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Global Positioning Satellite Units and the HP Palmtop

A pilot comes down to earth and finds that GPS is just as great for getting around on wheels.

By Beverly Howard

 I grew up in an aviation family and can even remember my first flight as a toddler in the mid- 1940's, visually recalling that the plane was a twin-engined World War II Cessna, nicknamed "The Bamboo Bomber." Even before I started elementary school, I was serving as a navigator on cross country flights with my father.

 In those early years, radio navigation aids gave directional information only. There was no way to get distances to and from any point. The best way to figure this out was to know exactly in which direction you were headed and exactly how fast you were traveling. From that information, along with your starting point and elapsed time in the air, you could figure out where you were, approximately. Getting direction information from two or more radio aids could then be used to confirm one's approximate position.

 It was not uncommon for my father and me to climb above a solid layer of clouds and cruise for five hours or more. When we descended through the clouds we felt pretty good if we were within several miles of our calculated position.
 
 

Things Have Changed
Most recently the widespread availability of Global Positioning System (GPS) units has changed the way I navigate both in the air and on the ground.

My early experiences in navigating have given me a real appreciation of these new tools. In short, they blow me away. I am having a blast playing and traveling with GPS technology. What also amazes me is the price for something as useful as a GPS unit. Today, the average person can walk into a sporting goods store, hand over $200 and walk out with a palm-sized device that will locate itself anywhere on the planet, give or take 50 feet.

A Variety of GPS Units
Basically, GPS units "know" where they are on the earth by collecting signals from a constantly changing "cloud" of satellites that circle the earth in polar orbits. How they show you what they know determines the nature of a particular unit. There are currently three different types of GPS units.

 1. Self-contained GPS units have all the electronics, the antenna and the display in one unit. They're small and the display, though readable, is small.

2. Mounted units consist of a master display unit inside a vehicle and an external antenna. Such a system might be installed on a boat, car or truck.

3. Units with no display capabilities pass along what they know to a computer that has special software installed. The software displays the information on a large screen, usually in the form of a point on a map.

 Many, but not all, of the commonly available handheld units have serial ports that will let you hook them up to a computer.

 The handheld units have the advantage of being very portable and, in most cases, they are weatherproof. On the other hand such units sacrifice flexibility and display capabilities. In addition the handheld units with displays cost significantly more than units with only a serial port. One manufacturer deliberately disables lower priced units so they won't work properly if you move faster than 90 mph. This is supposed to motivate you to purchase an "aviation capable" unit.

 People have apparently been buying these devices not knowing how to use them. I would bet that most of the personal GPS units spend all but the first few days in a closet or drawer. They are great little units but most people have problems with the concepts of how to use them effectively. You do need to have access to maps and you need to know how to read a map. It also helps if you know some of the jargon of GPS navigation.

 In this article, I will try to explain some of the terminology of GPS technology and describe the pros and cons of using a GPS unit with the Palmtop.

Latitude, Longitude and Waypoints
The first and most basic information that a GPS unit provides is position information in the form of latitude and longitude coordinates. For many people this is a totally useless piece of information unless they have a map with latitude and longitude markings and know how to read a map using this information.

The next concept is "waypoints" which really came into being with the advent of GPS. To best understand this concept, visualize a fisherman with a GPS unit who launches his boat in unfamiliar waters in the early morning. He begins by capturing the location of the launch ramp as the first waypoint. Then he proceeds to find a great early morning fishing spot. When that plays out, he moves on and finds a second good spot, and then another and so on. At each good spot, the fisherman takes a moment to record a "waypoint."

At the end of a long day, with darkness falling, the fisherman is able to use his GPS unit to find his way back to the launch ramp. When the previously recorded way point is selected, the GPS unit then displays both the direction and distance from the unit directly to the selected way point, allowing the fisherman to return even if he was totally lost.

 When the fisherman returns next week he can use the waypoints to return to the exact spots he marked to fish again even if there is no land in sight. This same concept allows hikers to enter a trackless wilderness and record a series of way points on the way in, then select "reverse course" and the GPS will post distance and direction for the hiker to reverse his course. At this point you can probably see the potential consequences if either the hiker or the fisherman had put total dependance on the GPS unit and the batteries went dead.
 
 

Moving Maps
The next step up the ladder involves learning about "moving map displays" This is where the handheld and computer units begin to part ways. It's also where the prices of the handheld units begin to climb as well. Some GPS units will show only numbers. Others will display a map as well. A cursor or crosshair appears on the map showing the position of the GPS unit on the earth. As you move around the indicator moves on the map to update your position. Most GPS units and software display your current direction and speed as well. In addition, if you have a waypoint selected, the indicator will also show the difference between your current direction and the direct path toward the waypoint.

 Because of the larger displays and storage options of modern laptops, much more GPS information can be displayed. Computers also let you have more options in how the information is displayed, processed and saved. Sure, a Pentium machine with a fancy display would be great but the HP Palmtop provides a platform that can significantly outperform many self-contained GPS units.

 I currently use two computer- based platforms depending on the situation and resources. The most powerful platform consists of a laptop, Delorme's Street Atlas software and Delorme's Tripmate GPS receiver. On the laptop, with the GPS unit attached and running, the display reveals a full color street map with the tip of a moving, green pointer showing your exact position and direction. The software interface can be zoomed in or out with a single keystroke. You can start from a display that shows the entire United States and zoom in so that the display focuses on three or four city blocks.

