山区调绘航片有效作业面积探讨

垂直航空摄影像片上存在的投影差,使得坡向向像主点的坡长影像相对延长,逆像主点的坡长影像相对缩短,这在高差大、坡向变化频繁的山区更为显著。当坡长影像长度小子于其理论影像长度的2/3时,坡面上的各地类界线难以判清;小于1/2时,则坡面上的许多地类都难以判出。因此,以像主点为中心的航片最适有效作业半径r_1≤- H_A/2h D_1=f/3tgα,极限有效作业半径rm=- H_A/h D_1=f/2tgα,即最适和极限有效作业半径决定于逆向坡高差h的负值和坡长影像长度D_1或地面倾角α。

DISCUSSION OF EFFECTIVE WORKING AREA OF MOUNTAINOUS AEROPHOTO FOR SURVEY AND MAPPING

It often happens that projection error in the vertical aerophoto makes the slope length toward the point image in middle longer and the contary shorter in the area of great different elevation and frequetly changing directions of slopes. When the slope length on aerophoto is less than 2/3 theory length, it is difficulty to interpret the land types clearly. The boundaries of many land types can not be intrepreted as it is shorter than 1/2 theory length. So the optium effective working radius on the aerophoto is equal to or less than - HA/2h D_1 or f/3tgα The limited working radisu is equal to - HA/h D_1 or f/2tgα. Here are the ground elevation difference of contary slope(h), the slope length in the areophoto (D_1) or horizontal tip(α).