[Qgis-user] qgis - run interpolation on table and selected attribute

[Nicolas Cadieux]

Salut,

If you don’t use a TIN, you can interpolate using, not the z value within a certain radius but rather, the number of points within a certain radius.  I know cloud Compare does that, saga and gdalgrid.  Look for the data metrics on this page.
https://www.gdal.org/gdal_grid.html#gdal_grid_metrics.  If the processing tools does not have that field, you will need to use Qgis 2x and modify the command line in the raster plugin or simply use gdal at the OSGeo4w command prompt.

Nicolas


> Le 28 oct. 2018 à 10:58, Francois Chartier <fra.chartier at gmail.com> a écrit :
> 
> thanks, for the interpolation, is there a way to increase the number of nodes. i tried inverse distance and nearest neighbour.  can we set it at for ex a node every 10 m?  
> i also created a voronoi mesh and based on delaunay triangle.  one the grid is built, can we interpolate the data on these nodes?   one application would be : a data set of concentrations at certain locations and we want to know what is the interpolated value at a given property line, road, structure etc?
> cheers
> f
> 
>> On Sat, Oct 27, 2018, 18:20 Nicolas Cadieux, <nicolas.cadieux at archeotec.ca> wrote:
>> Hi,
>> You can easily make a query then when you save the file, you can specify that you wish to save only the selected points.
>> 
>> You may have some difficulty with the interpolation.  I suggest you use gdalDem or Saga for this interpolation. Nearest neighbor will be the fastest interpolation method. If you can handle that may points or have thousands of files to deal with (LiDAR), contact me again.  Csv files, Python scripting and GDAL will be useful in those situations.  Cloud Compare will also excel at dealing with so many points.
>> 
>> Nicolas
>> 
>> > Le 27 oct. 2018 à 17:57, Francois Chartier <fra.chartier at gmail.com> a écrit :
>> > 
>> > Hi, 
>> > 
>> > I have a large data set 180k points consisting of XYZ and attribute, and i would like to interpolate the attribute at certain elevations only.
>> > i have created separate tables for the given elevations outside of qgis and then imported it and interpolate. 
>> > I think that one should be able to run a query and interpolate values based on the query result, or create a new data set, export query result into a new table in qgis, and then interpolate.  Is this possible?
>> > 
>> > Thanks, 
>> > F
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