竹林环境中GPS信号质量及其定位性能分析

Signal Quality and Positioning Accuracy of GPS under Bamboo Forest

竹林定位有助于大规模林业的智能管理,然而竹林环境的GPS定位性能一直没有被测试和评估。该文采用多接收机多测试点思路测试竹林中GPS信号质量及其定位性能,并采用全站仪提供测试点参考真值。测试结果表明:与开阔天空相比,竹林环境GPS信号载噪比平均衰减5dB-Hz,多路径误差增加一倍;典型竹林环境下GPS静态相对定位的水平定位误差小于2.5cm,且卫星几何分布对GPS定位精度影响明显。因此,这种厘米级GPS静态定位可以在竹林资源管理中发挥作用。

GPS techniques can boost forest management and inventory control.Compared to the broadleaved forest that causes serious GPS signal attenuation and multi-path,bamboo forest has distinct characteristics and has better GPS positioning.Two commercial survey-grade GPS receivers were tested in a bamboo forest,and the GNSS static relative positioning method,i.e.Post-Process Kinematic（PPK）,was used.The carrier to noise ratio and multi-path of the GPS signals were compared between open sky and bamboo forest to assess the impact of the bamboo canopy to GPS signals.The reference truth coordinates obtained by total station were used to evaluate the accuracy and precision of the PPK coordinates from the static GPS L1 and L2observations.The results show that GPS signals were affected distinctly by the bamboo forest,such as satellite signal attenuation of5 dBHz level and increased multi-path errors.Data analysis has shown that the geometry of the satellites can significantly affect the positioning results.With sufficient number of satellites and reasonable geometry,the positioning errors of GPS receivers can be less than 2.5cm in the bamboo forest.With such unexpected centimeter level positioning precision and accuracy,GPS static relative positioning can be used for bamboo forest management and inventory control.