距离及高程测量是要测出各桩位间的水平距离以及它们之间的高差。当采用视距法测量时,在平地时应不超过(____);在丘陵地带应不超过(____);在山区应不超过(____),当透视条件不好时,还应适当减少视距长度或停止观测。
A400m,500m,600m
B500m,600m,800m
C400m,600m,700m
D400m,600m,800m
A400m,500m,600m
B500m,600m,800m
C400m,600m,700m
D400m,600m,800m