Andrew Sarangan writes:

So what instrument would you suggest we use for true headings?

A combination of INS and GPS would work. It would be at least as
accurate as a compass.

This could be cross-checked against a magnetic heading internally as
long as the exact location of the geomagnetic poles are known.

An ANS could give you true heading even standing still.

GPS does not give you true heading; it can only give a true course. You can't
reliably use a GPS for verifying your runway heading.

As soon as you move, GPS can give you a heading, and an INS can
maintain it for you.

GPS headings only work when you are in motion. Remember the Comair
accident? I suspect such accidents will increase if we switch to GPS
based true headings.

How you navigate with true headings is irrelevant here; the important
thing is that true headings never change.

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