[GRASS-user] Interpolation method for parallel samples

[Markus Metz]

On Mon, Jan 5, 2015 at 11:51 AM, Martin Album Ytre-Eide
<Martin.Album.Ytre-Eide at nrpa.no> wrote:
> Thanks for your answer Markus!
>
> Here are my thoughts and trials:
>
> The normal screen output when running v.surf.bspline looks something like this:
>
> Reading values from attribute table...
> Initializing output...
>  100%
> Load masking map
>  100%
> Processing subregion 1 of 25...
>   90%
>
> ##
> ..but when running with  ew_step=50 and ns_step=1000, I get:
>
> Reading values from attribute table...
> Initializing output...
>  100%
> Load masking map
>  100%
>  100%
>  100%
>  100%
>   10%

Oops.
>
> ... and it does not seem to finish at any point.

That is a bug. Can you please open a ticket for this and add an
example using the North Carolina sample dataset? I guess this bug will
appear with any input data as long as ns_step and ew_step are
sufficiently different.

Markus M


>
> Even setting the ew_step=90 generates the same behaviour.
>
> My result with 100 and 1000 is not that bad actually - I might say I'm happy with that.
>
>  I am experimenting with v.surf.rst, but for some reason it ignores a lot of points (to dence). I also don't know if I understand the theta and scalex parameters. For me, it seems they are optimizing the results from a "feature" that is anisotropic. Does this "feature" in my case mean my area with samples that I wont to interpolate? My area is somewhat rectangular - being about twice the size in the nort-south direction, but my data - as I mentioned , are spaced by 50 m in the e-w direction and 1000 m in the n-s directions. So what combo of theta and scalex should I use?
>
> Thanks!
>
> Martin
>
> _______________________________________
> Fra: Markus Metz [markus.metz.giswork at gmail.com]
> Sendt: 17. desember 2014 22:11
> Til: Martin Album Ytre-Eide
> Kopi: grass-user at lists.osgeo.org
> Emne: Re: [GRASS-user] Interpolation method for parallel samples
>
> Martin Album Ytre-Eide wrote:
>> Hello!
>>
>> I have airborne gamma measurements obtain in lines. The spatial distance
>> between the 'points' along the line is 50m (e-w direction) and the spatial
>> distance between the lines is 1000m (n-s direction)
>>
>> I am currently experimenting with the v.surf.bspline function - setting
>> ew_step=100 and ns_step=1000. I am having trouble setting the ew_step any
>> lower.....?
>
> What exactly is the trouble with setting ew_step any lower? In theory,
> it should be possible to set ew_step to any value.
>
> Markus M
>
>> I am also using the smoothing parameter lambda_i.
>>
>> If anyone have some interpolation tips with this type of data - I would be
>> happy to hear about it.
>>
>>
>>
>> Martin
>>
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