GetDistance: Find distance between points on Earth

In EarthSystemDiagnostics/ecustools: A miscellaneous collection of R functions for working with time-series and paleo data.

Description

This is a general function to calculate the distance on Earth between a target location and all points in a field of coordinates. It provides a straighforward interface to the function distGeo from package geosphere.

Usage

GetDistance(lat0, lon0, lat, lon, get.nearest = FALSE, verbose = FALSE)

Arguments

lat0	numeric vector of length 1 with the latitude (in degree) of the target location relative to which distances are to be calculated.
lon0	numeric vector of length 1 with the longitude (in degree) of the target location.
lat	numeric vector of latitudes (in degree) of the positions for which distances from the target position are to be calculated.
lon	numeric vector of longitudes (in degree) of the positions for which distances from the target position are to be calculated. Must have the same length as lat.
get.nearest	logical; specify whether the given 'lat0' - 'lon0' pair shall be used _as is_ as the target location (FALSE), or instead the nearest point of the positions specified by 'lat' and 'lon' (TRUE). Selection of the nearest point is currently implemented with MinimizeSpherical, for which the "pfields" package needs to be installed.
verbose	logical; if TRUE an informative message regarding the selected target location is printed.

Details

This is a wrapper function whose purpose it is to provide a straighforward interface to the function distGeo; this includes:

• direct input of latitude/longitude values which are then shaped into the appropriate structure for distGeo;

• longitude values are automatically confined to [-180, 180] as needed by distGeo;

• if required, one can select the point closest to the target location as the reference for the distance calculations.

Value

Numeric vector of the same length as lat with the distances in km from the target location.

Author(s)

Thomas Münch

See Also

MinimizeSpherical; GetDistanceField; https://github.com/EarthSystemDiagnostics/pfields

Examples

# some coordinates
lat0 <- -75
lon0 <- 0
lat <- seq(-74, -80, -2)
lon <- seq(-2, 7, 3)

d <- GetDistance(lat0, lon0, lat, lon, verbose = TRUE)
range(d)

d <- GetDistance(lat0, lon0, lat, lon, get.nearest = TRUE, verbose = TRUE)
range(d)

EarthSystemDiagnostics/ecustools documentation built on Jan. 15, 2022, 5:22 p.m.