MazamaLocationUtils (version 0.4.3)

table_getNearestDistance: Return distances to nearest known locations

Description

Returns distances between target locations and the closest location found in locationTbl (if any). Target locations are specified with longitude and latitude.

For each target location, only a single distance to the closest known location is returned. If no known location is found within distanceThreshold, the distance associated with that target location will be NA. The length and order of resulting distances will match the order of the incoming target locations.

Usage

table_getNearestDistance(
  locationTbl = NULL,
  longitude = NULL,
  latitude = NULL,
  distanceThreshold = NULL,
  measure = c("geodesic", "haversine", "vincenty", "cheap")
)

Value

Vector of closest distances between target locations and known locations.

Arguments

locationTbl

Tibble of known locations.

longitude

Vector of target longitudes in decimal degrees E.

latitude

Vector of target latitudes in decimal degrees N.

distanceThreshold

Distance in meters.

measure

One of "geodesic", "haversine", "vincenty" or "cheap" specifying desired method of geodesic distance calculation.

Use Case

You may have a set of locations of interest for which you want to assess whether any monitoring locations are nearby. In this case, the locations of interest will provide longitude and latitude while locationTbl will be the known location table associated with the monitoring locations.

The resulting vector of distances will tell you the distance, for each target location, to the nearst monitoring location.

Examples

library(MazamaLocationUtils)

locationTbl <- get(data("wa_monitors_500"))

# Wenatchee
lon <- -120.325278
lat <- 47.423333

# Too small a distanceThreshold will not find a match
table_getNearestDistance(locationTbl, lon, lat, distanceThreshold = 50)

# Expanding the distanceThreshold will find one
table_getNearestDistance(locationTbl, lon, lat, distanceThreshold = 5000)