Navigation is easier than ever. In the heyday of ancient Greek civilization, Ptolemy put longitude and latitude on his maps, but when they were sailing out of sight of land, they had trouble using them. People could find their latitude by observations of the sun at noon, but longitude was a different matter. It was possible to make longitudinal measurements using stars at night, but you needed to know what time it was, and clocks on boats didn't run dependably. (The boat's rocking made the machinery operate inconsistently.) It wasn't until the 1700s that sailors could find where they were, weather permitting.

Fast forward to today. There is a fleet of satellites around the earth, constantly helping the planes, trains, and ships at sea know where they are. This information is useful to fishermen, hikers, and to genealogists. Today, let's talk about what a GPS is. In part two, we'll talk about software for use with a GPS, and then in part three we'll talk about how to use it.

What Is It?
GPS is short for Global Positioning System, a U.S. Department of Defense (DOD) system of twenty-four satellites, sometimes called "GPS Satellites," for providing precise location. The DOD project name is "Navigation Satellite Timing and Ranging" (NAVSTAR). GPS satellites transmit signals that can be monitored by GPS receivers. The signals contain location and time info. Most people already have modern timepieces that they wear on small bands on their wrists, and don't use the satellites for telling time. The receivers can be fixed on the Earth, in moving vehicles, or in other satellites, and are generally devices that not only receive the signals but also calculate positions with them. GPS is used in air, land, and sea navigation, mapping, surveying, and other applications where precise positioning is helpful.

When Is GPS Not GPS?
When it's GPS 3. There has been more than one GPS system. Block I were prototype satellites launched starting in 1978. Block II satellites made up the GPS system declared fully operational in 1995. Block IIF referred to the follow-on generation, but that's been scrapped in favor of planning GPS 3 instead. How would you like to be the guy with the contract to make the Block IIF satellites? Also, there is a Russian system, Glonass, the Global Navigation Satellite System (similar to glasnost but different).

Name Two Of Them
HAND HELD—$250-$1,000—these units have maps, color displays, and some can talk. Garmin, Magellan.

PCMCIA—$500-$650. They plug into a laptop slot—no battery, no wires. Teletype, Cruz.

PALM—$100-$150—I have one that is about the size of my Palm Vx, but they make them for the Handspring, too. Bring your own map. Magellan, Nexian.

"MOUSE" GPS—under $100—connects to laptop via serial port, some have a power connection too. Garmin, Magellan, Rand McNally, Delorme (duh-LOR-um)

When It Works, What Does It Do?
It can tell you where you are, to within a few meters. If you have latitude and longitude to four decimal places, you are looking at a square just about ten meters on a side. Since May 2000, typical resolution is five meters, more or less. See the links for more information about accuracy.

What's The Down Side?
You need to get a signal from at least four satellites to get a fix. Out in the open that's not so bad, but in town that can be tough. If your receiver has at least five channels you can look for one while you follow four. Some receivers have up to twelve channels, which is the maximum number of satellites that you could possibly see from one place on earth. You can't input the location into a program today. I would really like to be able to click on my genealogy program and get an instant GPS reading entered into the program. But you better take a tablet and a pencil—you can't enter it today. Many programs will let you type it, but I know of none that will read the receiver.

How Do I Know If It's Not Working?
It can be difficult getting your computer and receiver to sync up. The one that I have attaches to a serial port, and gets power from the keyboard jack. My laptop has no serial port. To physically connect the GPS receiver to the laptop, I had to buy a "port expander" that attaches to a USB port. The port expander has to be plugged into an electrical outlet to work, so I had to buy a gizmo that plugs into a cigarette lighter. I plugged a power strip into that because one outlet is never enough. With this Rube Goldberg setup in the passenger seat, I no longer have to worry about people asking for rides in my car. When I start a trip, I spend between twenty and thirty minutes in the car, doing the GPS dance, which functionally resembles a rain dance, and involves several reboots and configuration changes, killing the palm pilot hot sync manager, and the like. If I have properly placated the GPS gods, I get a signal and it's easy after that. If I haven't, I continue to make offerings until the only thing I have left to give is up.

What If I Change Computers?
Reinstall the software, reconnect the receiver.

What's The Genealogy Tie-in?
Genealogists have many uses for place. Locating and recording the location of graves, ancestral home sites, and repositories are three great examples. A less obvious tie-in is that you can spend a lot more time at the library if you don't get lost trying to find the city, hotel, library, or service station.

Link Me Up (more stars is better)

Joe Mehaffey and Jack Yeazel's GPS Information Web Site**** (Joe Mehaffey and Jack Yeazel, same, 1997-2001, 19 August, 2001) http://joe.mehaffey.com/ Many GPS product reviews, with info for beginners. GPS

Accuracy - Lies, Damned Lies, and Statistics *** (Advanstar Communications, Frank van Diggelen, 1998, 14 August 2001) www.gpsworld.com/columns/9805innov.html More than you ever wanted to know about GPS accuracy. There is math and a bibliography!

Post SA GPS Accuracy Measurements *** (Wolfgang Rupprecht, Wolfgang Rupprecht, 20 May 2000, 14 August 2001) www.wsrcc.com/wolfgang/gps/accuracy.html Easy to understand explanation of GPS accuracy.

Civil GPS Accuracy Boosted ** (Federal Computer Week, Paula Shaki Trimble, 2 May 2000, 14 August 2001) www.fcw.com/fcw/articles/2000/0501/web-gps-05-02-00.asp A bit of background on the increased accuracy of civilian GPS.

Where Do I Get A GPS Receiver? *** (Sunninghill Systems, Robin Lovelock, 2 August 2001, 19 August 2001) www.gpss.co.uk/wheregps.htm A UK site with good product information.

Topzone.com **** Maps a la carte, inc. same. 2000. 19 August 2001. www.topozone.com Enter your GPS coordinates, get a topographic map. Bruce Lee's grave? 47.6333, -122.3158. Check it out.

What Else?
The plans for the current GPS system called for replacement of all the satellites by 2006. It appears that the birds are lasting two years longer than expected, and the plans have changed. GPS 3 will have more civil services than "Block II Follow-on" had planned. It's still in the design stage.

Some Kodak digital cameras can be connected to GPS units, and put the info, along with the image, right into your computer! Now some GPS receivers come in Flash format, and can plug into those slots on cameras and handheld computers.

Amazon.com electronics has links for new and used items, with lots of pricing and pictures. They'll sell you a book about GPS use, too. It might be the easiest place to compare receiver models.