find_leg {himach}

Find best non-stop route between 2 airports

Description

find_leg finds the quickest non-stop route for ac between two airports ap2.

Usage

find_leg(
  ac,
  ap2,
  route_grid,
  fat_map,
  ap_loc,
  avoid = NA,
  enforce_range = TRUE,
  best_by_time = TRUE,
  grace_km = NA,
  shortcuts = TRUE,
  ad_dist_m = 100 * 1000,
  ad_nearest = 12,
  max_leg_circuity = 1.4,
  ...
)

Arguments

ac, ap2, route_grid, fat_map, ap_loc, avoid

See find_route

enforce_range

If TRUE (default) then leg is constrained to aircraft range, otherwise routes of excess range can be found.

best_by_time

If TRUE (default) then the quickest route is found, else the shortest distance.

grace_km

Default NA. Otherwise, if great circle distance is within 3pct of aircraft range, then add grace_kmkm to the range.

shortcuts

If TRUE (default) then path will be checked for great circle shortcuts.

ad_dist_m

The length of arrival/departure links, in m. (Default 100,000=100km)

ad_nearest

The number of arrival/departure links to create (Default 12)

max_leg_circuity

The maximum detour over great circle distance that can be flown to find a quick over-sea route. Default 1.4.

...

Other parameters, passed to make_route_envelope

Details

This function finds the quickest non-stop route between two airports. A 'route' is made up of one or two 'legs' (airport to airport without intermediate stop). find_route makes one or more calls to find_leg as required.

It assumes that the routing grid, route_grid, has already been classified as land or sea using the map fat_map. The map is further used when converting the grid-based route to one of great-circle segments.

In fact find_leg finds up to 4 versions of the path:

1. A great circle, direct between the airports

2. A grid path, consisting of segments of the routing grid, plus departure and arrival routes from the airports

3. A simplification of the grid path to great circle segments

4. shortcuts defaults to TRUE. Without this, you see near-raw Dijkstra results, which are _not_ shortest great circle.

Legs are automatically saved in route_cache and retrieved from here if available rather than re-calculated. See vignette on caching for cache management.

Value

Dataframe with details of the leg

Examples

# need to load some of the built-in data (not run)
## Not run: 
aircraft <- make_aircraft(warn = FALSE)
airports <- make_airports(crs = crs_Pacific)
# get test datasets
NZ_buffer30 <- hm_get_test("buffer")
NZ_grid <- hm_get_test("grid")

options("quiet" = 4) #for heavy reporting
# from Auckland to Christchurch
ap2 <- make_AP2("NZAA","NZCH",airports)
routes <- find_leg(aircraft[4,],
                    ap2,
                    fat_map = NZ_buffer30,
                    route_grid = NZ_grid,
                    ap_loc = airports)

## End(Not run)