I’m very impressed by what the GPG3 does for the price. As an experiment, I attached a marker to one end, and did a simple loop of: (forward 15 cm, turn 90 degrees). Apparently the wheels slip a little bit on the paper so it does not draw a perfect square (this is running fairly slow, at 10% speed). The resulting drawing shows the turn wasn’t exactly 90 degrees.
Just curious: if I had the compass attachment to determine heading, could I get closer to an exact retrace, or would it still have this much drift each time around?