I went outside to practice mapping a trail using just dead reckoning. It's a lot tougher than it looks. Just getting a good bearing is difficult with the glare on the compass. It would be better to have a tape measure for those legs that are curved a lot. I used Excel to plot the vectors as it's just easier. With a lot of care and 40 minutes I came out dead on for 700 feet.

Then the compass was pointing 90 degrees off on the corner. Something is there. Aliens maybe? More likely some electrical field.