GLOBAL POSITIONING SYSTEM - AN EFFECTIVE WAY TO MAP A SMALL-AREA OR CATCHMENT

The Global Positioning System (GPS) is an established method for estab lishing high accuracy horizontal and vertical control points over larg e areas. Recent improvements in receiver technology, differential surv eying and software have made the use of GPS technology more practical for smaller projects. This paper compares different GPS methods with o ccupation times of 2s, 2 min and 12 min using an existing control netw ork, and the gathering of topographic data from a difficult field site . Two examples are given, one in East Texas, demonstrating the speed a nd accuracy of different techniques, and the other in the Quantock Hil ls in Somerset.