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

[Roger Bivand]

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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-- 
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