by Phil Romig Jr
If you received a new GPS receiver for Christmas, it may have gone something like this:
You were thrilled to discover that it was small and light enough to fit in your pocket and that it had a big screen that could display a million colors. It could determine your location, find your car, take pictures of your daughter’s wedding, play video games and file your income taxes—and you couldn’t wait to use it.
After Christmas dinner, you figured out how to install batteries and turn it on. The screen lit up, and a message or bars at the bottom indicated that it was acquiring satellite signals. While it was searching, other stuff appeared on the screen—possibly icons representing different things it could do. Some were self-explanatory, and you were able to read your coordinates and see your location on a map. But other functions weren’t obvious, and you didn’t have any data even if you knew how to use them. After a while, you got frustrated and put the GPS in a safe place until you had time to figure it out.
(Notice that I haven’t mentioned anything about you reading the instruction manual. No one does that any more, and they probably shouldn’t. Manuals tend to be boring—you don’t know what the arcane words mean and they contain too much information to remember. Better to just start doing things, then use the manual when you need help. Better yet, download the manual so that you can search for key words or ask questions in an online search engine. But I digress.)
After you left your new GPS alone, it surreptitiously slipped under a stack of papers on your desk or climbed into your box of hiking gear. When you were ready to learn more, it was lost. It had IPOIO (the “Innate Perversity of Inanimate Objects”)—probably an infection caught from your cell phone.
When you finally found it, IPOIO had spread to the functions. Icons or labels would appear to say one thing but then seem to do something else, and you couldn’t find answers to your questions in the manual. You probably did what my fishing buddy Lennie did with the GPS I gave him a few years ago. He put it away in disgust and began wondering whether he could trade it for a basic necessity like another fly rod.
I understood Lennie’s frustration. My wife’s computer has a bad case of IPOIO: it does something malicious every time she uses it and then tries to shift the blame to her. But it is not necessary to have a priest exorcise IPOIO. The right approach can help you not only learn to use your GPS, but can give you a good feel for what it can and can’t do and how much to trust it.
You learn to play baseball by hitting, throwing and catching a ball, not by reading a manual. As you learned, people told you the rules and taught you how to throw a curve. You learned by doing and having fun. You can do the same thing with your GPS in four easy steps:
- Start with determining location. Be sure you know how to turn on the GPS and save a location, then to do the following:
1. Pick places nearby that can be identified on a map or satellite photo—street corners, bridge abutments, the street in front of your house, etc.
2. As you walk around town, carry your GPS with you and, at each place, have it record and save a “waypoint.”
3. Save the same waypoints at different times on different days.
4. Get the coordinates for the same points from topographic maps, Google Earth and other sources.
5. After a couple of weeks, compare all of the coordinates for each waypoint. How much do GPS coordinates vary? How much do they differ from the other sources?
This will give you a good feel for how much you can trust GPS locations, and if you do it long enough, you will begin to understand how weather, vegetation and terrain affect accuracy.
- As you experiment with locations, you will find problems. The GPS coordinate system may not be the same as the topographic map. There may be a large difference between the map location and your GPS location. Like baseball, you need to learn the “rules:” why you get different locations with different datums, how UTM is different from Lat/Lon, etc. Then you can set up your GPS so it operates according to those rules. The BCL website has a page that explains the rules, but you may need the user manual to learn how to set up your GPS.
- After you are comfortable with location, you should start using “tracks” to determine where you have been (how far, what direction, how fast, etc.). As you did when learning about location, carry your GPS and save the track information as you move around town. If you repeat some routes several times over a few weeks, you will become familiar with the use of the GPS and develop an understanding of its accuracy, capabilities and limitations.
- The last step will be planning, downloading and following routes. Again, an easy way to learn is to create and follow routes for trips that you make frequently (for example, I walk a mile each way to work). This is the step where you will also need to learn how to upload and download data to and from a computer. After following a few familiar routes around home a few times, you will have much more confidence in your ability to follow one in the backcountry.