poisson_grid_fill

Hello NCL-talk,

I am attempting to use poisson_grid_fill to fill in some _FillValues on a DEM of the Eocene. These areas are supposed to be continental interior basins that are below sea level.

My understanding is that the function does not modify the real data, and only uses these values bounding the _FillValue to calculate changes in the potential fields.

First attempt: surrounding basins are above sea level: result is a topo graphic low that is above sea level.

Second and subsequent attempts: subtracting (in multiples of 10m) from the total topography to create a boundary around the _FillValues that is below sea level.
Result: the _FillValue are filled in below sea level, but as opposed to creating a 'basin', instead the function 'bends' back towards the surface and essentially asymptotes toward 0. The picture is essentially a 'inverse' crater (see attached).

I figure a good start is for me to look at the calculation of poisson_grid_fill. I am trying to find the source code, however, I don't know where it is.

Can someone point me toward it?

Does someone know what I am doing wrong (relevant code below)?

Thanks,

Jonathan R. Buzan
PhD Student; Earth, Atmospheric, and Planetary Sciences
Purdue University
550 Stadium Mall Dr.
West Lafayette, IN 47907
jbuzan@purdue.edu

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;fi2 = input dataset
is_cyclic = True
guess_type = 0
nscan = 1500
epsx = 1.e-3
relc = 0.6
opt = 0

poisson_grid_fill(fi2,is_cyclic,guess_type,nscan,epsx,relc,opt)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

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