True North Orientation

For my postcode/zip code in July, 2021, magnetic north was estimated to be 0 deg 36 min west of grid north (British National Grid). If I buy a decent compass that displays magnetic north, what would my offset be for true north?

Cheers, Neil

If you have an Android phone you can use an app such as GPS Test ( and it will display the declination to you on the compass screen. It also allows tapping on the compass and having it point to magnetic or true north.

For iPhone there may be such apps as well.

This one ( from the same developer has the true/magnetic option by clicking on the gear icon in lower right corner

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In addition to what @chants92 suggested, you may find that using the satellite view on the map app on your device easier to use. Just use it to find a land mark true North of your Tempest sensor location you can use to site on.


Google maps works great as an alternate method for eyeballing an overhead view and getting very close rather quickly.

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I took a snapshot of my location within Google maps and drew a vertical/northward bound line from my house. Does the Google maps compass point true north?

yes it does, look here Google Maps (magnetic is about 22 degrees off)

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I use this app to determine true north

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