Google Earth Maths Question; How many metres wide is my image?

This question is about Google Earth, but the question would probably apply to other applications: its a basic maths question which I need to code some tools for the students... Here goes with a simple example. Given a view:

longitiude = 48.197433°
latitude = 16.352953°
distance = 240m
heading = 0
tilt = 0

How to calculate what the screen image represents in terms of projected geometry? That is say I want another view and move the viewer one screen and exactly one screen to the right? Now my guess is that I need to convert all geometry to the same measure throughout (say metres) and then do the maths.... but I am just guessing from first principles never having done any 3D calculations before.

First working out what the screen pixel geometry is in metres is not so straight forwards i believe. That is it is not simply 72 dots per inch...

Then once everything is worked out in metres - then what? Again at a guess I'd figure we had a point in space 240 above the surface and a flat plane (the screen) at some distance from this point with the corners of this screeen image projected down on to the actual points on the curved surface of the globe. I don"t really trust any of this to get me pixel accurate results... comments welcome!

Aggregation

This is not aggrevation but aggregation .

Here we are looking at how to take blogs from studios, individuals (students, designers, professors etc), and integrate them into a publication (ArchiTex.Tv) such that additional features can be added to that which any individual blog can achieve.

In particular we wish to explore the benefits of group or peer review. The knowledge architecture should allow both individual views, and collective or shared views. In simple terms an individual view is that individuals blog, while ArchiTex.Tv seeks to create shared views.

The issues here are how - both technically, epistemologically and pedagogically.