[Qgis-user] sampling points from multipe rasters

[Matt Boyd]

Hi Tyler,
the point sampling tool plugin will allow you to select multiple rasters to
sample from and output to the same file. It also allows you to save the
results in a number of different formats (geopackage, csv and shapefile).
If you've got access to python in your version of R then geopandas can read
geopackage files directly, I find that a lot more useful than csv.

I use this workflow. The slowest part is the point sampling depending on
the number and size of rasters and points.

Matt



On Tue, May 5, 2020 at 6:49 AM Tyler Smith <tyler at plantarum.ca> wrote:

> Hi,
>
> I have 30 raster layers, and I need to sample 10,000 random points
> from each layer (using the same set of points each time). I think
> my options are:
>
> 1. Create a virtual raster, and sample. This has the downside that
> the identify of the 30 layers will be replaced by generic 'band1',
> 'band2' labels.
>
> 2. Sample the layers directly, using a batch process. This has the
> downside that it appears to output to gpkg format, and creates 30
> separate files. I will need to open each of these files, export
> the points they contain to csv, and then combine the into a single
> table in R for analysis.
>
> Is there a way to create a virtual raster that retains the layer
> names in the stack? Alternatively, can I bulk sample multiple
> rasters and have the output combined in a single table?
>
> Thanks,
>
> Tyler
>
> --
> Tyler Smith
> plantarum.ca
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