Back azimuth is the azimuth of which direction?

• A. From A toward B
• B. From B toward A
• C. Equal to the forward azimuth
• D. Defined only on a sphere

Answer: (B)

Back azimuth is the direction pointing from the second point back toward the first. In other words, if you go from A to B along a certain line, the back azimuth is the azimuth from B to A. This is simply the opposite direction, so the back azimuth equals the forward azimuth plus 180 degrees (mod 360). For example, if the line from A to B has a forward azimuth of 30 degrees, the back azimuth from B to A is 210 degrees.

This is why the correct description is “from B toward A.” The direction from A toward B is the forward azimuth, not the back azimuth, and the back azimuth is not restricted to a sphere—it’s a general opposite direction concept.