magnetic compass 
noun
Another term for compass (sense 1 of the noun).A magnetic compass should always point north; a moral compass should always point out what is moral - and immoral....
- Divided into two groups, the contest saw one of the team groups stay at the baseline to help solve the clues while the other group used a magnetic compass to get the right direction.
- Each lava unit was sampled, usually as seven independent cores, drilled over several metres of outcrop using a portable motor and oriented by sun and magnetic compasses.