I'm convinced the average person cannot see in 3 dimensions when they look across the water. They can recognize right and left, and to some minor extent distance, but they cannot accuratly relate what they see to a map-view.
Anchoring is the classic case. They move the boat to what seems like a good spot and lower the anchor, without being able to visualize where the boat will be after they stretch out scope, or how boats may swing. They end up anchoring either very close in front of you or exactly beside you, neither of which they actually intended. They just measured wrong.
- Calculate how much rode you will use, including an allowance for adding scope if a storm arrives. For example, if the water is 7 feet, you bow is 3 feet, and you like 7:1 scope, (7+3) x 7 = 70 feet.
- Lower your anchor 1 rode length +1 boat length off the bow of your neighbor. This might be 1.5 to 2 mast-heights, a simple way to gauge distance if you are reproaching from astern of your neighbor. By the time the anchor tips, digs, and sets, particularly in softer mud, it will be off the beam of your neighbor.
- Need to anchor in front? You need to be about 2 rode lengths + 2 boat lengths (about 210 feet). Simple come up beside the boat, note the lon/lat, and move 0.039 minutes forward (a minute is 1 nautical mile, and GPS typically displays 0.001 increments). Or time the distance; 1-knot ~ 1.5 feet per second. At 3 knots, 210 feet will take about 45 seconds. The point is, do something better than just guess.
Simple.This, along with every detail of single and multi-anchor rigging that I could test, is described in "Rigging Modern Anchors."