A GPS receiver, for our purposes, is a small hand-held electronic device that receives multiple satellite signals to determine its position pratically anywhere on the globe. Further detail The accuracy of GPS receivers varies depending on a number of factors, including time of day, weather, obstructions (trees, buildings, etc.), satellite geometry, WAAS signals, and more. Many geocachers allow their GPSr to get them close to a target, and then use The Force to guide them the rest of the way.
Units prices can range from a under $100 to more than $500.
Selecting a GPS for Geocaching
The bare essentials for a GPS unit (GPSr) used to hunt a geocache are: (1)the ability to input and display user coordinates to three decimal places for the minutes, and (2)the use of WGS-84 (NAD-83) datum. While some have successfully hunted caches with units that don't meet these minimums, they do have some difficulties. All consumer grade units sold in the last few years will meet these minimums.
Can't Live Without
Be careful of the most inexpensive units because they do not include a data cable that hooks up to your computer. You will want a data cable to reduce time entering coordinates and errors inputing them manually. Many a new cacher, and even experienced, has been frustrated when inadvertantly entering the wrong coordinates.
Another nice feature is mapping screen. The map will give you an overhead map that helps you get your bearings. Most modern units will have some sort of mapping screen. This is not to be confused with a mapping unit which will have detailed real-world maps includes roads, rivers, and more.
Another nice feature is a bearing pointer (arrow navigation) screen. This screen indicates the direction and distance to your destination coordinates. Usually, "up" can be configured either to north or to the direction you are currently travelling. GPSr devices designed for car travel may not have this feature.
Most mid to higher end GPS units allow you to add real-world maps of different flavors to your units. The types of maps can be detailed roads and streets, topo maps with detailed topographical features, or both. The area your unit can hold is determined by the amount of data that will fit in the unit's memory. Some units have removable memory so you can use large data sets or swap smaller ones out for others.
Autorouting units will give you turn-by-turn directions from the present position to a destination you select. This can be extremely helpful in geocaching to go you from the parking area of your last find to your next.
Units that don't have a built-in magnetic compass rely on the movement of the unit to determine direction. Thus, when you are sitting still, it has no clue. When you stop and turn in any direction, the unit cannot tell you which way to proceed until you start moving again. An electronic compass will tell you which way the unit is pointed regardless of movement. Some cachers forego the electronic compass for a good magnetic compass because the GPS-based option is more expensive than a good old-fashioned magnetic compass. Packing a manual compass is good advice anyway, in case one's GPS fails.
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