Calculate (signed) distances between coordinates

Usage

find_dists(locations, longlat = TRUE, origin = 1L, return_grid = FALSE, ...)

Arguments

locations: A matrix or data.frame of 2D points, the first column is x/longitude, and the second column is y/latitude.
longlat: Logical, if TURE Great Circle (WGS84 ellipsoid) distance; if FALSE, Euclidean distance.
origin: Optional; used when longlat is TRUE. An integer index indicating the reference location which will be used as the origin.
return_grid: Logical; used when longlat is TRUE. If TRUE the mapped coordinates on a 2D plane is returned.
...: Optional arguments passed to .find_dists().

Value

A list of distance matrices. If return_grid is TRUE, a list consists of a list of distance matrices, the mapped 2D grid, and the origin is returned.

Details

locations must be a matrix or data.frame containing 2 columns, first column x/longitude, and second column y/latitude. The row names of locations are used as the names of the locations.

If longlat is TRUE, the original coordinates are mapped to a 2D Euclidean plane given the reference location. First, the Great Circle (WGS84 ellipsoid) signed distance matrices are calculated, where the original latitudes are replaced by the the mean of them to find the signed longitudinal distances and the original longitudes are replaced by the the mean of them to find the signed latitudinal distances. Then given the index of a reference location origin, a new set of coordinates in a 2D plane is generated where the coordinates are determined by the signed distances between the locations and the reference location. Finally distance matrices of the new coordinates are outputted.

Examples

lon <- c(110, 120, 130)
lat <- c(50, 55, 60)
locations <- cbind(lon, lat)
rownames(locations) <- paste("Site", 1:3)
find_dists(locations)
#> $h
#>           Site 1   Site 2   Site 3
#> Site 1    0.0000 847.5798 1692.986
#> Site 2  847.5798   0.0000  845.408
#> Site 3 1692.9859 845.4080    0.000
#> 
#> $h1
#>           Site 1    Site 2     Site 3
#> Site 1    0.0000 -639.3934 -1275.5045
#> Site 2  639.3934    0.0000  -636.1111
#> Site 3 1275.5045  636.1111     0.0000
#> 
#> $h2
#>          Site 1    Site 2     Site 3
#> Site 1    0.000 -556.3880 -1113.2338
#> Site 2  556.388    0.0000  -556.8459
#> Site 3 1113.234  556.8459     0.0000
#>