Free GPS routes

Frequently asked questions

How accurate is a GPS? - Accuracy depends on the number and location of satellites in view. Don't forget that the view can be obscured, a GPS is designed to be operated (or at least to have its aerial) outdoors. It will not work underwater (!). It will be degraded or even lose all satellites from view under a dense forest canopy or in a deep ravine. In ideal circumstances accuracy is usually within a few metres. Accuracy can be compromised in some circumstances - the satellite signal should be "line of sight", in some conditions you may get a signal which has been reflected off another object. The effect of this is to give the GPS false information.

How reliable is a GPS? - Whilst the technology is long established, mature and reliable there are hazards. You should be prepared for the possibility that your GPS could let you down - in circumstances where you are critically reliant on the GPS you should have some kind of backup. Map and compass or even a knowledge of celestial navigation to get you out of trouble should the need arise.

Is GPS reception affected by the weather? - In general, no, it should operate under thick cloud and in rain fog or snow. Of course it is electronic equipment and subject to the shortcomings of any electronic device. Ingress of moisture (including a humid atmosphere) will affect and possibly stop operation. Extremes of heat or cold should be avoided (for example, most GPS units use a liquid crystal display, the display can freeze). I imagine a thunderstorm offers the potential for electrical damage.

How accurate is the compass feature of a GPS? - A GPS will give you two figures, a bearing and a heading. The bearing is the direction from your current location to the next waypoint. This will be quite accurate. The heading is your direction of travel, this is very unreliable at walking speeds. If you need to use a compass heading you should use a magnetic compass. Why? well the bearing may of little help in navigation if there are obstacles preventing you heading directly for your destination - and there often are - buildings, cliffs, rivers etc.

Which direction should I point my GPS? - It isn't a compass. It doesn't "point North". All that matters is the the aerial has "a good view" of the sky. It works out your direction of travel by looking back to the last set of coordinates it resolved from the satellite signals.

When I'm walking should I leave the GPS switched on or can I conserve battery power? - In clear country you can just turn on every few minutes to get a fix on your current location. Where the signal may be degraded it is better to leave it switched on, that way it will make best use of any signals it does capture. If you switch on in an area of poor sky visibility it will struggle to capture any signals. If it has an image of where the satellites should be and individually some drop out of sight then even one signal will be of some use.

My GPS "only" tracks up to 12 satellites, is that enough? - 3 satellites are sufficient to triangulate your position in 3 axes, tracking 12 helps with location should one of the essential 3 be obscured. There are GPS receivers which attempt to track 18 satellites. The benefit will be very marginal. I have never seen my 12 channel unit actually getting simultaneous signals from more than 8 satellites.