Wikipedia says a bit: “GPS Drawing combines art, travelling (walking, flying and driving) and technology and is a method of drawing that uses GPS to create large-scale artwork.”
About the project:
“On 25th May 2004, fifty bottles containing messages were released into the sea off the south-east coast of England near Ramsgate Maritime Museum, Kent. The intended destination of the bottles is The Chatham Islands in the South Pacific Ocean. The islands, which are 800km east of mainland New Zealand, are the nearest inhabited land to the precise location on the opposite side of the world to Ramsgate Maritime Museum. It is anticipated that the bottles may be found several times before reaching the Chatham Islands.
Several of the bottles are being tracked using GPS technology and are programmed to send their longitude and latitude coordinates back to Ramsgate every hour. The information they transmit is used to create a real time drawing of their progress.”