GPS Units Explained By Me

I get a lot of questions about GPS units, normally I just tell people to do more research using the Internet. I have decided to try and explain the units in my fashion. I still feel you can gleam a lot of information by doing some research, so do that also. A GPS unit is nothing but a computer which has a special chip in it which can receive and pass on satellite information to the GPS computer. The GPS computer uses the satellite data to determine the latitude/longitude (lat/long) where the GPS unit is. It would be nice if it could actually calculate the exact lat/long, but that is not possible. It gets as close as it can and uses that. There are two reasons why it can not calculate the exact lat/long - 1. The Defense Department does not allow manufacturers to do it - they say for national security 2. How good the unit is receiving satellite data - that mainly depends on the quality of the special chip in the unit and the type of antenna in the unit. You can not do anything about #1, but #2 lives by that old rule - the more you pay, the better the reception. Currently the buzz words are "high-sensitivity chip" and" external antenna". Garmin uses the "X" in their model numbers to reflect that the unit has a high-sensitivity chip. Sadly, there are cheaper versions of this chip being put in units, so you just don't know. What the high-sensitivity chips and external antennas provide is better reception in the woods and on cloudy days, thus better accuracy. If your using the unit for hiking, accuracy can be a little more lax then if your using the unit for say, GEOCaching. Some units have a feature called "WAAS" - it is designed to improve accuracy. Do a Google search on it if you want to know more about it. If your unit has the feature, turn it on - it does use more battery life, but not much. Now the fundamentals of all handheld GPS units
  • Waypoints - locations or landmarks stored in your GPS for reference. All GPS units allow you to "mark" a position which you may want to return to or you may want to go to. A classical waypoint is the place you parked the car, so if necessary you can find your way back to it. Another waypoint might be a place on the trail you want to remember, say were you got water. Most units can store upwards of a 1000 waypoints, so use them. You can use the "find" function of your GPS to see any waypoints recorded in your unit. That is why it is very important to give new waypoints a logical label - like "parking". Thus if you had to get back to the parking area, you would be able to recognize the label in the waypoint list.
  • Tracks - "breadcrumbs" recorded by the GPS unit of where you have been. Tracks are actually stored in the unit as "points". Each point is an individual database record containing all kinds of data about the spot that the recording was made - mainly the lat/long and time. Each point is like a waypoint, but it is recorded by the unit instead of you. Imagine if as you hiked along you had to push the "mark" button every 3 feet or so, well the unit is doing that for you - just storing the data in a different place. The track points are displayed as a line on maps, but that is just the software connecting the points (that is where the time comes into play).
  • Statistical data - this referred to as "trip data". All kinds of information is stored about a trip - moving time, stopped time. average speed and much more.
The main problem with all the units I have been exposed to is they do not allow multiple trips to be stored in the GPS unit. They store all the data, but they do not allow you to store each trip's data separately. So, lets say you go on two hikes and don't reset the data between each trip - when you get home and download the data to the computer all the waypoints will be mixed together, the tracks will be separate (as long as you turned the unit off between each trip), but a little confusing. The "trip data" will reflect just one set of totals - so you will not know say the time of spent on each trip. Waypoints and tracks can be split out pretty easily, but trip data can not. The only way I know of to get around that is to write down the trip data after the first trip, then reset the trip data to prepare for the second trip - do not reset the waypoints and tracks until you have downloaded then to your computer. Of course, if you don't care about the historical value of the the waypoints and tracks, than you could reset them also before the second trip. I always save my trip data to my computer before resetting them. So, learn how your unit handles waypoints, tracks and trip data. It is not necessary to know that much about lat/long - just be aware that every spot on earth has a unique lat/long and it's your GPSs function to determine the current lat/long. As I mentioned the before, your GPS unit can be used to take you to a recorded waypoint. Lets say you get lost and want to get back to the parking area. Assuming you created a waypoint for parking and labeled it well - just use the "find" function to find it in the list of waypoints. Then select "goto" and the unit will point directly at the parking area. This is "as the crow flies", you are not a crow, so you must work you way back using trails, paths etc. You have to use common sense when using the "goto" function, don't' go into a "bushwhack" mode - use logic to get back to the parking area. A feature seldom used is called "trackback". This function actually tells you exactly how you got to a spot and how to back out of it if you are lost. Each unit handles this differently, so read your manual and become familiar with this function. FYI - GEOCaches are just waypoints to your GPS unit - they have an icon which is used by some units to handle them in a special way. So, my rules are
  • Record a lot of waypoints
  • Download and save your data
  • Keep your unit clean - reset everything after every save or trip
Look at my other entries on GPS units for more information.

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