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.biv...@nhh.no
https://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
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