go-proj

Package go-proj provides an interface to PROJ.

Features

• High performance bulk transformation of coordinates.
• Idiomatic Go API, including complete error handling.
• Supports PROJ versions 6 and upwards.
• Compatible with all geometry libraries.
• Convenience functions for handling coordinates as []float64s.
• Automatically handles C memory management.
• Well tested.

Install

$ go get github.com/twpayne/go-proj/v10

You must also install the PROJ development headers and libraries. These are typically in the package libproj-dev on Debian-like systems, proj-devel on RedHat-like systems, and proj in Homebrew.

Example

func ExamplePJ_Forward() {
	pj, err := proj.NewCRSToCRS("EPSG:4326", "EPSG:3857", nil)
	if err != nil {
		panic(err)
	}

	// Start with Zürich's WGS84 latitude/longitude.
	zurich4326 := proj.NewCoord(47.374444, 8.541111, 408, 0)
	fmt.Printf("initial: x=%.6f y=%.6f z=%.6f\n", zurich4326.X(), zurich4326.Y(), zurich4326.Z())

	// Convert Zürich's WGS84 latitude/longitude to Web Mercator.
	zurich3857, err := pj.Forward(zurich4326)
	if err != nil {
		panic(err)
	}
	fmt.Printf("forward: x=%.6f y=%.6f z=%.6f\n", zurich3857.X(), zurich3857.Y(), zurich3857.Z())

	// ...and convert back.
	zurich4326After, err := pj.Inverse(zurich3857)
	if err != nil {
		panic(err)
	}
	fmt.Printf("inverse: x=%.6f y=%.6f z=%.6f", zurich4326After.X(), zurich4326After.Y(), zurich4326After.Z())

	// Output:
	// initial: x=47.374444 y=8.541111 z=408.000000
	// forward: x=950792.127329 y=6003408.475803 z=408.000000
	// inverse: x=47.374444 y=8.541111 z=408.000000
}

Comparisons with other PROJ bindings

There are many existing bindings for PROJ. Generally speaking, these:

• Only transform one coordinate a time, making them extremely slow when transforming large number of coordinates.

• Are tied to a single geometry representation.

• Do not handle errors during transformation.

• Are no longer maintained.

These existing bindings include:

• github.com/everystreet/go-proj, latest commit December 11, 2021.

• github.com/go-spatial/proj is an incomplete rewrite of PROJ4 in Go with the last commit on October 25, 2019.

• github.com/omniscale/go-proj has limited functionality.

• github.com/pebbe/go-proj-4 has limited functionality with the last commit on February 20, 2021.

• github.com/xeonx/proj4 has limited functionality with a last commit on December 23, 2015.

License

MIT