GPS Could Speed Tsunami Warnings? Right Train of Thought, Wrong Tool.

Sure, the idea of tracking seismic activity by motion differentials is a good idea. But there's no kind way of saying that using GPS is not the best solution, and has been known to be the least best solution for quite some time. But Wired Magazine's article, 'GPS Could Speed Tsunami Warnings' certainly captured a lot of attention with a Slashdot reference, but it's definitely not the right answer because of quite a few things. Before I get into those things, I'll give you the right answer - the Inertial Navigation Unit - or Inertial guidance system. I'll explain that after I debase this thought about GPS as an early warning system.

Why GPS isn't worthwhile for Tsunami Warnings

• Line of Sight to Satellite: To get accuracy within 10 feet, a standard GPS system requires satellite lock of 12 satellites. Cloud cover, foliage, and all sorts of things can conspire against GPS accuracy - and in this context, may lead to false warnings.
• Assorted GPS Errors: There are many sources of GPS errors, which include synchronization of clocks, the ionosphere, reception of signals which are not only GPS, and also selective availability - which is supposed to be turned off in 2006, according to U.S. government release in 2000.
• While differential GPS can reduce errors, it also has the capacity to compound them, mainly related to actual system reliability.
• GPS can be jammed, even accidentally, for about $20 US at your local electronics store.

But Why Inertial Guidance Systems?

When people track satellites, they track them from points on the earth. Observatories. And for high accuracy, adaptations of Inertial guidance systems are used because they can track extremely small changes in position - including depth - and with accelerometers, can even gauge the rate of change - commonly known as acceleration and deceleration in any one or all of the axes (plural of axis). This means that when the building moves, astronomers don't get lost in the universe, thinking that a galaxies moved a few light years because the building moved a millimeter.

They are used underground by oil companies to guide drills where GPS will not work. Now... if you want to track seismic activity, wouldn't you expect the sensors to be underground - out of direct view of satellites? Of course you would. And what about earthquakes? And these inertial navigation units (INUs) are built to handle loads of physical stress - considering that they use inertial navigation systems in missiles, fighters and even commercial airliners, submarines as well as on oil drills... and that Chinese fighter jets use Fuzzy Logic within them to associate the systems to specific geography...

No, GPS is not the right answer. It's a thought in the right direction, but the real answer is the Inertial Navigaation system. My experience in this comes from working at Honeywell, Inc. in the Test Equipment department - writing and maintaining software that tested these INUs.

GPS? Stick a few INUs around the world in key points, network them using Ultra low frequency alarms, and you have something. GPS just can't handle it.

Now how does someone tell these people they are barking up the wrong tree? :-)