measure magnetic field

[TimTDP]

I wish to install a sensor with internal GPS Receiver and Compass to my boat
I am worried that magnetic fields, caused my vhf radio / antennae; boat electronics, battery charger, may effect the compass
I have a Samsung S21 smartphone.

How would I use the phone and Phyphox to monitor the magnetic fields? Sorry, I am not technically minded!

What is an acceptable magnetic field level to prevent compass deviation?

This is the sensor:
AS GPS HS - External GPS Receiver with Heading Sensor | Humminbird (johnsonoutdoors.com)

Thanks in advance

[Jens Noriʇzsɔɥ]

I would not necessarily trust the Samsung in this regard as the magnetic fields inside a smartphone are far greater than the tiny earth's magnetic field. The sensor is continuously recalibrated and I suppose that small differences are quite relevant for a ship's heading.

On first sight, https://boatingforbeginners.com/where-to...t-compass/ appears to give some reasonable recommendations on potential problems and where best to mount a compass.

Hope that helps a bit