Her teacher (a former geologist) had the kids break up into groups of four each, and then he sent them out with a global positioning system (GPS) tracker to attempt to locate a special treat on the school grounds. Not surprisingly, they picked up this new technology quickly, and if he hadn't cut them off at the end of class, they would probably have ended up mapping the entire schoolyard.
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GPS and URLs
The GPS coordinate system is analogous on a number of levels to the universal coordinate system embodied in the URL. With it, you can specify longitude, latitude, and height coordinates to within a meter (not counting any obfuscation performed by military satellites to fuzz things a bit) of any position on earth. With a properly synchronised timepiece, you also have a way of providing travel time and distance between coordinates, or of creating a historical trajectory.
Graphical reference map applications
In a perfect world, the shortest distance between two points is a straight line. But in a mall, for example, the shortest distance between two points is usually past the Starbucks, up the elevator, through the food court, and by the theater. While the number of all possible routes is infinite, if you assume that a route's locus is defined as the centerline of the walkway, it's possible to create a handful of such routes (a three-dimensional network) that can be used to describe the mall.
A decent mall map application would likely include some association between the symbolic and the visual map. Using a language such as the XML-based scalable vector graphics (SVG), it may be possible to create a graphical reference map with the position of map elements (doors, walls, escalators, entrances) rendered to the GPS coordinate system. Such an application would also group related elements (such as the general outlines of a store, perhaps to a level including permanent shelves and counters) so that each such group could be identified as a store, a restroom, a security station, and so forth. Consequently, a mall map application could create a live “You are here” display.
A language is born
One means to encode routes has been proposed by Charon, Inc., the GPSml markup language, to be submitted as a note to the W3C later this year. In this XML-based system, a GPSml document consists of one or more collections of three principal types: a waypoint, a route (a named collection of waypoints), or a track (which combines locations with a time coordinate). A waypoint consists of a position, an identifier that defines a waypoint relative to the document, and a display attribute that is intended to provide some indicator of how the waypoint should be visually identified.
In some respects, it's the identifier that is most critical for Web deployment. An identifier can be any label, and doesn't have to be unique beyond the scope of the document. However, it can be. One way of understanding the importance of this identifier is to associate it with a Uniform Resource Identifier (URI). With such a URI, you could effectively assign to that location an application that will run when the location is referenced in some manner (you get within five feet of that node, for instance). This application could be a Web service, retrieving contextual information about the location; it could notify the tracking application to recheck the route that you're on to make sure it is still the most efficient one; it could bring up a list of sales in all of the adjacent stores. It could even retrieve a message that's read out loud by a vox program: “Go up the escalator past the Radio Shack store, until you come to the fountain, then turn right.”
Technological consequences
One of the more interesting, and potentially troubling, aspects of a GPS device is that it has a unique identifier, which can be associated with its owner. This identifier can be used as part of a person's XML profile. Marketers live for this kind of information; even without knowing anything about you, a marketer could read the identifier being transmitted to Web services giving GPS information for the device and develop a profile showing that the last three times you came to this mall, you bought clothes from Nordstrom's and a network card from Radio Shack. This kind of demographic information could be used both in general a manner, to see which stores need to be better promoted, and in an individual manner, to offer a discount on network cables for that card you bought last time.
A given point in space may have different meanings to different people, of course. Typically, any application that uses GPS positioning would define its own GPSml document that would be provided as part of a Web service, creating the relevant context. That's why a GPS location by itself is insufficient to be used as a URL—there may be many contexts associated with the location, and it is only by accessing the appropriate service that a given context can be applied.
Geeplogs are next
The Really Simple Schema (RSS) specification is currently gaining ascendancy in the world of blogs and news feeds, but in the future it, or something very much like it, will emerge as a way to publish public GPS contexts that can be queried about a given area. Of course, the least interesting will be the ones published by the owners or promoters of the site. More likely (and lively) will be the GPS equivalents to blogs, in which a person could narrate a specific tour with his or her relevant commentary, possibly with photographs, video feeds, and links to subjects that may or may not be approved by management. There could be several such geeplogs (GP logs) in any given space, providing a virtual metaphorical context to the area—digital graffiti.
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Interesting concepts presented in this article, but some of the basic facts are not correct.
While GPS coordinates can be regarded as absolute, they are not - any position is still relative to the arbitrary spherical geometry adopted by the designers of the system. Beauty of the system is that it is earth-centered, not based on any sort of map projection, and therefore universally applicable.
GPS receivers are not all the same - like with most consumer goods, you get what you pay for. The cheaper (handheld) variety might give you 5-10 metre precision, and if you want real precision, better than a centimetre, you will have to pay $10,000 plus. And don't believe the readouts - just because it displays coordinates to 0.1 of a metre doesn't mean the result is that precise.
Unfortunate choice of an example - a GPS receiver will not work inside a mall, it needs unrestricted access to the sky, even trees are often a problem. A better choice of example would use road networks, as many large cities have already been extensively mapped with GPS coordinates. Similar principles as described in the article would still apply.
Specialised mapping and surveying expertise is still required to setup these systems - the unintiated who think it looks simple usually end up with an inadequate, inaccurate and unusable mess. Worse still they often don't realise it!