SPOT – The First Satellite Messenger

by P/R/C Don Hagen, SN, Radio-Tech Officer

My March 2007 column described EPIRBs(Emergency Position Indicating Radio Beacons) and Personel Locator Beacons (PLBs). Last year a personal tracking device called SPOT was introduced. It operates similarly to a GPS-enabled PLB, with some important differences^1.

SPOT sends your GPS coordinates and selected messages over commercial satellites to inform others of your location and status. It features four key functions that enable users to send messages to friends, family, or emergency responders, based upon the level of need:

SPOT, Inc. is owned by Globalstar and uses the Globalstar satellite network (described in my June 2007 column). Globalstar has a constellation of 48 satellites in a 900-mile orbit. These use the "bent-pipe" method for routing signals up to and down from a single satellite: The satellite must be in view of the SPOT tracker as well as a Globalstar ground station. This mutual view requirement allows nearly global coverage, including North and South America, hundreds of miles out to sea along the U.S. West Coast, the Caribbean, the north Atlantic, and many countries in Europe. However, many open ocean areas and much of the Southern Hemisphere are not covered, so if you're traveling to those places, an EPIRB or PLB would be necessary.

The SPOT tracker costs about $150 (compared to $500-600 for a PLB or $900-1200 for an EPIRB). However, it requires an annual subscription fee of $100 for basic services, and an additional $50 for the automatic tracker service. A $100,000 Rescue Plan costs $8 per year, and covers extrication by helicopter or other means in a disaster if there is no local rescue agency nearby, which sounds like a good idea for a foreign ocean voyage² EPIRBs and PLBs, of course, have no subscription fee, but can be activated legally only in an emergency. There is no "I'm OK" or routine tracking service.

The unit is powered by two AA lithium batteries. These can provide tracking for 14 days, 911- mode for 7 days, or 1900 check-in messages. User comments indicate that the SPOT GPS receiver is not as sensitive as most modern handhelds, and requires unobstructed line-of-sight to the sky to work properly. This would be a handicap for use in hiking in even moderate tree cover, but is probably all right for vessels at sea. Another complaint is that there is no way to tell whether a message was successfully transmitted³

^1.2008 West Marine Catalog, page 33.
^2.Gordon West, “On the Spot,” Marine Electronics, Nov/Dec 2008, page 34.
^3.“SPOT Satellite Messenger Personal Tracker Review,” GPS Magazine, Jan 23, 2008.