GPS


I’ll make this quick.

I’m deep into preparing a briefing/presentation/class on the issue of magnetic declination and the easiest rules to follow when you need to apply it.

What’s magnetic declination, you ask?  Sorry, that’s not the topic of today’s post.  If you really – REALLY – need more information right now check out the Wikipedia page on Magnetic Declination.  I’ll be referring to it in a later post.

Anyway…  I was mentioning to a friend that I was working on this presentation and he commented “Does anyone really care about that anymore?  I think everyone has just gone out and bought a GPS.”

I actually get that reaction a lot when I talk to people about compasses and using a map and compass to navigate.  “Compasses confuse me.  I’d rather just use a GPS” seems to be the common refrain.

(For the uninitiated, GPS stands for Global Positioning System, or space-based satellite navigation system.  There are several operational (US, Russian) and developing (the European Union’s Galileo) satellite navigation systems, but ‘GPS’ has become an almost a generic term used to describe the US developed and operated NAVSTAR system.)

I live and work in the world of GPS.  I’m a geospatial professional and I run the GPS-based survey and data collection program at the World’s Busiest Airport.  Every day I am thinking about, using, training, developing policies on and attending meetings about GPS and how we use it at our airport.  Everything from upgrading our high-precision GPS receivers to providing airport-specific input for the FAAs GPS-based NextGen precision approach program to review and quality control of project layouts generated using GPS-based survey systems.  And more.

I am the biggest cheerleader for the GPS system and GPS-based technologies.  GPS is perhaps the best example of a project that only the United States could do, and do right.  The driver who switches on his Garmin Nuvi for the drive to the airport is leveraging tens of billions of dollars and decades of research, development, testing, deployment, maintenance and upgrades.  All paid for by the US taxpayer, and all free to any user anywhere in the world.

Conceptually the GPS system is simple – satellites in space broadcast their position and your receiver (example – our driver’s Garmin Nuvi) uses time shift calculations to determine the precise distance from your location back to the satellite.  Once the receiver picks up and processes signals from at least two more satellites it can triangulate your position.  The size of the position ‘triangle’ determines the accuracy of the position fix provided by the receiver, but in general a modern receiver tracking three or more good satellite signals can locate you to within about 15 feet of your true position anywhere on earth.  That’s pretty damned good by anybody’s reckoning.

GPS has revolutionized many industries and spawned completely new ones.  GPS systems are so pervasive that most people no longer give them a second thought.  Today GPS technology tracks your package as it travels from the retailer to your door, and it tracks the paroled felon sporting the nifty ankle bracelet.  GPS technology manages the hand-off of your phone conversation from one cell tower to another as you speed down the interstate, and GPS technology guides the angle of the bulldozer blade working a local road construction project.  Anything that locates you on a map is universally identified as ‘GPS’, even if the function has nothing to do with satellite-based navigation.  GPS has become an integral part of our lives and impacts us for the better every day.

And yet, GPS is a system with serious limitations.  It can’t locate you indoors, in tunnels, under overpasses, in dense forests or even in the man made canyons of large cities.  The signals can be easily corrupted, blocked or bounced around so much they are virtually useless.  The entire GPS system is a delicate balance of high technology and rocket science, enormously expensive to maintain and upgrade.  At some point the GPS system – certainly a system that succeeds what we have now – will fail.  It will fail due to funding shortfalls, political upheaval, changing national priorities or simple neglect.  This failure is merely a recognition of a historical inevitability – man made systems always fail at some point.

Long after the GPS satellites go cold and dark in their far orbits and GPS receivers become little more than technological oddities, the magnetic compass will continue to offer reliable wayfinding.  Using a compass (along with a map) is not easy or intuitive for most people, but once learned it provides a reasonably accurate, reliable, steady and ‘always on’ navigation capability that can not be turned off by man’s whim or neglect.  I feel fairly certain that at some time in mankind’s future we’ll be back to navigating using the simple, reliable magnetic compass.  It’s inevitable.

That’s why I still practice my map and compass skills.

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