[GRASSLIST:5966] Re: v.surf.idw (point in region!!!)

[Massimiliano Cannata]

Hi Paul,
I try to better explain me.
In the grass version I have (grass-6.0.0beta2) when I interpolate a 
vector point file by using v.surf.idw (with or wothout the -n flags) the 
points that are not in the current region are not considered.
What I want is to consider also the points outside the region to 
generate the interpolated map.

I understand that it is not possible to consider them (poin out of 
region) by using the index point because they doesn't fall in any cell 
(otherwise segmentation fault happens!) but with the old method (not 
index cell) it is possible to consider also point out of region.

What I simply modify in the code is to add a -a flag that causes the use 
of old method (not index cell) with all the points in surface 
computation. All the rest is still the same.....

I'm I in wrong?
Let me know.
Ciao,
Maxi



Paul Kelly wrote:

> On Wed, 2 Mar 2005, Massimiliano Cannata wrote:
>
>> So, I've applied the change and things seems to work now.
>> In attachment i post the modified main.c file.
>> Hope it can be usefull.....
>>
>> Maxi
>>
>> Massimiliano Cannata wrote:
>>
>>> I see that in function new point (line 372) the author exclude 
>>> points outside the region due to segmentation fault cased from new 
>>> cell index solution.
>>
>
> Not sure what you mean here---in the new method the points are indexed 
> according to which cell they fall into. It is not possible to index 
> points that are outside the current region in this way (because they 
> don't fall inside any cells) and so they are not included.
>
> The -n flag doesn't index the points at all; it just uses all the 
> points in the vector/sites file.
>
>>> My idea is to set a flag  (-a interpolate trough all the points) 
>>> that automatically select the old interpolation method to avoid any 
>>> segmentation fault.......
>>
>
> Please explain what you mean about the segmentation fault.
>
>>> so it should looks:
>>> -n means use old interpolation method
>>> -a means use old interpolation method over all the sites
>>
>
> Yes but this is actually what -n does.
>
>>> else use new method over points in region
>>>
>>> Impression and comments are welcome....
>>> Maxi
>>
>
> I'm not sure I understand what the improvement does. If you could 
> explain better what the problem is with the existing version, it might 
> help.
>
> Paul
>
>

-- 
_____________________________________________________

Ing. Massimiliano Cannata

SUPSI - Istituto Scienze della Terra
C.P. 72 - CH-6952 Canobbio (Ticino, Switzerland)
Tel +41 (0)91 935 12 25 - Fax +41 (0)91 935 12 09
mailto:massimiliano.cannata at supsi.ch
http://www.ist.supsi.ch

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