Global Positioning Satellite Units and the HP Palmtop

© Beverly Howard, Austin, Tx, 2002
Content may be "linked" with permission but not reposted
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This article first appeared in March/April 2000 edition of The Palmtop Paper

It has and will be edited to correct minor errors, offer new and improved suggestions and to keep hyperlinks current.

Additional Links to more GPS Info;
GPS General
Delorme's TripMate
Magellan's Meridian
Raw Map Reduction
GPS Turn by Turn Routing using Google Maps

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 were no options to get distances to and from any point on the ground unless the ground was visible and you could find ladmarks on a visual map.

Without having sight of the land, the best way to figure this out was to know exactly which direction you were headed and precisely how fast you were traveling and from those pieces of information, along with your starting point and the time you were in the air, you could calculate where you were... approximately. Getting direction information from two or more radio aids could then be used to confirm one's approximate position.

Then, it was not uncommon for my father and I to climb above a solid layer of clouds in the '53 V-Tailed Bonanza and cruise for five hours or more with no land in sight. When we descended through the clouds we felt pretty good if we were within five to ten miles of our calculated position....

Well, 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 has given me a real appreciation of these new tools. In short, they blow me away and 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.

The Different Flavor and Capabilities 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 tell 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. These have all the electronics, the antenna and the display all in one unit. They're small and the display, though readable, is small.

2. Mounted units that 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. These units 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.  The unit that I will be referencing in this article is the Delorme Tripmate unit that was shipped with earlier versions fo Street Atlas.

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

The hand held units have the advantage of being very portable and, in most cases, they are weather proof. On the other hand such units sacrifice flexibility and display capabilities.  In addition the hand held units with displays cost significantly more than GPS displayless reveiver units with only a serial port.

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 terminology, i.e.,the jargon, of GPS navigation.

There are several fundamental tasks that a GPS unit can do for you. Give you position and altitude information, indicate your current direction of travel and how fast you are moving, show you the distance and direction to previously stored places, display a map that includes a marker on the map that indicates where you are at the moment and finally, keeping a record of where you have been.

Where Am I and Where Am I Headed?

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.  What may be of more use is to know which direction they are traveling and how fast they are moving.

How Do I Get From Here to Where I Was Earlier?

The next concept is the "waypoint" approach which really came into it's own 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 visually 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 out, 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.

What is Near Here That I Can't See Yet and How Do I Get From Here to There?

The next step up the ladder involves learning about "moving map displays"  This is where the hand held units and the computer units begin to part ways.  It's also where the prices of the hand held 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 also display your current direction and speed as well.  In addition, if you have a way point selected, the indicator will also show the difference between your current direction and the direct path toward the way point.  In general, maps are simply tools to expand your vision beyond your line of sight and give you the information necessary to get from where you are to someplace that is not yet visible.

Here is where the computers come into their own.  Because of the larger displays and storage options of modern laptops, much more navigational 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 when you encounter the event. 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 not only 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 back-track to the missed intersection I looked at the computer display and found the shortest and most efficient route to get back on course.

It's hard to describe how much the GPS unit added to traveling.  In the South Carolina costal region it has allowed me to explore new routes between familiar places that I never knew existed.  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 for the LXGPS Software

I missed the first announcement of the LXGPS software program and I regret not having found this package sooner. I had been busy using two other GPS programs on both the Palmtop and on a laptop while traveling cross country.

When I downloaded LXGPS, version 1.5, from the S.U.P.E.R. site and installed it on my Palmtop I was impressed. The program in very intuitive and handles the Tripmate GPS unit transparently and flawlessly. For instance, I could turn off the Palmtop, disconnect the serial cable, come back an hour later, reconnect the cable, turn the power on, press "Monitor" and the program would reinitialize the Tripmate and get a reading in under a minute. The other two programs failed to do this.  The author also has some additional navigation related programs on his personal site at

Furthermore, the LXGPS program has a variety of customization options that none of the other Palmtop GPS programs offer. For example, in addition to on-map displays of waypoints, a course line to pre-picked way points shows on screen. Even the map scroll is controllable. You can enter a number that represents a percent of the screen's area. When the position marker reaches this percentage of the screen, the map will shift and the position marker will be in the center of the screen again.

Finally, the cost! The author calls LXGPS copyrighted freeware but also indicates that it's "e-mail ware."  You'll want to send him e-mail about your impressions and findings as your payment for the software. If you've got a Palmtop and access to a NMEA 0183 serial port GPS such as the Delorme Tripmate, don't let this combo go by.

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 back 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 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 that the Street Atlas program can't do. (For a detailed description of the process of converting map images, click here)

Even though the Palmtop's display is better than those in most hand held 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 back lit 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 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 top pocket of a back pack and the Palmtop in a coat or shirt pocket and with the LXGPS software the package would blow most of the handheld units away.

Where Was That Truck Today?

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 where a delivery person was at any given time.

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.

With the logging options of LXGPS, it would be possible to build a recording tracker for a gravel truck company for under $500 that would generate time and position proofs when windshield damage claims were presented.

Things GPS Can't Accomplish

The TV commercial that shows a fellow walking around his house, with a GPS unit giving him his position as he walks, is a fantasy. GPS units, or at least their antennas, 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, we 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.

The concept of GPS accurately tracking your walk around the house is not, however, 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 as we walked from one side of the small parking area to the other.  All you need is a home without a roof.

Many of GPS users report that they are satisfied by simply placing the GPS receiver on the dash of the car, but, whenever possible, it is very important to try and place the receiver or antenna on the roof or anywhere to increase it's view of the sky.  In most cases, simply moving the receiving antenna 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.  GPS units need to be told their approximate position before they start and, when they have this information, they can generally begin giving position information in several minutes.

Finally, always remember that 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...
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