Satellite positions are accurately defined using Two-Line Elements (usually shortened to TLE). Wikipedia has a pretty good discussion here:
http://en.wikipedia.org/wiki/TLE
Since they are in continual motion, a TLE allows predictions of future position to be made with decreasing accuracy over time.
I would suppose that positions on other planets could usefully be specified by latitude, longitude and elevation above (or below) a recognised mean. For 2D objects, a set of points would suffice; for a 3D structure a set of vectors from a defined point.
Interestingly, no-one has bought up the idea of a time axis. There's a tree outside my house which will be removed in about 4 months, so if I want to chart changes in my local environment knowing when the tree was, or was not present would be necessary. Likewise for sensor observations. To know that the temperature is 31.2 degrees C is fine, but knowing exactly when it was at that value tells me far more and potentially allows me to chart temperature changes.
Hook
On Thu Jun 14 15:56 , stephen white <[EMAIL PROTECTED]> sent:
On 14/06/2007, at 2:17 AM, brian grant wrote:
> my proposal for a recursive geospatial reference is this: a modified
> Hierarchical Triangular Mesh (HTM) - please bear with me on this -
> I need to
OK, I'm answering because you asked. I looked into that kind of
addressing when I was wondering how to locate my data, but concluded
that it was a case of premature optimisation. It is indeed more
efficient to store co-ordinates in that form of representation, but
it is also a form of compression where it is more difficult to work
with the numbers.
What concluded the argument for me was the observation that any form
of representation that is inherently based around a globe is not
going to be suitable when we're trying to locate points that are not
on the globe. How do you represent satellites in space? How do we
locate other planets when we start colonising the moon or Mars?
Despite the problems, latitude and longitude is "good enough" - there
would have to be a significant advantage to make it worthwhile to
overcome the default inertia. What specific improvement does HTM (or
Geotude) bring to the table that latitude/longitude cannot be
modified to also handle?
So yes, I would have to agree with Richard Abas that it is a solution
in search of a problem. :)
Steve.
--
[EMAIL PROTECTED]
_______________________________________________
Geowanking mailing list
[email protected]
http://lists.burri.to/mailman/listinfo/geowanking
)
_______________________________________________ Geowanking mailing list [email protected] http://lists.burri.to/mailman/listinfo/geowanking
