GRTS sampling - 2-level design
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 at 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
[[alternative HTML version deleted]]
_______________________________________________ R-sig-Geo mailing list R-sig-Geo at r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
-- Roger Bivand Emeritus Professor Department of Economics, Norwegian School of Economics, Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway. e-mail: Roger.Bivand at nhh.no https://orcid.org/0000-0003-2392-6140 https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en