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

[John Wilson]

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.

Would appreciate any thoughts...
John

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