[Qgis-user] Working with irregular magnetometry data points - converting them to an image

[C Hamilton]

Thanks Ben,

I will give that a try. I am finding that the Interpolation algorithm is
taking forever on a small data set.

Doesn't the Postgres PDAL extension handle point data like this? Would
there be a benefit of putting the data in PostGIS?

Thanks,

Calvin

On Fri, Apr 20, 2018 at 1:10 PM, Benjamin Ducke <benducke at fastmail.fm>
wrote:

> Hi Calvin,
>
> On 20/04/18 18:46, Richard McDonnell wrote:
> > Calvin,
> >
> > Under Processing Toolbox, Type interpolation into the search bar, the
> > tool you want can be found there.
>
> None of the typical GIS interpolation tools will be
> of much help here, since they have all been optimized
> to work with relatively sparse data. They will be
> too inefficient for high-resolution geomagnetic data.
>
> You data is already dense, with some gaps. So you need
> something that is fast and efficient for small
> interpolation radii, and will not produce too many
> artefacts.
>
> If you can use the GRASS7 plug-in from within QGIS,
> than this is a good processing path:
>
> 1. Rasterize your data points, using a cell size
> small enough so that you don't have too much information
> loss (i.e. not too many occurrences of more than one data
> point per cell). This might take a little trial and error
> to find good settings. You should end up with a raster
> where you have gaps of max. 1-3 empty cells between cells
> with measurement data.
>
> Now you need to fill these relatively small gaps.
>
> 2. Use r.fill.stats from current GRASS 7.4:
>
> https://grass.osgeo.org/grass74/manuals/r.fill.stats.html
>
> ... because that has been designed exactly for the
> purpose. Set the interpolation radius as small as
> possible, so that it just manages to fill the gaps.
> With a small radius, r.fill.stats is very fast and
> memory efficient, even on very large raster datasets.
>
> Note that r.fill.stats is part of GRASS 7 only since
> version 7.4. If your QGIS ships with an earlier
> version, then you might have to update your GRASS 7
> binaries manually.
>
> Best,
>
> Ben
>
> > Regards,
> >
> > Richard.
> >
> > On 20/04/2018 16:42, C Hamilton wrote:
> >> I don't know how many of you have worked with archaeological
> >> magnetormetry data, but I have been asked to help with magnetometry
> >> data of the ancient Mound Builders in North America. I am looking for
> >> some suggestion on how to best turn the irregular magnetic data points
> >> into an image.
> >>
> >> I see an Interpolation plugin that perhaps is the solution, but I also
> >> see that it is not part of QGIS 3. Is this because it has not been
> >> ported yet, or is not going to be porter, or is there a better solution?
> >>
> >> I don't know if any of the Lidar tools would work for this or not.
> >> LASTools is a commercial product and the locked version only works
> >> with small data sets and adds noise unless you purchase a license. At
> >> least that is how it was the last time I used it.
> >>
> >> Thanks for any suggestions.
> >>
> >> Calvin
> >>
> >>
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> > --
> > *_Richard McDonnell_*
> > *GIS Specialist PgD GIS AssocSCSI*
> > *OPW FRM Data Management*
> > *52 Stephens Green, Dublin 2.*
> > TEL: 01 6476543
> >
> > <http://www.opw.ie/>
> >
> >
> >
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> >
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>
>
> --
> Dr. Benjamin Ducke
> Deutsches Archäologisches Institut (DAI)
> Zentrale Berlin, IT-Referat
> * Projekt "Stunde Null" *
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