In our previous photogrammetry image capture sequences, we would take all photos horizontal and then come back at 90 degrees. When we are done capturing at 90 we go back at 270. Working on a building or stationary object with a lot of harsh shadows from the sun can be difficult. The shadows move too quickly to be shooting horizontally all the way down the wall, then coming back at 90 degrees. The software will have more difficulty recognizing points if the shadows (especially on a heavily textured wall) are completely different.
To fix this issue we shot horizontally, 90 degrees and 270 degrees all in the same spot. We used the vertical shots to overlap 60% and move 30%-40% along each frame. Doing this we knew that our horizontal shots would overlap at least 60% without a doubt. We’d be taking extra pictures horizontally, but this allowed us to move quickly along the wall before the shadows drastically changed.
If you are working with an object with rapid moving shadows, such as leaves from a tree, it would be best to manipulate the lighting conditions with an arc lamp. This will allow you to light the object from underneath so you get rid of the pesky shadows.