Using a GPS Receiver Outdoors - Tips & Advice
Managing a GPS Unit in the Field
Handheld GPS units, as a rule, are tough devices designed for outdoor use. Most units are water resistant and can stand a quick dunk in a creek or the occasional jolt when you lose your grip. The upscale MobileMapper from Thales is completely waterproof (in one meter of water) and designed to take a fall onto concrete from 4.9 feet. Even less expensive units, such as the Garmin Etrex, are waterproof in a meter of water for up to 30 minutes. Regardless of what you paid or how rugged your GPS unit may be, it's wise to exercise basic caution.
Water
Basic models such as Magellan's eXplorist or Garmin's Etrex series can be used in a steady rain. Battery compartments form a waterproof gasket when closed. Rugged plastic bodies, tough shatter-resistant screens, and sealed controls do a great job of keeping out rain, sweat, and other sources of water.
A simple, relatively inexpensive method to further protect a GPS unit from water is to place it inside a sealed plastic bag. In a pinch, a sandwich bag will do, but a product such as the Aloksak will keep the GPS dry and allow you a clear view of the screen through the tough polymer plastic.
If you plan to take your GPS through white water, anticipate a prolonged dunking, or worry that the GPS may be accidentally crushed through falling or impact against rocks, Pelican makes a variety of tough waterproof microcases. When I travel outdoors, I also carry a handheld computer and folding keyboard, which I protect with a Pelican microcase.
Magellan eXplorist 200
Impact
In general , GPS units are tough and can take random abuse, but sustained impacts or a severe blow can disable them. I've stumbled and sent my GPS soaring through the air and crashing to the ground many times, but have yet to damage one that way. I have smashed a GPS screen by lunging into a trailside boulder while holding the unit. The unit continued to collect position data, though. A friend managed to drop his and then put his full boot-heel weight on the screen, resulting in a partially damaged display. But the unit continues to work.
Mountain biking renders some of the most sustained abuse. This is a function of how you carry the GPS, how skilled you are on the bike, and the type of ride. To lock on to and maintain signal reception, the GPS unit needs to be directly exposed to the sky. I've tried a number of methods to carry my GPS while grinding out single-track, and none are completely satisfactory. I've stuck the GPS beneath the Lycra of my bike shorts (on top of my thigh) with fair results. The unit stays put but is annoying against my leg.
If you don't mind acquiring bits and pieces of your route and then piecing them together later within a topo software program, place the GPS inside a mesh pocket of your hydration pack or riding pack. Inevitably you'll lose signal reception more frequently, and dropping waypoints will become a chore, but you can focus your attention completely on the ride while you are on-bike. I have an older Jandd hydration pack with a convenient mesh pocket on the outside designed to hold the head of a tire pump. My Etrex unit fits in there snugly and orients skyward, but waypoint dropping involves stopping and finagling the unit through the mesh.
The best way to secure a GPS unit to your person while road- or trail-riding is to mount it on the handlebar. Mounting units usually accommodate a specific model, so be sure you purchase the bracket designed for your GPS. The brackets hold the units securely but provide minimal protection from a tumble. A front shock dampens vibration and jarring, making it easier to read the screen on a bumpy ride.
Cold and Heat
All GPS units operate within defined temperature ranges, generally between 5°F and 150°F. Extreme cold can affect the unit when you use it outdoors; exposure to temperatures below the accepted lower limit may damage the unit. To protect it, keep it in an inside pocket close to your body (along with a set of spare batteries) and sleep with it at night. With most commercially available units, you will not be able to collect complete track data under frigid conditions, but you will be able to pull the unit out on occasion to fix your position, correct a bearing, or drop a waypoint.
According to experience gained by scientists living in Antarctica, extreme cold poses three common hazards. First, LCD screens will freeze if left exposed, rendering a unit useless. Units must be carried underneath clothing and close to the body, and should be exposed to the elements only for position fixes, not for continuous tracking. Second, battery life is greatly compromised. The consensus is that battery sluggishness in extreme cold is unavoidable. The solution is to use the least vulnerable battery, which is currently the lithium-ion cell. Third, bulky gloves require that large buttons be adequately spaced for ease of use, thereby minimizing user error.
Protecting the unit from heat is a bit easier: just don't leave it in a hot car, lay it on a hot rock, or store it under conditions that may exceed its maximum operating temperature.
Dirt and Grime
Hot lava on your GPS is a bad idea, but don't worry about getting it dirty. Much less caution is needed than with other electronics such as cell phones. A well-made GPS is akin to a nice hiking boot. You can get it wet and dirty, but, like a favorite boot, it should be dried and cleaned often. It'll last longer and be less likely to fail when you really need it.
Each manufacturer provides general information on proper care and cleaning of its GPS units. Wiping with a soft, damp cloth is usually enough, but refer to your owner's manual for specifics.
