Tikalon Blog by Dev Gualtieri

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Quo Vadis?

May 30, 2012

The title of this article, "Quo vadis?," is Latin for "Where are you going?" Aside from the philosophical implications of this simple phrase, there's the practical matter that every day we take multiple journeys to places such as work, school, and food markets. Our local routes are imprinted on our memories to the extent that we often drive on "autopilot ," not really thinking about the process that brings us from point "A" to point "B."

When I was younger, gasoline was much less expensive, and there was considerable competition among vendors. Most intelligent people realized that there was no real difference between one brand of gasoline and another, so the service stations would give you free items, generally when you filled your fuel tank . There would be beverage glasses , plastic toys , and volumes of children's encyclopedias . There were also road maps .

Shell Oil road maps, circa 1970.

It's amazing what you find in the glove compartment of the family car.

These Shell Oil Company maps date from the late 1960s.

(Photo by author).

About a decade ago, everyone needed a map if they were traveling a distance from their home, through places they had never been before, to an unfamiliar destination. Today, we have the ubiquitous Global Positioning System (GPS), a much more important spin-off of space technology than space food sticks .[1]

The essential principle of GPS is so simple that even a high school geometer can grasp it. GPS satellites transmit radio messages that indicate their position and the time that the messages were sent. This defines a sphere whose radius is the speed of light multiplied by the transit time from the satellite to a receiver .

The spheres of two satellites will intersect in a circle , and the sphere of a third satellite will define two points on the circle. One point will be wildly inaccurate, and the other will define the position of the receiver. This procedure is called trilateration .

Since the speed of light is so large, even small timing errors will produce a large position error, so this process is usually done with one, or more, additional satellites in the mix. In a recent article (Baking Powder's Harvard Pedigree, May 1, 2012), I mentioned my opinion that taxpayer dollars allocated to the US Food and Drug Administration (FDA) was money well spent. This observation applies also to the GPS satellite system, which is operated by the US Government as a public service .

Garmin GPS

My personal GPS, a Garmin Nüvi , received as a gift from my daughter and her husband.

(Photo by author).

The present accuracy of consumer GPS receivers, such as the one shown above, is about twenty meters , but there are so-called augmentation systems , particularly FAA WASS , that bring the accuracy below a meter.

GPS was originally released for public use with 100 meter accuracy, a mode called "Selective Availability " (SA); but SA was removed on May 1, 2000. At that time, many users were using additional ground-based transmitters in a method called differential GPS to increase accuracy, so the decision was moot. This is how WASS and similar augmentation systems work. However, turning off SA was an aid for positioning on low cost receivers.

Many mobile devices, such as cellphones , now incorporate GPS, which leads to many new applications, and new privacy concerns. Such technology helps when you're looking for the nearest pizza , but it might be a problem if a stalker is looking for you. Sometimes the stalker is one of the many persistent marketers and advertisers .

An example is shown by a recent General Motors patent application , "Method Of Advertising To A Targeted Vehicle."[2-4] As its name indicates, it's a method to display billboard ads to a particular vehicle. Although GM's present OnStar system does not track vehicles, we might find a future in which such a system finds that you've been driving for several hours, surmises you need a break, and flashes a billboard ad for a restaurant targeted at you.

The restaurant is selected based on your past eating habits, as determined by the locations of other restaurants at which you've stopped; and this is a "click-through " billing for the restaurant, since it's verified that you actually did stop there. You get a meal, and someone gets paid a dollar, or two.

Although some sensitive GPS receivers will work inside buildings, they aren't very useful, except to indicate that you are inside a building. One complaint I have about the "anchor stores " in shopping malls is that they try very hard to camouflage their exits that lead to the mall, itself. They would rather you spend your money with them. That's when I could use an indoor GPS with a map of the mall.

Researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA (Stuttgart, Germany ) have collaborated with several industrial partners to produce an indoor GPS-like system. I've mentioned Fraunhofer research in a number of previous articles.[6]

This positioning system does not rely on radio signals, but on dead-reckoning , in which speed and direction are determined by an electronic compass and accelerometers . It uses a USB device that plugs into a tablet computer or other devices, such as smartphones (see photograph).[7]

Fraunhofer navigation sensor for interior spaces.

Fraunhofer navigation sensor for interior spaces.

(Copyright 2012, Fraunhofer-Gesellschaft).

To operate, a resident application program downloads a three-dimensional building plan from the Internet . This could be accomplished by reading a QR coded plaque that would also set the initial position. The Fraunhofer team demonstrated this device at the Sensor+Test trade fair in Nuremberg, Germany , May 22-24, 2012.[7]

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