IFR Charts: ATIS vs ADSB Altimeter Settings?
Joined 05/14/2017 - 1 Posts
Answered By AOPA
On many IFR approach charts they state "Obtain local altimeter on CTAF; when not received use an "alternate" airport altimeter setting.
Can I  legally or safely use the Altimeter reporting from my ADSB receiver (G1000) or Foreflight  or am I required to look up the alternate airport Atis frequency,  which is not published on the chart , then wait to hear the current readings?
2 Replies
Joined 01/30/2020 - 38 Posts
AOPA Staff Answer
Interesting question. I can find nothing that states that you couldn't use the altimeter setting obtained via FIS-B to provide the altimeter setting that you're needing to shoot this approach. It can vary slightly from what is reported on the automated weather, but not by much. When using a Remote Altimeter Setting Source (RASS) there could be some difference from local as well, which is why the minimums are usually higher when utilizing one. As always, you'll want to ensure the weather you're using is current and not several hours old.
Joined 06/11/2017 - 699 Posts
Considerations in making this decision...

ATIS information is often up to one hour old, and may be up to two hours old.  AWOS/ASOS radio broadcast information is up to the minute.  FIS-B information may be 20 minutes to one hour old -- you have to check the issue time in the METAR block to know for sure.  Try to use the most recent information, especially if conditions are changing, like when a front is coming through.