If you’re like us, as much as you enjoy high tech stuff, the VCR still blinks 12:00. God forbid you actually take the time to read the instructions, who has time for that? Do yourself the favor of taking the time to read up on your equipment enough to comfortably know how to use it. Trust us, the first time your trusty GPS unit saves your are from being hopefully lost, trip ruined, and humiliated in front of your pals, you will thank God, yourself, and maybe us too? Again here are the basics.
Getting a Fix
GPS units are referred to as receivers because that is what they do, receive satellite radio signals. Unlike other types of signals, GPS works on line of site. This means the receiver’s antenna must have a clear view sky to work properly. The good news is that it will work at night, in fog, in a blizzard, or any other extreme weather conditions. Anything overhead, however can limit or block out the signals. This includes heavy vegetation, buildings, or steep cliff walls. If operating in a dense forest or jungle, a clearing may have to be found to obtain a stronger reading.
Out of the 24 orbiting satellites, 12 are in each hemisphere. Receivers need to read at least three at a time to “triangulate” the equipment’s exact location. Four are needed to provide a more actuate three-dimensional fix that will provide elevation. The receiver’s Satellite Status Page will show how many satellites are locked in at any given time.
It may show the satellites position overhead as well as a bar graph to indicate the signal strength of each. Satellite Geometry refers to how the satellites are positioned overhead. A poor reading may result if the satellites are clumped together in one area or arranged in a straight line. There is a signal strength indicated known as the DOP number. This stands for Dilution of Precision, the smaller the number the better the satellite geometry.
This is good to know in the event the equipment is not working or you question its accuracy. A quick check of the Status Page will let you know the strength of the signals being received as well as if the antenna is working.
The equipment also needs to be initialized. This means the receiver needs to find its position in the world if used for the first time, or if it has traveled a few hundred miles away from its home area with the power shut off. The receiver will usually do this automatically in a minute or two. If not, initialization can take place faster by locating the current position on its electronic map with a cursor, then press Enter. The current position will be indicated by a triangle shaped arrow icon. Cool…there you are, now your ready to go.
OK…now we know where we are. We have good batteries and satellite geometry, its time to take off. Using a special mounting bracket, the receiver is attached to the handlebars of our mountain bike, ready to hit some prime single track trails. With the unit on the Map Page, we see the arrow icon in the middle of the screen pointing to the direction traveled. The trail does not show up on the base map but you notice that dots are appearing where we traveled. This is the electronic bread-crumb trail. These dots indicate the exact previous position traveled. Pretty tough to get lost as long as the unit stays on, because you can always backtrack to the way you came. This method works best when there is another power source other than the only four AA batteries brought along. That is why waypoints are saved which will be explained later.
Still checking out the screen on the Map Page, we notice a couple of other indicators, speed and time of day. It’s nice to know how fast you’re traveling, a luxury on a mountain bike and it helps maintain the pace. A brief stop provides an opportunity to check out the other information the receiver provides. Scrolling through the pages there is a Position Page that tells you the following:
Indicator Status What it means
Compass NW 323° Traveling NW
Speed 0.0 mph Your stopped
Trip Timer 00:35 Started 35 minutes ago
Altitude 1245 ft Current elevation
Avg Speed 11.2 mph Average speed
Trip Odom 06.01 mi Traveled 6 miles
Sunset 07:35 Dinner time
Coordinates N 43° 45.240’ Latitude
W 122° 28.895’ Longitude
That is a great deal of information we have never had access to before. For this application we use the information to keep track of a number of things:
- Knowing where we have been allows the ability to backtrack to the starting point
- How far we traveled, how fast, and how long it took
- Time of day and even how much time left before it gets dark
Neat stuff but do not spend too much time looking at the screen while riding or driving, or your pals will use the latitude/longitude to tell the paramedics where to find the body. Keep your eyes on the road. Better yet have your passenger learn how to read this information so they can help you. In the scenario of our mountain bike outing, we check the information during rest breaks.