As a recent purchaser of a Magellan Pathfinder GPS system for acartographically challenged wife, and having read much about the comingadvances in GPS applications, I was eager to read this article. Theauthors introduce their concept by stating, “GPS cards will soonbe included in cars manufactured in the US and Europe and possibly inevery other form of mobile computer as well.” From this premise,and given that each such device can keep track of its position, theyembark on a description of how messages could be addressed to smallgeographical areas and what types of services might use the techniques.As computer scientists, they succeed in the first case and fall somewhatshort in the second. They discuss the relevant emerging protocols androuter technology to allow a sender to define a geographic area andtarget messages to the selected area. They also suggest ways for thetargets to decline to receive messages.

So far, so good. When they turn to possible services, they mentionemergency messages and geographic-multicast advertising messages. Thecase for emergency services is more believable. With sufficientencryption, the technique could also be used by fire, law enforcement,or military personnel to organize their tasks. GPS is certainlycoming.