Magnetic? or True?; AGL? MSL?

As you may know that the true north is different from magnetic north – true directionmagnetic direction. Then when we look at the charts and weather report/forecast, or when we hear the information form the ATC controller, whether these information is based on true or magnetic direction?

Similar question is that when we look at a chart, whether the cloud base or sort of information based on AGL or MSL?

To be honest, I was struggling about this. Therefore, I would like to make this special post to consolidate the knowledge.

 

True direction or Magnetic direction

  1. Runway designation marking (the runway number) is referring to magnetic north
  2. Wind spoken by ATC/ATIS (broadcast by radiotelephony) is referring to relative to Magnetic north (°M)
  3. METAR wind is reffering to True north

 

AGL or MSL

  1. AGL for any information related to A/D (e.g Cloud Base @ METAR)
  2. MSL – for the other information

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