Jupiter Red Spot Position and more

[Omega0]

Hi,

I would be interested in the position and the "appearing" of Jupiters red spot over many decades.
Here the first question is: What would be the best coordinate system?
Jupiters axis of rotation is very stable. So the latitude would be very interesting in my eyes.
But: How do we define the central point for the "spot" which in reality is something like an elipse?
In my eyes the easiest way would be to think of an elipse and we define the center as the crossing point between the lines of minimal and maximal diameter.
What would be the best measure for the longitude?
I think this is really problematic. In one picture I saw a nice Karman vortex street sourrounding the spot.
This is another word for: The spot is not rotating around the planet with the speed of the rest of the atmosphere in this longitude.
So my question: Is there data about the position of the red spot over time and how it is defined? The same for the "diameter" and the color range?

Thanks,
Jens

 

[andrew s 1905]

Is this any help http://www.projectpluto.com/grs_form.htm regards Andrew