The grid cell a position falls in — cc_grid

The one rule that keys a position to a cell of the CalCOFI grid: the cell whose polygon intersects the point, tested on longitude/latitude as planar coordinates (no great-circle edges), and, for a point on an edge shared by two or more cells, the cell whose key sorts first in byte order. calcofi4db::assign_grid_key() applies the same rule in DuckDB (min(grid_key) ... WHERE ST_Intersects(point, geom)), so R and the database agree on every position, including one on an edge.

Usage

cc_grid_key(lon, lat, grid = calcofi4r::cc_grid, key = "grid_key")

Arguments

lon, lat: longitude and latitude in decimal degrees (WGS 84); a missing or non-finite coordinate returns NA
grid: an sf of cells in EPSG:4326 with a key column; default the bundled cc_grid
key: name of the key column in grid (default "grid_key")

Value

character vector of keys, NA where the position is in no cell (on land, or outside the grid)

Examples

# official station 90.0 37.0, and a point in Los Angeles (on land: NA)
cc_grid_key(lon = c(-118.38708, -118.25), lat = c(33.18462, 34.05))
#> [1] "st37-ln90" NA         
# the same station in the previous grid: another cell, under a name the new grid also uses
cc_grid_key(-118.38708, 33.18462, grid = cc_grid_v1)
#> [1] "st35-ln90"