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

[Francois Chartier]

i figired something out last night.  you can run an interpolation on
Selected Features only.  using the attribute table, i select some rows
based for example on elevation and i can run interpolation on these. this
would avoid creating different tables manually and running interpolation.
the next step would be to automate this process: for example if we want to
create multiple interpolations based on different selection. any idea how
to do this?

On Sun, Oct 28, 2018, 11:21 Nicolas Cadieux <nicolas.cadieux at archeotec.ca
wrote:

> 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
>> > _______________________________________________
>> > Qgis-user mailing list
>> > Qgis-user at lists.osgeo.org
>> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>> > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20181105/d23d0a59/attachment.html>