An analysis of height precision in applying single frequency static GPS to landslide monitoring

As we all know,GPS has brought great convenience to surveying and mapping work. Its horizontal accuracy has reached sub- millimeter. However,due to the influences of such factors as the effects of ionosphere,multipath effect,GDOP( geometric dilution of precision) and height of antenna,the vertical deformation measurements from GPS are seldomly used by precision survey workers. Based on the reasonable layout of deformation monitoring network of Shuping landslide in the Three Gorges Reservoir Area,the authors obtained a large number of leveling and GPS data from long- term monitoring,and used leveling data as the reference to analyze the height precision of single- frequency static GPS in landslide vertical deformation monitoring. The results show that the vertical deformation monitoring precision of single- frequency static GPS is ± 2cm,that the deformation monitoring accuracy should be greater than 1 /5 of deformation in the measurement period according to the monitoring code of landslide,and that single frequency static GPS is suitable for the landslide whose vertical deformation is above 10 cm in its monitoring period. For the Shuping landslide,GPS measurement can provide good monitoring data in the second to third period whose vertical deformation is up to 30 cm,but it is unsuitable for other monitoring periods in slow state.