林冠开阔度对GNSSRTK在森林中定位可用性及初始化时间的影响  

Effects of Canopy Openness on Positioning Availability and Initialization Time of GNSS RTK in Forests

作　　者：李永宁[1] 刘利民[2] 崔立艳 黄龙生[1] 赵中凯[1] 黄选瑞[1] 

机构地区：[1]河北农业大学林学院,保定071000 [2]河北省木兰围场国有林场管理局,围场068450

出　　处：《林业科学》2014年第2期78-84,共7页Scientia Silvae Sinicae

基　　金："十二五"农村领域国家科技计划"华北土石山区森林可持续经营技术研究与示范"(2012BAD22B0304)

摘　　要：RTK是高精度的实时卫星定位技术,但由于林冠对信号的遮挡,GPS RTK技术在林下很少应用,而采用双星定位系统的GNSS RTK则有较为广阔的应用前景。以冀北山地杨桦次生林为例,采用GPS+GLONASS双星系统进行RTK定位,通过全天空照片测定林冠开阔度,探讨林冠开阔度对GNSS RTK定位可用性及初始化时间的影响。结果表明:全天空照片能较好地描绘GNSS定位的森林环境,且卫星多位于中等高度角,林冠开阔度是反映森林中定位环境条件的适合指标。采用双星GNSS系统,有足够的卫星数满足定位要求,林冠开阔度与共用卫星数呈显著的线性正相关关系;92.3%的PDOP值小于4,卫星有良好的空间几何分布;森林环境对信噪比有较大影响,信噪比与开阔度呈显著的正相关关系。林冠开阔度在0.25以上时,反映定位可用性的各指标均较好。随着林冠开阔度增大,RTK定位所需的平均初始化时间变短。从观测时间长短与测量效率分析,15 min是适宜的时间限值。Though RTK is a satellite positioning technology with high precision, GPS RTK technology is sehlom used in forests due to the obstruction of forest canopy to the satellite signal. GNSS RTK with two satellite systems has broad application prospects. The effects of canopy openness on positioning availability and initialization time of GNSS RTK were studied in secondary poplar-birch forests in mountain land in north Hebei, positioning with GPS ＋ GLON ASS RTK system, measuring forest canopy openness with hemispherical photograph. The results showed that canopy openness was the most fitting indicator, since hemispherical photograph could represent well forest environment and most satellite had medium elevation angle. Satellite number was enough to meet the positioning requirements. Forest canopy openness had significant positive correlation with common satellite numbers. PDOP value more than 92.4% was less than 4, and there was a good satellite geometric distribution. SNR was significantly positively correlated to canopy openness, and was affected greatly by forest environment. All indicator of positioning availability were good when canopy openness was more than 0.25. Average initialization time of RTK was becoming shorter with the increasing canopy openness. The suitable occupation time was 15 min with regard to surveying duration and surveying efficiency.

关 键 词：RTK 林冠开阔度 全球卫星导航系统 信噪比 初始化时间 PDOP 

分 类 号：S757[农业科学—森林经理学]