Geography Reference
In-Depth Information
Receivers
A GPS receiver usually consists of the following:
An antenna (whose position the receiver reports)
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Electronics to receive the satellite signals
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A microcomputer to process the data that computes the antenna position and to record position values
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Controls to allow the user to provide input to the receiver
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A screen to display information
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More elaborate units have computer memory to store position data points and the velocity of the
antenna. This information may be uploaded into a personal computer or workstation, and then installed
in a GIS software database. Another elaboration on the basic GPS unit is the ability to receive data from
and transmit data to other GPS receivers—a technique called “real-time differential GPS” that may be
used to considerably increase the accuracy of position finding.
Receiver Manufacturers
In addition to being an engineering marvel and of great benefit to many people concerned with spatial
issues as complex as national defense or as mundane as refinding a great fishing spot, GPS is also big
business.
Dozens of GPS receiver builders exist—from those who manufacture just the GPS “engine,” to those who
provide a complete unit for the end user. Prices range from somewhat under $100 USD to several thousands.
The U.S. Department of Defense
The U.S. DoD is charged by law with developing and maintaining NAVSTAR. It was, at first, secret.
Five years elapsed from the first satellite launch in 1978 until news of GPS came out in 1983. In the
approximately three decades since—despite the fact that parts of the system remain highly classified—
citizens have been cashing in on “The Next Utility.”
There is little question that the design of GPS would have been different had it been a civilian system
from the ground up—but then, GPS might not have been developed at all. Many issues must be resolved
in the coming years. A Presidential Directive issued in March of 1996 designated the U.S. Department of
Transportation as the lead civilian agency to work with DoD so that nonmilitary uses can bloom. DoD is
learning to play nicely with the civilian world. The use of GPS for automobile navigation, location-based
services, cell phone location, fleet management, emergency services, and so on has been little short of
astounding. And many devices with GPS devices report their positions. The great advantage of GPS in
daily use is you know where you are. The scary part is “they” know where you are (and where you have
been) as well. George Orwell's 1949 novel
Nineteen Eighty-Four
begins with:
“There was of course no way of knowing whether you were being watched at any given time. How
often, or on what system, the Thought Police plugged in on any individual wire was guesswork. It was
even conceivable that they watched everybody all the time. But at any rate they could plug in your wire
whenever they wanted to. You had to live—did live, from habit that became instinct—in the assumption
that every sound you made was overheard, and, except in darkness, every movement scrutinized”
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