Scipy / Numpy Reimann Sum Height
For computing Reimann sums you could look into numpy.cumsum().  I am not sure if you can do a surface or only an array with this method.  However, you could always loop through all the rows of your terrain and store each row in a two dimensional array as you go.  Leaving you with an array of all the terrain heights.
I am working on a visualization that models the trajectory of an object over a planar surface.  Currently, the algorithm I have been provided with uses a simple trajectory function (where velocity and gravity are provided) and Runge-Kutta integration to check n points along the curve for a point where velocity becomes 0.  We are discounting any atmospheric interaction.
What I would like to do it introduce a non-planar surface, say from a digital terrain model (raster).  My thought is to calculate a Reimann sum at each pixel and determine if the offset from the planar surface is equal to or less than the offset of the underlying topography from the planar surface.
Is it possible, using numpy or scipy, to calculate the height of a Reimann rectangle?  Conversely, the area of the rectangle (midpoint is fine) would work, as I know the width nd can calculate the height.