Abstract: The Watershed Allied Telemetry Experimental Research (WATER) is a large scale observation experiment designed to resolve the scientific questions of earth surface system science, which includes the forest hydrology experiment located at the Dayekou ecoligical station of water source conservation forest in Qilian Mountains. The forest type is the secondary natural forests of Picea crassifolia. In order to match the data simultaneously acquired through airborne or satellite-borne observations and field-based observations, the research adopted independent observations by using the DGPS and the Total Station respectively. The Total Station observations were used as reference values, and used for analyzing and assessing the DGPS positioning accuracy in forests. The result shows that the differential process accuracy of single frequency is similar to the differential process accuracy of double frequency. The satellite number or PDOP values doesn’t reflect the positioning accuracy while the closure is the major influence factor. The positioning accuracy level varies from sub-meter to meter.

Key words: Heihe River Basin, secondary natural forests, Picea crassifolia, DGPS, Total Station