Today a user posed a question that had me scratching my head just a bit, but only because I couldn’t make the solution in my mind match the output on the screen. His issue: he has a boundary survey, and had to rotate the drawing by a certain angle, but wants to label the linework by the original angle. If that is as clear as mud, let’s say that he has a baseline drawn at N0°E and has to rotate it 2° to the right, but still wants to label with the original bearing of N0°E rather than the actual direction of N2°E. Follow the link to see my solution.

I initially knew that the answer was an expression, and the thought in my head was “wow, this is easy.” However, after creating the expression, I became acutely aware that something was wrong…I wanted to rotate my drawing 2° to the right, and my test line drawn at N90°E came back much closer to S24°E. Now, I’m pretty good at math, and I can definitely tell that 90-2 does not equal 24. So, back to the drawing board (no pun intended – ok, pun TOTALLY intended!)

The expression that I was using was {General Segment Direction}+2. I tried editing ambient settings and nothing happened. I tried entering 0.02 just to see what happened and I got much closer to the desired number. The result was so close that I realized that it was a units issue.

On a hunch, I changed the expression – I entered {General Segment Direction}+DEG2RAD(2)…converting my 2° to radians. BINGO! It worked! As it turns out, ambient settings aside, the Expression Editor is looking for radians, not degrees. With that conversion factor in the expression, it works perfectly!

This process can be used to add a rotation angle to all bearings or subtract a rotation angle from all bearings, depending on the direction of rotation. It should be done on a project-by-project basis and not in a drawing template, as rotation angles will vary from drawing to drawing.