Compares pairwise distances among sites with distances between the centers of the grid cells
the sites fall in, and prints a report. Connectivity models that work from cell to cell treat
each site as the center of its cell: the random walk functions (random_walk(),
pairwise_random_walk()), and the least-cost functions when sites are snapped to cell centers
(least_cost(), least_cost_paths(), and pairwise_least_cost(snap = TRUE)). For
these, sites separated by only a few cells have distorted distances and directions, and sites in
the same cell can't be distinguished at all. pairwise_least_cost() with its default
snap = FALSE places sites at their actual locations, so this check does not apply to it.
Value
Prints the number of site pairs, the number (and percentage) in the same grid cell,
and the distribution of discrepancies between cell and point distances, as percentages of
point distance. If return = TRUE, also returns a matrix of the ratios of cell distances to
point distances (NaN for a site with itself, and 0 for distinct sites in the same cell).
Details
Where many site pairs are affected, options are to use wind data on a finer grid, or to
downscale() the wind rose (see its documentation for how downscaling changes random walk
results).
Examples
rose <- windscape_example("wind_rose")
sites <- cbind(c(-110, -109.9, -100), c(35, 35.1, 40)) # the first two share a cell
check_cell_distance(rose, sites)
#> Total point pairs: 3
#> Point pairs in the same grid cell: 1 (33.3%)
#> Distribution of cell-point distance discrepancies:
#> 0--1%: 0 (0%)
#> 1--2.5%: 1 (33.3%)
#> 2.5--5%: 1 (33.3%)
#> 5--10%: 0 (0%)
#> 10--25%: 0 (0%)
#> 25--Inf%: 1 (33.3%)