subject: Wristwatches With Altimeters - Compass Performance Explained [print this page] When you're talking about watches with altimeters there are a number of different gadgets and features you can get on the watch. It's almost amazing how many things they offer nowadays. As the competition heats up there is more pressure to add more and more things. You got to make sure though that is things that you get you understand how to use.
It's fairly uncommon to see a watch with altimeter function that doesn't also have a compass. The reason for that is most of the watches are intended for outdoorsmen and the compasses are a pretty essential part of any outdoor trek.
The technology that underlies the compass part of the watch was developed by the government for use in military operations. It is electronic induction process that drives the compass function.
What you have got to keep in mind is the number of things that can disturb the function of a compass. There's just a lot out there that can fool the compass and thinking is pointing to magnetic North when it is not. You need to take the time to read the owner's manual and make sure you understand how to take a compass reading and don't just assume that you know how. There are too many ways to mess this up by being sloppy.
Now, you need to keep in mind to there's a big difference between True North and Magnetic North. As a matter of fact there is approximately 11 1/2 difference.
Another big cause of error in the compass is how you hold your arm. It must be perfectly level properly. It doesn't have to be perfect but you need to make an attempt to keep your arm level when taking the compass reading.
You also need to keep in mind that the last compass direction used is probably what you'll find when you reactivate the watch. What happens is the compass goes in sleep mode after use in order to conserve power. Therefore, when you wake the watch back up to read it again it will read the last setting. You just need to remember that so you don't think you are reading the current direction of travel.
Calibrating the compass function on watches with altimeters must also be done at regular intervals. The way to do that is when the batteries are changed. That is the best time to reset any of the watches functions to factory settings.
In the final analysis it's a good idea to let your watch function be the backup for your primary instruments like your main compass. When you're on a hike and you are far away from civilization and possibly out of cell phone range, it's a comforting feeling to know that you hav got back up protection for your primary instruments.
