At this point, might as well just use GPS with altitude. LatLong down to 7 decimal places gets you down to a centimeter or half inch at the equator, better at h

At this point, might as well just use GPS with altitude. LatLong down to 7 decimal places gets you down to a centimeter or half inch at the equator, better at higher or lower latitutes. Add sea level to the same precision, and you can specify any cubic cm on the planet with about 27 bytes (10 each lat/lng, 7 for altitude offset from sea level at centimeters, giving you 10km of range). Specify your post office box door keyhole, or under your doormat, or in the bush by your porch... it took about as much data to describe these locations in general as to describe the exact location of one