent integrity checking, high accuracy and stability of the differential system are particularly important. In positioning mode, DGPS is used for buoy-laying and hydrographic surveying. DGPS may also be used, often in combination with other systems, for a variety of other marine applications such as dynamic positioning, rig moves, pipe-laying, cable-laying and dredging.