It is important to ensure that your GPS has sufficient battery before using in the field and spare batteries should always be taken. GPS may not be suitable in all scenarios such as bad weather or in areas obstructed by hills or buildings, so a compass clinometer should always be taken as well as a backup.
If the GPS hasn’t been used for a while, or the batteries have recently been changed, it is a good idea to calibrate the compass. This should be done outside, away from objects that could influence magnetic fields, such as buildings, vehicles or overhead power lines. On the compass page of the GPS, there should be options to calibrate the compass and this is usually done by following the on screen instructions and rotating the GPS a few times.
Check the settings of the GPS to see which north is the reference north. This should be set to ‘true north’. You should always write in your field notes which north you are using.
Most GPS compasses will rotate to indicate which direction you are facing. You can lock a direction of travel and the compass will show an arrow to keep you going in that direction. For example if you want to travel north, rotate yourself and the GPS to face north (or 0° bearing), lock the direction and follow the arrow on the compass to travel north. There may also be options project a waypoint, i.e. to set the distance, for example if you wanted to travel 1km north, you could lock the direction to north and set the waypoint distance to 1km and follow the compass arrow.