Coord

This modules aims to be a port of portions of the library Geodesy.

Right now it provides structs to represent locations with points in UTM and LatLng format, and functions to convert between the two formats.

The module has been tested by comparing the results of converting hundreds of thousands of points against the reference implementation GeoConvert. The conversion functions in GeoConvert were initially written by the author of the paper which introduced the algorithms used by this module and Geodesy to convert points between latitude/longitude and UTM. Many thanks to the authors of PropCheck and PropEr for making this automated testing feasible.

Converting from latitude and longitude to UTM

iex> use Coord
iex> LatLng.new(51.178861, -1.826412) |> UTM.from()
%Coord.Point.UTM{
  datum: %Coord.Datum{
    ellipsoid: %Coord.Datum.Ellipsoid{
      a: 6378137,
      b: 6356752.314245,
      f: 0.0033528106647474805
    }
  },
  e: 582031.9577723305,
  hemi: :n,
  n: 5670369.804561083,
  zone: 30
}

Converting from UTM to latitude and longitude

iex> use Coord
iex> UTM.new(30, :n, 582031.96, 5670369.80) |> LatLng.from()
%Coord.Point.LatLng{
  lat: 51.17886095867467,
  lng: -1.8264119691783214
}

Datum

The default datum is WGS84, but you can specify a different datum if it can be represented by a surface defined using the same parameters as WGS84. See Coord.Datum and Coord.Datum.Ellipsoid.

Documentation

Published to https://hexdocs.pm/coord

Testing

The LatLng -> UTM and UTM -> LatLng conversions in this library are tested against the reference implementation GeographicLib, which Geodesy is also based on. This means that to run some of the tests you will need to install the command line utility GeoConvert. On Ubuntu you may be able to do this via apt install geographiclib-tools.

Installation

The package can be installed by adding coord to your list of dependencies in mix.exs:

def deps do
  [
    {:coord, "~> 0.1.0"}
  ]
end