What is "picture flying" and does the FAA define it in any of their literature?
Here is an example situation. You are instructed to depart using a SID. The SID states that at 1.5NM from ABC VORTAC a left turn should be made to heading 360. Your FMS allows you to draw a 1.5NM ring around the fix on your moving map, so you draw the line. When the little airplane is at the line, you make the turn. Anecdotally, I have been told this constitutes "picture flying" and isn't a legal way to comply with instructions from a SID or other procedure. The legal method would be to tune the VORTAC and make the turn when the DME reads 1.5NM.
One could make the argument that the DME is as inaccurate as the visual estimate from the picture flying. Aircraft climb at different rates and the angular distance affects the straight-line distance across the ground, especially if the instructions are something like, cross 20NM from ABC VORTAC at 10,000 feet.
Any definition or clarification from FAA publications or letters would be appreciated.