Perigee and Apogee

[santy86]

Hi guys,

Do you know how to retrieve the Apogee and perigee height (from earth surface) ???

Thanks

Maybe this evening the INT-21 (my first add-on) will be released

 

[Ghostrider]

We don't say the "gee" thing here. We're adepts of the great Apsis.

 

[Urwumpe]

Hi guys,

Do you know how to retrieve the Apogee and perigee height (from earth surface) ???

Retrieve from where? Orbiters SDK? From the state vector of a vessel? Or by looking into Orbit MFD?

And yes: It is Apoapsis and periapsis unless you are interested into a special celestial body like Earth. So, if you are interested into the apogee of a probe orbiting mars, most sane people will tell you the apoareion (the apoapsis of Mars). Correct people might feel compelled to give you hints how to calculate the osculating elements of this probe relative to Earth and how to calculate the apogee of these osculating elements.

 

[santy86]

Sorry, maybe I was a not precise enough and, yes i ment Apoapsis and Periapsis retrieval from orbiter SDK. But it was just a question. No compulsory answer or explanation

Thanks anyway

 

[Urwumpe]

You have two options: Just retrieve the current Kepler elements by using "GetElements()". And work with the values of these. Or calculate these elements yourself by using the state vector (velocity and position relative to Earth).

When you have the elements, you can calculate apoapsis and periapsis distance. The next step for apsis distance is then subtracting the planet radius below each apsis. Thats simple for a spherical abstraction. And a tiny challenge when you use a WGS-84 ellipsoid.

 

[V8Li]

Variables used:

double ApA, PeA;
[SIZE=2]VESSEL *v;[/SIZE]

ApA:

[SIZE=2]OBJHANDLE hBody=NULL;[/SIZE]
[SIZE=2]hBody = v->GetSurfaceRef();[/SIZE]
[SIZE=2]v->GetApDist(ApA);[/SIZE]
[SIZE=2]ApA -=oapiGetSize(hBody);[/SIZE]

PeA:

[SIZE=2]OBJHANDLE hBody=NULL;[/SIZE]
[SIZE=2]hBody = v->GetSurfaceRef();[/SIZE]
[SIZE=2]v->GetPeDist(PeA);[/SIZE]
[SIZE=2]PeA -=oapiGetSize(hBody);[/SIZE]

v is the vessel, initialize it somewhere in your code using this line:

v = oapiGetFocusInterface();

before using it.

It really helps checking the API_Reference.pdf and reading other source codes from other MFDs, modules, etc.

 

[santy86]

Thanks a lot to all guys of this forum for the help given to me, that allowed me to finish my first add-on and to increase my interests in orbiter.

:speakcool:

Santy