 The preferred mode of display is "Automatic Panning" that moves the map display as the pointer nears any edge. Delorme Street Atlas adds another dimension when you use its route generation capabilities. When GPS tracking is initialized, with a route in place on the map, position information activates voice commands that alert you to upcoming exits or intersections with verbal instructions on how to proceed Initially, I thought the computer would be more of a distraction than an aid but after several short trips around town and a long trip out of town, I found that the distractions were significantly less than using a paper map.

 First, the constantly updated display removed any surprises. I could glance at the display when convenient and know where I was on the map without searching. I found that as I approached cities or intersections where distractions would be a factor, I already had all of the information I needed before I arrived. Doubts about how to proceed were significantly reduced.

 This didn't mean that I didn't get lost. The first long trip was on a route that I had driven years earlier. I was very pleased with how things had gone until I was leaving a small town. I remarked to my wife that the unit had been operating flawlessly all day but now it was showing us at the wrong place on the map. It took a few seconds for me to realize that the GPS unit and the computer were correct and I had missed a turn.

 It immediately became clear how easy it was to spot such mistakes. But in this case we were several miles off course by the time I realized my mistake. Rather than backtrack to the missed intersection, I looked at the computer display and found the shortest and most efficient route to get back on course.

 In the South Carolina coastal region the GPS unit has allowed me to explore new routes between familiar places. I don't think I will ever make another extended road trip without it.

 For true portability, I can't beat using the HP 200LX along with the excellent LXGPS program and the TripMate GPS receiver. However there are some drawbacks. First, if you want a "moving map display" you'll have to generate all the maps and transfer them to the Palmtop. If you don't want to deal with maps, the LXGPS program will display your position, speed and direction as well as let you use way points. (See the sidebar for a review of LXGPS.)
 
 

Generating Maps: Frustrating but Worth It
I use maps with LXGPS that I generate from the Delorme Street Atlas. Admittedly, it takes a bit of time and practice to convert the yellow background and red streets to a 1-bit black and white PCX graphic. However, when I manage to get the black and white pictures right, they really look good on the Palmtop.

 The next step in the process involves calibrating the maps for use with the LXGPS program. I start LXGPS and match two points on opposite corners of the map to their exact Latitude/Longitude coordinates. After this calibration step, the tracking on the maps is amazingly accurate. I can even tell on which side of a highway I am traveling using a 1280x1024 pixel map covering about 30 miles across.

 In addition to automatic panning to track your position on maps that exceed the size of the Palmtop's display, you can configure LXGPS to set the point at which the panning occurs. This is something the Street Atlas program can't do.

 Even though the Palmtop's display is better than those in most handheld GPS units, it has been my experience that the Palmtop's screen is too small to be used effectively while driving. It's also much less visible than any backlit display. In a car or boat, with sunlight hitting the display and warming it up, the contrast keeps changing and this makes the unit less useful.

However, if you are a minimalist, the only two necessary components are the Palmtop and the TripMate GPS unit. Both can run on their own batteries. It's feasible for a hiker to use both devices by placing the receiver in a backpack and the Palmtop in a coat or shirt pocket.
 
 

Logging Is an Added Bonus
The final mode of operation is "logging" which can be done while using other features such as the moving maps. When logging is started the Palmtop will open a disk file and repeatedly store time and position information in the file. If you want to know where junior goes when he borrows the car, put the Tripmate antenna on the roof and the Palmtop in the trunk. You'll know exactly where he's been. I say this facetiously but, on the other hand, a delivery service could use something like a TripMate/Palmtop package that would cost around $400. It could be used to analyze delivery routes as well as keep track of a delivery person's position.

In reality, the concept and components have become so common that they are already showing up as options when you rent a car or buy a new car with the NorthStar system already built in. It's totally conceivable that, in the next couple of years, such units will be installed in pizza delivery signs clamped to the window of a student's car. They could be used to transmit verbal directions about how to get to the next delivery through the car's FM radio.
 
 

The Downside to GPS
The TV commercial that shows a guy walking around his house, with a GPS unit giving him his position, is a joke. GPS units must have a totally unobstructed view of the sky to function. Tree leaves, roofs, and other overhead obstructions will effectively block GPS signals. While you might get enough information to use a GPS unit to navigate downtown in a big city, you'll get the best results on an interstate somewhere in Texas. On a recent trip to South Carolina, I decided to travel the back roads. It was a beautiful drive with trees serving as a canopy overhead. The problem was that the GPS unit showed gaps in its tracking and logging. Tracking your walk around the outside of a house is not unreasonable... at one computer club meeting, I was able to demo the TripMate by walking around the library parking lot and have the pointer accurately track our position.

 A lot of GPS users report that they are satisfied by simply placing the GPS receiver on the dash of the car, but, whenever possible, try and place the receiver or antenna on the roof or anywhere to increase it's view of the sky. In most cases, moving from the dash to the roof will double the number of satellites resulting in a corresponding increase in accuracy and reliability.

 GPS also takes time to start up. When you take a new GPS unit out of the box and turn it on, it may take more than an hour to determine its current position. After GPS units are told their approximate position, they can generally begin giving position information in several minutes.

 Finally, if you're using your GPS to navigate your way up the Mississippi river and the GPS's batteries go dead or the unit fails or the government decides to turn the system off because of a national crisis you'll be up a big creek...

LXGPS: A Review

iPhone Life magazine


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