[GRASS-user] null values and v.surf.idw

[Luigi Ponti]

Javier Álvarez Rodríguez wrote:
>
> Dear people,
>
> I’m interpolating some data by means of v.surf.idw. I loaded data in a 
> database using v.in.ascii and create a vector layer. Here is an 
> example of five loaded fields of one row. X and y coordinates are in 
> the two first columns. Other fields are data to interpolate. But some 
> stations missed some data. So, the imported database contains blank 
> values whenever data is not available. This row has blank (no data or 
> null) values in data2:
>
> X;y;data1;data2;data3
>
> 623649;4784544;2.3;;1.98
>
> I have no problems using data1 and data3 in v.surf.idw procedure. The 
> problem appears when trying to use data2. It seems that the 
> interpolation procedure takes “0.0” value when it should not consider 
> anything. How can I manage null (no data) in v.surf.idw?
>
I had a similar problem recently and the mailing kindly suggested a 
solution that worked out. Please see:

http://article.gmane.org/gmane.comp.gis.grass.user/16380/

Hope it helps,
Luigi