[R-sig-Geo] GRTS sampling - 2-level design

[John Wilson]

Oh, sorry - I normally use the grts() function from the spsurvey package.
My hacky approach was to make 10 balanced points with grts(), followed by
imposing a 5 km buffer around each one, and either systematic sampling
within the buffer circle, or running a separate GRTS for the 5 points
within each 5 km buffer circle. Even writing this makes me cringe though,
so hoping for something legitimate... I'll contact the authors if I don't
get any solid leads on here.

On Thu, Oct 7, 2021 at 10:40 AM Roger Bivand <Roger.Bivand using nhh.no> wrote:

> On Thu, 7 Oct 2021, John Wilson wrote:
>
> > Hi everyone,
> >
> > I'm working on a sampling design using GRTS, but I'm running into a
> > logistics problem. The field crew can set 5 nets per day, but only
> within a
> > 5 km stretch, due to travel time constraints. With 10 sampling days,
> that's
> > a total of 50 sites. The overall sampling area is huge, so running a
> > regular GRTS design for 50 sites results, of course, in much larger
> > distances between sampling points.
> >
> > Is there a legitimate way to create a 2-level GRTS design, where in step
> 1
> > we choose 10 spatially-balanced sampling points (one "core" point per
> > sampling day), and then for each of these "core points", we create a grid
> > of 5 sampling points that are constrained to all be within 5 km from each
> > other? I can make that happen code-wise, but am not sure what the
> > implications on spatial balance are, or if there's a built-in way to do
> > this.
>
> Do you have a code example? Are you using BalancedSampling, SDraw or
> Spbsampling or packages (probably SDraw)? Have you run any simulations to
> try to get a first assessment on the impact of constraining your sample?
> Might approach a package author also help?
>
> Roger
>
>
> >
> > Would appreciate any thoughts...
> > John
> >
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> >
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>
> --
> Roger Bivand
> Emeritus Professor
> Department of Economics, Norwegian School of Economics,
> Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway.
> e-mail: Roger.Bivand using nhh.no
> https://orcid.org/0000-0003-2392-6140
> https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
>

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