Every new location will have a different geomagnetic field, as well as other external influences.
A magnetic field sensing compass should ALWAYS be swung in a new location, possibly even before every event in the same location - a relocated tool bag will have an effect - within reason.
It doesn't take long and is very easy to do.
Be aware of external magnetic interference - i.e. large underwater power cables in shallow water WILL influence your compass/swing. Same for large shipping container terminals.
Therefore your compasses internal 'deviation card' will no longer be valid as you move away from those magnetic influences.
The racing area near Cape Town Harbour entrance and the Solent between Gurnard and Osbourne Bay are two prime examples where a swing may result in errors in compass readings due to sub sea cables.
Every new location will have a different geomagnetic field, as well as other external influences.
A magnetic field sensing compass should ALWAYS be swung in a new location, possibly even before every event in the same location - a relocated tool bag will have an effect - within reason.
It doesn't take long and is very easy to do.
Be aware of external magnetic interference - i.e. large underwater power cables in shallow water WILL influence your compass/swing. Same for large shipping container terminals.
Therefore your compasses internal 'deviation card' will no longer be valid as you move away from those magnetic influences.
The racing area near Cape Town Harbour entrance and the Solent between Gurnard and Osbourne Bay are two prime examples where a swing may result in errors in compass readings due to sub sea cables.