Opinions on perpendicular (key) flight lines

[smescarzaga]

Hi folks,

I'm working with a group now who conducts manned, fixed-wing SfM missions for coastal regions. This means AOIs tend to be thin and oblong, although not quite like corridor mapping. The current operation procedure stresses the collection of images in 1-3 flight lines perpendicular the main flight lines. Conceptually, I can understand how that might strengthen the geometry of the model during reconstruction.

However, I've yet to find anything in the literature that recommends this as a procedure for airborne SfM. Furthermore, this publication (https://www.sciencedirect.com/science/article/pii/S0924271618302727#t0005) seems to suggest that they received better results without the use of this perpendicular flight line.

What is the opinion of those in this forum? This is simply just not a hard and fast rule? Do perpendicular flight lines only help strengthen the model in corridor-like surveys? Can you point me to anything on this subject in the literature?

Thank you!
Stephen