集思宝G330手持全球定位系统接收机在林区单点定位的精度分析

通过三维激光扫描技术得到的树木枝干点云数据，不仅数据量大，而且特征复杂，不适合采用传统的方法提取等值线。对此，首先把点云数据中树木的枝和干分为不同的部分，然后建立点云的分层模型，并分析点云在树高方向上的数据量分布。在高精度采样下，将分层点云作为等值线的采样数据，对每层数据中不同部分的树木枝干点云分别采用凸包算法进行连接，建立树木枝干的等值线模型。结果表明:在没有先验等值线知识和建立点云对象模型的条件下，利用迭代的凸包算法可以有效地对树木枝干离散点云数据进行连接，得到的等值线符合一般等值线的特点。最后通过实例验证了方法的适用性。图8表1参11

Analysis of single-point positioning precision in forestry using a G330 handheld GPS receiver

In a forested area of Mount Tianmu，the precision of single point positioning with a G330 handheld GPS receiver compared to an observed value by GPS-RTK（Real Time Kinematic） was analyzed and evaluated. Results showed that（1） for BJ54 planimetric coordinates，inner precision with 90.0% of the test points was less than 4.0 m，but for the vertical coordinates, precision was about 85.0% in less than 6 m.（2）Also，for BJ54 planimetric coordinates, the outside precision with 85.0%-90.0% of the points was less than 5.0 m，but for the vertical coordinates，precision of was about 87.2% in less than 10.0 m.（3）For a handheld GPS receiver with no coordinate conversion parameters，when systematic deviation was eliminated，the observation accuracy of single point positioning improved.（4）Additionally，single point positioning precision could be improved through simultaneous observation using two or more handheld GPS receivers.［Ch，7 fig. 1 tab. 16 ref.］