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geodesic

geodesic is a Go package providing operations for performing accurate measurements of Earth. Includes a Go port of the geodesic routines from GeographicLib along with general-purpose spherical algorithms.

Features

• Precise distance calculations (5-15 nanometer)
• Calculate the area and perimeter of a polygon
• Get the length of a polyline
• Direct and Inverse solutions
• Optional spherical formulas for efficency, such as Haversine.

Installing

To start using geodesic, install Go and run go get:

$ go get -u github.com/tidwall/geodesic

This will retrieve the library.

Using

All operations are performed on an Ellipsoid object.

To create a custom ellipsoid:

• geodesic.NewEllipsoid: For highly accurate geodesic routines.
• geodesic.NewSpherical: For faster spherical routines such as Haversine.

// The first argument is the radius and the second is the flattening.
myEllipsoid := geodesic.NewEllipsoid(6378137.0, 1.0/298.257223563)

Or, you can simply use the built-in geodesic.WGS84 non-spherical ellipsoid, which conforms to the WGS84 standard.

// The argument is the radius.
mySphere := geodesic.NewSpherical(6378137.0)

Or, you can use the geodesic.Globe spherical ellipsoid, which represents Earth as a terrestrial globe.

Examples

Calculate distance between two points.

var dist float64
geodesic.WGS84.Inverse(33.4911, -112.4223, 32.1189, -113.1123, &dist, nil, nil)
fmt.Printf("%f meters\n", dist)
// output: 
// 165330.214571 meters

Calculate initial azimuth from point A to point B.

var azi float64
geodesic.WGS84.Inverse(33.4911, -112.4223, 32.1189, -113.1123, nil, &azi, nil)
fmt.Printf("%f degrees\n", azi)
// output:
// -156.803310 degrees

Calculate final azimuth from point A to point B.

var azi float64
geodesic.WGS84.Inverse(33.4911, -112.4223, 32.1189, -113.1123, nil, nil, &azi)
fmt.Printf("%f degrees\n", azi)
// output:
// -157.177169 degrees

Calculate distance and azimuths at the same time.

var dist, azi1, azi2 float64
geodesic.WGS84.Inverse(33.4911, -112.4223, 32.1189, -113.1123, &dist, &azi1, &azi2)
fmt.Printf("%f meters, %f degrees, %f degrees\n", dist,azi1,azi2)
// output:
// 165330.214571 meters, -156.803310 degrees, -157.177169 degrees

Calculate destination using an initial point, azimuth, and distance.

var lat, lon float64
geodesic.WGS84.Direct(33.4911, -112.4223, -156.803310, 165330.214571, &lat, &lon, nil)
fmt.Printf("%f, %f\n", lat, lon)
// output: 
// 32.118900, -113.112300

Calculate the area and perimeter of a polygon.

// Arizona
poly := WGS84.PolygonInit(false)
poly.AddPoint(36.99377, -109.050292)
poly.AddPoint(36.96744, -114.049072)
poly.AddPoint(36.26199, -114.016113)
poly.AddPoint(36.08462, -114.279785)
poly.AddPoint(36.11125, -114.730224)
poly.AddPoint(34.86790, -114.631347)
poly.AddPoint(34.47939, -114.367675)
poly.AddPoint(34.29806, -114.104003)
poly.AddPoint(33.89777, -114.532470)
poly.AddPoint(33.58716, -114.543457)
poly.AddPoint(33.35806, -114.708251)
poly.AddPoint(33.09154, -114.708251)
poly.AddPoint(32.87036, -114.444580)
poly.AddPoint(32.74108, -114.719238)
poly.AddPoint(32.50049, -114.818115)
poly.AddPoint(31.33487, -111.093749)
poly.AddPoint(31.35363, -109.050292)
poly.AddPoint(36.99377, -109.050292)
var area, perimeter float64
poly.Compute(false, false, &area, &perimeter)
fmt.Printf("%f area (km²), %f perimeter (meters)\n", area/1000000, perimeter)
// output:
// 294838.722804 area (km²), 2254910.021767 perimeter (meters)

For full api documentation see https://pkg.go.dev/github.com/tidwall/geodesic#pkg-index.