[gdal-dev] gdal_grid: number of data points to use

Jan Hartmann j.l.h.hartmann at uva.nl
Sat Jan 18 07:47:23 PST 2014

Thanks Even. How difficult would it be to let gdal_gid use the nearest 
points? The way it works now does not make much sense for mapping. 
Another very usable solution would be to select the nearest points in 
each quadrant relative to the interpolation point (NE, SE, SW, SE). It 
is available in dedicated interpolation programs like Surfer, and I 
always found it very useful. Funding would be possible.


On 01/18/2014 01:50 PM, Even Rouault wrote:
> Le samedi 18 janvier 2014 12:48:23, Jan Hartmann a écrit :
>> gdal_grid has the option to set a minimum and maximum number of data
>> points to use for interpolation. How are these data points selected from
>> the total number of points? Are they always the nearest points to the
>> grid-point that is interpolated?
> Jan,
> if less than min_points match the selection of the algorithm, the nodata value
> will be returned
> and when iterating over source points (in the order they are present in the
> source OGR layer), the algorithm will stop as soon as max_points is reached.
> The selected points are consequently not necessarily the nearest points, but
> they will be contained in the search ellipse (since max_points is only taken
> into account if you define radius1 and radius2)
> Even

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