No flight lines in Tower survey mission

[Ketch]

i believe that it comes from the 3d world. in 3d you can draw a polygon and fill it with pattern, solid color or gradient. in tower, you draw a polygon around the region to survey and tower automatically fills it with a hatching pattern which is the optimal flight path. the angle is relative to the xy plane.

Franknitty, I did a little research and you are right, it refers to a hatch or hatching, and I guess you can consider the parallel flight lines as a hatch, thanks for your input.