卫星影象上专题类型转绘方法的分析

THE METHOD OF BOUNDARY TRANSFORMATION OFTHEMATIC TYPE ON LANDSAT IMAGE

对资源环境影象信息进行解译，最终要转换为不同类型的线划界线或图纹符号。计算机兼容磁带的图象处理，现在还难以对任何专题类型都能分类和转换成界线。因此，广泛应用的粗制卫星象片作信息解释后，还必须解决类型界线向地理底图正确转绘。本文着重分析按不同精度的影象图上类型界线转换问题。并提出，由于地理底图是经过制图综合的，它的点位精度比纠正后的影象图形精度低，转绘的最后步骤应是手工的地理相关转绘。

: In our country, most of thermatic mapping using Landsat image were interpreted visually. The products of interpre tation need to be transmitted to type boundary. It suggests the problem how by using bulk process image to do geornetric corrccting and transferring. Under the condition in shortage of CCT, the geometric correcting, the mixed process using computer-optical equipment is an available method. The present paper analyzed the re- sults of geometric correcting of positive or negative film on the OR-1 ortho-rectifier. The conclusion shows that it can reach such precision that the error is just 1-2 pixel. But the density of horizontal section and the density of vertical section in measured area have a great inference on precision. If the height varies greatly or the density of stream network is big, the error on corrected images is big either. The geometric correcting can also be done after interpretation-affine transform the uncor- rected type boundary. Many articles and the present paper show that, the lateral deformation is 1.4-2.3 times more than vertical one. Thus, optical-mechanical affine transformation beco- mes the major method of geometric transformation which makes the precision a lower lower. It also can be done by Zoom Transfer Scope or professional duplicator which has capability of compressing in X and Y direction. The location error of this method is about 0.4 mm From the view of mapping, the geographic precision on middle scale image is higher than that on geographical base map through many times of scale generalization. So, the type bound- ary interpreted from Landsat image, when thansferred to the base map, cannot coincide properly with geographic elements. The roots of error lie in the errors of base map. So, when transferr- ing the thematic type boundary to the base map, it is necessary to transfer, the geographic corre- lation according to the stream network on map.