As a result of the hydrologic and erosion processes

rock fragment is a sign of soil and ecosystems degradation

which in turn affects erosion processes.The purpose of this study is to investigate the precision differences between sampling and photographic methods in rock fragment covers measurements.To do this

rock fragment covers with different particle sizes(2~6mm

6~20mm and 20~60mm)were measured by these two methods.The results showed that both sampling and photographic methods can be used to measure the rock fragment cover effectively.The relative errors measured by two methods varied by-7.84%~80.86%and-48.35%~9.89%

respectively.The mean relative error of these two methods was 15.69% and-11.69%

respectively.The relative error measured by sampling method decreased with the increasing of rock fragment cover.The maximum absolute relative error measured by sampling method reduced with the number of sampling

but this trend became gentle when the number of sampling was up to about 30.