Just as one would expect with a leading-edge technology like GPS, there are some extensive resources available on the World Wide Web for checking on the status of GPS and learning more about how the system works. For the computer-equipped navigator with a curiosity about GPS, a whole range of Web sites have sprung up to indulge one’s interest. To uncover a comparable amount of information, non-computerized mariners would have to buy a few books and spend some time on the phone.
The World Wide Web is, of course, only one facet of the Internetthat network of 120,000 networks that is estimated to have more than 20 million users. To access the Web, you need a computer (nothing less than a 386 makes sense), a modem (go for the maximum speed 28.8 kbps units for Web surfing), an internet service provider for getting hooked directly into the net, and some software called a Web browser that allows you to access Web sites. Getting to a Web site requires an address called a Uniform Resource Locator (URL) The particulars of getting onto the Web are available in a variety of books and magazines, so we won’t go into detail here.
The starting place for any web-based look at GPS should be the Coast Guard’s Navigation Information Center in Alexandria, Va. (see Number 1 on URL list below). Once connected to the Navigation Center’s home page, you are faced with a series of choices of where to go next. The subjects include pages on GPS, DGPS, loran, Omega, radiobeacons, boating safety, USCG telecommunications policies, etc. The essence of the World Wide Web and its hypertext markup language (HTML) is the ability to move around and look at those items that interest you while skipping things that are not so compelling. This approach allows you to focus down on GPS and DGPS information and leave all that info on Omega and boating safety for some other visit.
By delving into the GPS page (it can be accessed from the Navigation Center home page) you can get information on the latest GPS status message, the latest GPS satellite almanac, the latest Notice Advisory to Navstar Users (NANU), GPS outage reporting, GPS general information, and additional arcane topics for the avid GPS aficionado. But that is by no means all the GPS information available on the Web. There several Web sites acting as clearing houses for GPS information. One of the best of these is Paul Tarr’s GPS reference links (No. 2 on URL list). This site has an extensive listing of GPS resources, as well as information about how GPS works, and links to related sites, like information on GLONASS, the Russian equivalent to GPS. MIT’s Lincoln Labs maintains an interesting site (No. 3) with GPS and GLONASS data. Under contract to the FAA, Lincoln Labs has done considerable work on prototype combined GPS/GLONASS receivers. For those who want to go to the source, you can even access the Coordinated Scientific Information Center of the Russian Space Forces (No. 4). Another site with a prodigious level of information and links to other GPS sites is John Beadles’s introduction to GPS applications (No. 5). An excellent place to go for an explanation of GPS and to see how GPS is applied to a particular field of endeavor (in this case it’s surveying, not navigation) is University of Texas overview of GPS (No. 6). This site describes how GPS works and how it is used in surveying and for geographical information systems (GIS).
Overall, the Web is a rich resource for those mariners interested in learning more about GPS.
