How Make a Simple Altimeter?

I’ve been over all the other altimeter and speedometer questions and answers thoroughly and am still in need some help.

I need a very simple altimeter.
It needs to be dial on a gameObject and not GUI.

I have a needle and a face.

All that I need it to do is have the needle be placed at 0 when the altimeter is at zero and move accordingly and accurately as you ascend and descend.

I can access the altitude variable which is easy enough and works fine.

I think I need to use something like this:

float needleAngle= Mathf.Lerp(altitudeLow, altitudeHigh, Time.time);

Although Time.time is wrong.

I need to Lerp the needle using the altitude.

What am I missing and how do I do this correctly?

Thanks in advance!

float needleAngle= Mathf.Lerp(altitudeLow, altitudeHigh, actualAltitude/(altitudeHigh-altitudeLow));

Although if you want the altitude needle to move based on angle then you probably want something like this

float needleAngle= Mathf.Lerp(angleMin, angleMax, actualAltitude/(altitudeHigh-altitudeLow));