Re: About isostatic computation and -N+l (gravfft)

On 14-11-2013 18:26, Gabriel Dragone wrote:
> Hello,
>
> I have a doubt concerning the isostatic calculation done by gravfft 
> (-T). Using, for example, Te=0 and a compensation depth (-Z) of 35000 
> m, I would expect that all topography had its root bellow 35000. 
> Nevertheless, since -N+a is set, the response is a fluctuation around it.

The FFT method (Parker's), after detrending,  implies that the solution 
is 'waves' about zero but there is one term in the equation that 
represents the average compensation depth (that's what -Z does). So 
naturally your solution should be about the 35 km depth (parts above and 
others bellow). Isn't that what you get?


> Is there a way to avoid the demeaning? Setting -N+l does nothing, so I 
> don't know whether this is a bug or if -N+a is really needed.
>

The man says "-T implicitly sets -N+a". This is for better convergence 
of the Parker's method'

Joaquim

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