dash.closest.latlon

Returns the latitude-longitude points closest to a set of coordinates

Syntax



[coordinates] = dash.closest.latlon(coordinates, lats, lons)


[coordinates, latIndices, lonIndices] = dash.closest.latlon(…)

Description



[coordinates] = dash.closest.latlon(coordinates, lats, lons)

Searches through combinations of latitude and longitude points to find the values that are closest to specified latitude-longitude coordinates. This method is often used to locate the elements of a gridded dataset that are closest to a specific set of coordinates. Thus, the second and third inputs are usually the latitude and longitude metadata of a gridded dataset.

This function uses a haversine function to calculate the distance between sites. The haversine function is agnostic to longitude coordinate systems, so you may use longitudes on either -180:180 or 0:360, or even a mix of both coordinate systems.



[coordinates, latIndices, lonIndices] = dash.closest.latlon(…)

Also returns the indices of the closest latitude and closest longitude points within the examined sets of points. These outputs can be used to index into the closest elements of a gridded dataset.

Input Arguments

coordinates

numeric matrix [nCoordinates x 2]
A set of latitude-longitude coordinates in decimal degrees. The method will search for latitude-longitude combinations that are closest to these points. A numeric matrix with two columns. The first column holds the latitude points, and the second column is longitude.

lats

numeric vector [nLats]
The latitude points (decimal degrees) for the latitude-longitude combinations that will be tested. This is often the latitude metadata of a gridded dataset.

lons

numeric vector [nLons]
The longitude points (decimal degrees) for the latitude-longitude combinations that will be tested. This is often the longitude metadata of a gridded dataset.

Output Arguments

coordinates

numeric matrix [nCoordinates x 2]
The latitude-longitude combination closest to each of the input coordinates. First column is latitude, second column is longitude.

latIndices

vector, linear indices [nCoordinates]
The index of the latitude value in the closest point for each coordinate. These indices are relative to the “lats” input.

lonIndices

vector, linear indices [nCoordinates]
The index of the longitude value in the closest point for each coordinate. These indices are relative to the “lons” input.