Returns the great circle distance between a location and all grid point in km

## Usage

```
dist_greatcircle(
lat1,
lon1,
lat2,
lon2,
r = earth_radius(),
method = c("haversine", "orthodrome", "vincenty", "euclidean")
)
```

## Arguments

- lat1, lon1
numeric vector. coordinate of point(s) 1 (degrees).

- lat2, lon2
numeric vector. coordinates of point(s) 2 (degrees).

- r
numeric. radius of the sphere (default = 6371.0087714 km, i.e. the radius of the Earth)

- method
Character. Formula for calculating great circle distance, one of:

`"haversine"`

great circle distance based on the haversine formula that is optimized for 64-bit floating-point numbers (the default)

`"orthodrome"`

great circle distance based on the spherical law of cosines

`"vincenty"`

distance based on the Vincenty formula for an ellipsoid with equal major and minor axes

- "euclidean"
Euclidean distance (not great circle distance!)

## Examples

```
dist_greatcircle(lat1 = 20, lon1 = 12, lat2 = c(50, 30), lon2 = c(40, 32))
#> [1] 4149.157 2296.583
dist_greatcircle(
lat1 = 20, lon1 = 12, lat2 = c(50, 30), lon2 = c(40, 32),
method = "orthodrome"
)
#> [1] 4149.157 2296.583
dist_greatcircle(
lat1 = 20, lon1 = 12, lat2 = c(50, 30), lon2 = c(40, 32),
method = "vincenty"
)
#> [1] 4149.157 2296.583
dist_greatcircle(
lat1 = 20, lon1 = 12, lat2 = c(50, 30), lon2 = c(40, 32),
method = "euclidean"
)
#> [1] 4076.220 2284.169
```