[zardaxian]

Not much. A floating GPS antenna on a self tensioner, tablet in a housing. And some buggy code :) Good enough for swim lane mapping and preventing holidays (unsearched areas). Another system we worked with used ultrasonic positioning from beacons, very accurate and covert.

[tclancy]

Great story and it made me realize that usage of "holiday" is more general than how I thought of it (missing a spot when painting). Which led me to http://www.word-detective.com/2010/12/holiday/