More Rigorous Correction of Refraction Effects in Two-media Stereophoto-grammetry

A more rigorous algorithm is presented for correction of refraction effects in two-media stereo photogrammetry. The mid-point of the shortest line segment joining two aerial corresponding rays of a point on an underwater object is used as a photogrammetric intersection point which doesn't exist when the two rays are non-intersecting. As a result, the uncertainty of the intersection point is removed, the positional relationship between the intersection point and the true object point becomes definite, and the refraction correction formula from the intersection point to the true object point can be strictly derived. The bad effect on the refraction correction is firstly analyzed, which caused by that the two rays are non-intersecting. Then the positional relationship between the intersection point and the true object point is studied. After that, the formulas regarding water depth and geodetic coordinates of points on an underwater object are deduced, that is often known as correction of refraction effects. Finally, the algorithm is tested by two experiments using the data of WorldView-2. The results show that the algorithm is suitable for any case in which whether or not the two aerial corresponding rays of an underwater object point are intersecting, and it can significantly improve the measurement accuracy of underwater object's elevation