I am no expert on this heck I dont even own one yet but will. I am just guessing here but, is it because there are two different distances here. Well I dont know how to say what I want. One being the depth is straight down and the other measurements are to the left and right or horziantal arcoss the water. Meaning that the Buildng is 75 feet to the right of the boat, so a person needs to go that distance and then go down with the depth reading. If that is the case you wouldnt really be able to read the graph literally and just make take it that the SI adjusted the image.

Or maybe I am totally wrong and the building is 75 feet from the boat at a direct line from the boat at an angle.

Heck I dont know, I am just reading up on these because I will have one before spring and what to have some Idea on how it works and how to read it.

Thanks
Clint