make_route_grid creates, and optionally classifies, a lat-long route grid
Usage
make_route_grid(
fat_map,
name,
target_km = 800,
lat_min = -60,
lat_max = 86,
long_min = -180,
long_max = 179.95,
classify = FALSE
)Arguments
- fat_map
MULTIPOLYGON map defining land regions
- name
String assigned to the name slot of the result
- target_km
Target length. Default 800km only to avoid accidentally starting heavy compute. 30-50km would be more useful.
- lat_min, lat_max
Latitude extent of grid
- long_min, long_max
Longitude extend of grid. Two allow small grids crossing the 180 boundary, the function accepts values outside [-180,180), then rounds to within this range.
- classify
Whether to classify each link. Defaults to FALSE only to avoid accidentally starting heavy compute.
Details
This function creates a GridLat object that contains a set of point on a lat long grid (ie all the points are on lines of latitude). It also joins these points into a lattice. Optionally, but required later, it classifies each link as land, sea, or transition, with reference to a given map (typically including a coastal buffer).
The definitions are
land: both ends of the link are on land
sea: both ends are on sea, and the link does not intersect the land
transition: otherwise
The length of the links will be around target_km or 50pct longer
for the diagonal links.
For more details see the help vignette:
vignette("Supersonic Routing", package = "himach")
Examples
NZ_buffer <- hm_get_test("buffer")
system.time(
p_grid <- make_route_grid(NZ_buffer,"NZ lat-long at 300km",
target_km = 300, classify = TRUE,
lat_min = -49, lat_max = -32,
long_min = 162, long_max = 182)
)
#> Made the grid:0
#> Making the basic lattice:
#>
#> Adding geo & distance to the lattice...
#>
#> Added geo & distance to the lattice:0.7
#> Classifying points in the lattice as land.
#> Classified as land:0.7
#> Classifying lines in the lattice as land.
#> Classified as land:0.7
#> Calculated all phases:0.7
#> Converting points and lattice to data table.
#> user system elapsed
#> 0.758 0.000 0.758