True Alt

gistfile1.txt

public double TrueAlt()
{
    Vector3 pos= this.part.transform.position; //or this.vessel.GetWorldPos3D()
    double ASL = FlightGlobals.getAltitudeAtPos(pos);
    if (this.vessel.mainBody.pqsController == null) { return ASL; }
    double terrainAlt = this.vessel.pqsAltitude;
    if (this.vessel.mainBody.ocean && terrainAltitude <= 0) { return ASL; } //Checks for oceans
    return ASL - terrainAlt;
}