Plotting orbit ground track relative to a given point

[Hlynkacg]

Thank you for all the assistance thus far, but I have a second related question.

How would I go about calculating the position of my Periapsis? IE i would like to predict the result of the "GetRelativePostion" with respect of my reference body function at time of Periapsis.

 

[indy91]

If you really only need the position vector at periapsis then you can use the [ame="http://en.wikipedia.org/wiki/Eccentricity_vector"]eccentricity vector[/ame], which points in the direction of periapsis. Just calculate the magnitude of the periapsis radius and multiply it with the unit vector of the eccentricity vector and you have your periapsis position.

If you want a general solution to predict your state vector in the future, then it gets a little bit more complicated.