Consider the following:
(i) Line ranger
(ii) Reciprocal Ranging
(iii) Random line ranging
(iv) Optical square
Which of these are employed to solve the problem of vision obstructed but chaining free?1
(i), (ii), (iii) and (iv)
2
(ii) and (iii) only
3
(ii) and (iv) only
4
(iii) and (iv) only