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Build a regular prediction grid over a region

Source: R/prediction-grid.R
make_prediction_grid.Rd

Creates a regular grid of centre points covering an sf region, at a given spatial resolution. Optionally filters the grid by depth using a user-supplied depth function. Coordinates are returned in the same units as the model (divided by coord_multiplier).

Usage

make_prediction_grid(
  region,
  resolution,
  crs = NULL,
  coord_multiplier = 1000,
  min_depth = NULL,
  max_depth = NULL,
  depth_fun = NULL,
  bathy_style = "raster_continuous"
)

Arguments

region

An sf polygon defining the prediction area (e.g. from make_survey_prediction_region()).

resolution

Numeric. Grid cell side length, in the model coordinate units (e.g. km). Internally multiplied by coord_multiplier to match the CRS units.

crs

Coordinate reference system. If NULL (default), taken from region.

coord_multiplier

Numeric factor to convert model units to CRS units. Default 1000.

min_depth, max_depth

Optional numeric depth limits. If either is supplied, grid cells with depth outside c(min_depth, max_depth) are dropped (min_depth defaults to 1, which removes land, and max_depth to Inf). Supplying either turns on depth extraction (see depth_fun/bathy_style).

depth_fun

Optional function taking an sf points object and returning a numeric vector of (positive) depths. Only used when min_depth or max_depth is set. If NULL (default), depth is extracted automatically via ggOceanMaps::get_depth() using bathy_style — supply your own depth_fun to use a different bathymetry source (e.g. a specific GEBCO file via bathy.style = "raster_user" and options(ggOceanMaps.userpath = ...), or a local raster/interpolation).

bathy_style

Character. bathy.style passed to ggOceanMaps::get_depth() when depth_fun is NULL. Default "raster_continuous" (ETOPO, bundled with ggOceanMaps — no extra download path needed). Ignored when depth_fun is supplied.

Value

A data frame (class sdmTMB_prediction_grid, so plot.sdmTMB_prediction_grid() can be used on it directly) with columns X, Y (in model units) and, when depth filtering is applied, a depth column. Carries crs, coord_multiplier and resolution attributes.

See also

make_survey_prediction_region(), plot.sdmTMB_prediction_grid()

Author

Mikko Vihtakari

Examples

# \donttest{
data(sebastes)
eggan <- subset(sebastes, cruiseseries == "EggaN")
region <- make_survey_prediction_region(eggan, crs = 32633, concavity = 5)

# max_depth turns on depth extraction, via ggOceanMaps::get_depth() by
# default (bathy_style controls the bathymetry source); cells outside
# c(1, max_depth) are dropped. plot() then colours by depth automatically.
# Here we pass the small bundled demonstration bathymetry as `depth_fun`
# to avoid the large bathymetry download get_depth() needs on first use.
grid <- make_prediction_grid(
  region, resolution = 20, max_depth = 1000, depth_fun = sebastes_depth
)
range(grid$depth)
#> [1]  10 970
plot(grid)


# A depth band, e.g. the depth range a slope survey targets
band <- make_prediction_grid(
  region, resolution = 20, min_depth = 400, max_depth = 1350,
  depth_fun = sebastes_depth
)
range(band$depth)
#> [1]  400 1340
# }