Property Beacons

The photo on the right shows two corner beacons on my country plot, both marking (almost) the same spot. That is not a beacon in the foreground, just a big stake which once held the corner of a fence -- not in my time. Behind it is an old property beacon -- a stake in the ground. Just to the left of that, the municipality "upgraded" the beacon, using sophisticated techniques. The new beacon is a round one, just peeping out of the ground. It is said to be accurate within 2 cm (less than an inch). OBSERVATION: The plot is in a wedge shape, of which perhaps two-thirds turns into a flood plain every so many years. This is at the thin end of the wedge. In fact the next beacon has been washed away -- in my time. There is nothing left where that one should be -- just a precipice.