1
$\begingroup$

enter image description here

Extension area(E airspace) shown as shaded magenta start from 700AGL but how to measure 700AGL over the water like in this picture? Cuz there’s no land…

$\endgroup$
2
$\begingroup$

While the documentation uses AGL when talking about class E airspace the chart legend uses the slightly different phraseology of

above surface level

enter image description here

This avoids the ambiguity of, ground or ocean.

Interestingly the glossary uses both ground level and sea level but explicitly defines neither.

$\endgroup$
  • $\begingroup$ Now I get it! Thx for your explanation. $\endgroup$ – Steven Ryu Feb 11 at 23:20
0
$\begingroup$

When you are over the water that’s actually the easiest to measure. If you are over the water 700' AGL will read 700' on your altimeter. It’s when you are over land that it gets harder.

If you fly with something like ForeFlight you can set one of the display boxes on the bottom of the screen to show height above terrain, but otherwise you just have to use your judgement.

$\endgroup$
  • $\begingroup$ Nit: That should say over the "ocean". Lakes and rivers inland (also "water") can be much higher. $\endgroup$ – StephenS Feb 3 at 3:54
  • $\begingroup$ @StephenS True, but in his example water and ocean are the same thing. $\endgroup$ – JScarry Feb 3 at 15:16
-1
$\begingroup$

Looks to me like the chart is showing controlled airspace as 100/60, 100/50, 100/40 - which means the highest you can go is 4000, 5000, 6000 feet MSL and stay clear of the Class C, not AGL. So the height would be read off the airplanes altimeter. Go to www.skyvector.com, enter HAF at the top left, then select San Francisco. To the left of HAF is the explanation showing T/30, and 70/30 - in MSL.

$\endgroup$
  • $\begingroup$ You misread the chart. Starting at the inner ring the Class Bravo starts at 4000 and goes up to 10000 MSL, then 5000MSL, and then 6000MSL. $\endgroup$ – JScarry Feb 3 at 3:29
  • $\begingroup$ Yes, you're right. Updated my answer. $\endgroup$ – CrossRoads Feb 3 at 3:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.