[GRASS-user] OFF-TOPIC - Earth Curvature in profiles

[Hamish]

Carlos wrote:
> Sorry for the OT, but can anyone point me some reference (paper, web,
> etc) that explains how can I draw a topographic profile using the
> Earth´s curvature? I am thiking about the output of r.profile (ascii,
> distance from origin + elevation), in a section of about 3000 km,
> with a vertical exaggeration of about 200 times.


maybe a little work, but consider elevation as radius perturbation and
distance along transect as theta-angle, then draw a circle with the
relief shudder in it. ie like an AM radio wave.

when that is working you can change the ideal circle to an ellipse of
appropriate bend for 3000km.


but probably it is better to just figure a way to calculate the
vertical distance between a chord connecting the two 3000km ends and
the circumference for each step along the transect. 

then add that distance to the elevation.


just an idea,
Hamish



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