DGPS在资源环境遥感中的应用方法研究

Research on DGPS Method in the Field of Resources and Environment Remote Sensing

为了能够利用较低配置的GPS设备 ,方便有效地完成与资源环境遥感有关的地物定位测量任务 ,利用伪距DGPS设备进行了如下试验研究 :基站参考坐标对定位精度的影响、基于大地测量三角控制点和WGS84到北京 5 4坐标系转换模型进行基站参考坐标差分测量导算的方法和精度、在导算出的控制点处建立基站进行试验区样地定位测量的方法及所能达到的精度。试验结果表明 ,在具备测区至少一个三角控制点和坐标转换参数条件下 ,可以采用首先从已知三角点导算出一个位于方便位置处的点的大地坐标 ,然后在该点建立基站用于完成实际测量任务的方法。以遥感影像作为参照对其绝对定位精度进行了评价 ,发现这种方法所能达到的在当地坐标系中的相对定位精度远远小于一个像元大小 ,可以推广应用到资源环境遥感的各个应用领域。在不具备基站参考坐标和坐标系转换参数的条件下 ,可以基于差分测量结果之图形要素绝对位置精度高且不随基站地心参考坐标小量变化而改变的特点 ,采用图形到遥感影像配准的方法直接将测量结果图形转换到已经和当地坐标系配准的遥感影像上去。采用这种办法 ,在差分处理时不用考虑基站的精确WGS84地心参考坐标 ,也不用考虑坐标系的转换参数 ,利用基站单点绝对定位结果作为参考坐标进行差分就可 。

In order to efficiently and accurately measure geographic locations of ground truth features in the field of resource and environment remote sensing using economical and easy operational GPS instrument, the following experiments were carried out using C/A code pseudo_distance differential GPS instrument (DGPS). Firstly, the effect of base station's geo_center reference coordinate (WGS84) on location accuracy was evaluated. Secondly, a point was differentially located with a known trigonal control point as base station site and a three parameter Molodensky Model as datum transformation model between WGS84 and Beijing 54. On this point, we then established a temporal base station, which was used to measure the aimed ground truth features in the test site. The location accuracy attained by this route was evaluated as well. It was found that DGPS measured map is of highly absolute accuracy (2\_5m), and this absolute accuracy does not change with the minor error of geo_reference coordinate of the base station. It is a practical method to measure and establish a new temporal base station, which can be used to carry out the real measure work in the test site. The location error of this method is far under one image pixel size (25m) with one geo_referenced TM image as evaluation reference. However, if the trigonal control point and datum transformation model do not exist, the result of base station single point absolute location can be used as reference coordinate, the measured result of which can be geo_referenced to remote sensing image using some tiepoints on the basis of the first result above. Because this method does not need to know the geo_reference coordinate and datum transformation model, it's a ecnomical and practical method for resources and environment remote sensing.