Putting Emergencies First on Your GPS List

GPS phones and receivers are becoming less expensive. And this means you can now purchase high end GPS devices at relatively low prices. If you’re concerned about quality, reliability and features, though, you have to watch out. You don’t want to purchase a GPS device that fails you in an emergency.

One of the first things to consider for a GPS device is battery operating time and the GPS device’s temperature range. Most batteries give out after 20 hours, so you’ll always want to pack a few batteries or a solar battery charger. Or better yet, get a solar powered GPS unit.

However, more importantly, check the operating temperature range of your GPS device. The last thing you need when lost at sea on a cold night, is a GPS device that is giving you unreliable readings. That’s right, once a GPS device is out of its operating temperature range, it still may work, but there is a high chance that the location data it gives you is incorrect data.

Once you have thought out and researched the safety concerns about GPS, its time to consider the latest technology features. Today, just like cell phones, you will find handheld GPS devices that have cameras and a wide range of software already built in.

Also consider the size of your unit and the application. Today you can find not only a wide selection of cell phone sized GPS units, but also GPS wristwatches that are not only waterproof but also ruggedized.

Today’s GPS devices offer more computing power than ever. And so just like computers, consider amount of onboard GPS memory and the GPS microprocessor or microcontroller used (or the GPS chip set used). Also look for ports, such as USB ports and ports for plug in cards. Plug in cards allows your GPS devices to access more maps and permit your GPS device to run advanced navigation software. Furthermore, add-on cards can be even used to improve the performance and accuracy of your GPS devices.

A common question most people have about GPS is its location accuracy. So how accurate is the location your GPS device provides? The answer is not as simple as it might seem. GPS location data is not an absolute. It’s probabilistic. For example, if your GPS device informs you are at the junction of the Mississippi and Missouri rivers, it really means there is a high probability you are there.

Just how probable you may ask. That depends on the probability rating of your GPS device. GPS manufacturers publish four different probability specifications, often referred to as accuracy specifications These accuracy probability specifications include Circular Error Probable (CEP), the first deviation Root Mean square (rms), the second deviation Root Mean Square (2drms) and third deviation Root Mean Square (3drms).

So how do you interpret these accuracy specs with respect to your GPS devices? First look at the accuracy specification used. If your GPS device is a CEP rated GPS device, the location the GPS device displays has only a 50 percent chance of being true. Similarly, if it is a drms GPS device, there is 68 percent chance the reading is true. For a 2drms device, there is a 95 percent chance of a true reading and for a 3drms device, a 99.7 percent chance of a true reading.

Next, look at the distance specification that is given with the accuracy specification. For a CEP device this may be, for example, 3 meters. So for such a CEP device there is a 50 percent chance that the location displayed is correct within 3 meters. Conversely, there is 50 percent chance that the location given is not within 3 meters of the displayed location.

However this only touches the surface about accuracy. There is a lot more about GPS accuracy. So if you plan to use GPS as an emergency support device, study GPS technology in detail and ask lots of questions.

Furthermore, if you have not already done so, consider a course in statistics and probability. GPS accuracy specifications are based on the concept of standard deviation, which is fundamental to statistics. And while you’re at it, study boating safety statistics. In this way, you will be able to maximize the probability that you will not only have a safe boating trip, but also have the safest GPS device on the market.