KSP Altitude Calculation Inquiry

[Luuko]

Out of morbid curiosity, we know the altimeter provided in stock KSP is Mean Sea Level MSL, not above terrain. To get Above Ground Level (AGL), how would we go about doing this? Do we calculate AGL akin to how we convert between earth's MSL and AGL via comparing them against the WGS84 model (A rough geoid measurement of earth's surface) or are should we measure from the center of mass of the vehicle and straight to the center of the sphereoid and note just where it stops and how far/long the distance is? Thoughts?

[NathanKell]

In IVA, you already get a radar altimeter. It plots your vessel altitude above whatever terrain is directly under you (including if the terrain is below sea level).

[Headhunter09]

KSP doesn't model the geoid, so sea level altitude is given via a set radius from the center of the planet (to the transform of the root part of the craft). Radar altitude is done by raycasting straight down (I think).

[sarbian]

That or by asking the terrain system the terrain altitude under you.

[stupid_chris]

Raycasting is slow and not very accurate. You can get the terrain altitude directly below your ship with Vessel.pqsAltitude. Something like this would get it right and be much faster.

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;
}

[Luuko]

Hrm. Well that gives me a few points to consider at least.

To clarify, work has me doing some geopositioning big data stuff and I saw a possibility to try to understand how one might handle such in KSP. Thank you for your time and consideration.

Edited February 20, 2015 by Luuko