diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..8227689
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 Trajectory, Ltd
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..9699273
--- /dev/null
+++ b/README.md
@@ -0,0 +1,27 @@
+# geodesy
+
+Go module geodesy provides the coordinate system conversion and the distance calculation.
+The default coordinate system is WGS84.
+This wraps [github.com/wroge/wgs84](github.com/wroge/wgs84) with object orientation,
+therefore you can change the coordinate system with its system.
+
+## Prerequisites
+
+- **[Go](https://go.dev)**: **1.20+**.
+
+## Installation
+
+Simply append the following import to your code, and then `go [build|run|test]`
+will automatically fetch the necessary dependencies:
+
+```go
+import "github.com/trajectoryjp/geodesy_go"
+```
+
+## Contribution
+
+You are very welcome to:
+
+- Create pull requests of any kind
+- Let me know if you are using this library and find it useful
+- Open issues with request for support because they will help you and many others
diff --git a/coordinates/Geocentric.go b/coordinates/Geocentric.go
new file mode 100644
index 0000000..1640a68
--- /dev/null
+++ b/coordinates/Geocentric.go
@@ -0,0 +1,36 @@
+package coordinates
+
+import (
+	"github.com/go-gl/mathgl/mgl64"
+	"github.com/wroge/wgs84"
+)
+
+// Geocentric is a type for geocentric coordinates.
+type Geocentric mgl64.Vec3
+
+// GeocentricReferenceSystem is the reference system for Geocentric.
+var GeocentricReferenceSystem = wgs84.GeocentricReferenceSystem{}
+
+// GeocentricFromGeodetic converts geodetic coordinates to geocentric coordinates.
+func GeocentricFromGeodetic(geodetic Geodetic) (geocentric Geocentric) {
+	geocentric[0], geocentric[1], geocentric[2] = GeodeticReferenceSystem.To(GeocentricReferenceSystem)(geodetic[0], geodetic[1], geodetic[2])
+	return
+}
+
+// X returns the x coordinate.
+// The unit is meter.
+func (geocentric *Geocentric) X() *float64 {
+	return &geocentric[0]
+}
+
+// Y returns the y coordinate.
+// The unit is meter.
+func (geocentric *Geocentric) Y() *float64 {
+	return &geocentric[1]
+}
+
+// Z returns the z coordinate.
+// The unit is meter.
+func (geocentric *Geocentric) Z() *float64 {
+	return &geocentric[2]
+}
diff --git a/coordinates/Geodetic.go b/coordinates/Geodetic.go
new file mode 100644
index 0000000..a5ecf20
--- /dev/null
+++ b/coordinates/Geodetic.go
@@ -0,0 +1,71 @@
+// Package coordinates contains types and functions of coordinates for geodesy.
+// The all types are based on [github.com/go-gl/mathgl/mgl64.Vec3], therefore you can convert each other.
+package coordinates
+
+import (
+	"math"
+
+	"github.com/go-gl/mathgl/mgl64"
+	"github.com/wroge/wgs84"
+)
+
+// Geodetic is a type for geodetic coordinates.
+type Geodetic mgl64.Vec3
+
+// GeodeticReferenceSystem is the reference system for Geodetic.
+// The default is WGS84.
+var GeodeticReferenceSystem = wgs84.LonLat()
+
+// GeodeticFromGeocentric converts geocentric coordinates to geodetic coordinates.
+func GeodeticFromGeocentric(geocentric Geocentric) (geodetic Geodetic) {
+	geodetic[0], geodetic[1], geodetic[2] = GeocentricReferenceSystem.To(GeodeticReferenceSystem)(geocentric[0], geocentric[1], geocentric[2])
+	return
+}
+
+// Longitude returns the longitude.
+// The unit is degree.
+func (geodetic *Geodetic) Longitude() *float64 {
+	return &geodetic[0]
+}
+
+// Latitude returns the latitude.
+// The unit is degree.
+func (geodetic *Geodetic) Latitude() *float64 {
+	return &geodetic[1]
+}
+
+// Altitude returns the altitude.
+// The unit is meter.
+func (geodetic *Geodetic) Altitude() *float64 {
+	return &geodetic[2]
+}
+
+// GenerateLocalFromGeocentric generates a function to convert geocentric coordinates to local coordinates.
+func (origin Geodetic) GenerateLocalFromGeocentric() func(geocentric Geocentric) mgl64.Vec3 {
+	vector := mgl64.Vec3(GeocentricFromGeodetic(origin))
+	γᵣ := vector.Len()
+	ψ := math.Asin(vector.Z() / γᵣ)
+	λ := origin[0] * math.Pi / 180.0
+	rotator := mgl64.Rotate3DZ(-math.Pi / 2.0).Mul3(mgl64.Rotate3DY(ψ - math.Pi/2.0)).Mul3(mgl64.Rotate3DZ(-λ))
+
+	return func(geocentric Geocentric) mgl64.Vec3 {
+		local := rotator.Mul3x1(mgl64.Vec3(geocentric))
+		local[2] -= γᵣ
+		return local
+	}
+}
+
+// GenerateGeocentricFromLocal generates a function to convert local coordinates to geocentric coordinates.
+func (origin Geodetic) GenerateGeocentricFromLocal() func(local mgl64.Vec3) Geocentric {
+	vector := mgl64.Vec3(GeocentricFromGeodetic(origin))
+	γᵣ := vector.Len()
+	ψ := math.Asin(vector.Z() / γᵣ)
+	λ := origin[0] * math.Pi / 180.0
+	rotator := mgl64.Rotate3DZ(λ).Mul3(mgl64.Rotate3DY(math.Pi/2.0 - ψ)).Mul3(mgl64.Rotate3DZ(math.Pi / 2.0))
+
+	return func(local mgl64.Vec3) Geocentric {
+		local[2] += γᵣ
+		geocentric := Geocentric(rotator.Mul3x1(mgl64.Vec3(local)))
+		return geocentric
+	}
+}
diff --git a/coordinates/Spherical.go b/coordinates/Spherical.go
new file mode 100644
index 0000000..2fb4334
--- /dev/null
+++ b/coordinates/Spherical.go
@@ -0,0 +1,98 @@
+package coordinates
+
+import (
+	"math"
+
+	"github.com/go-gl/mathgl/mgl64"
+)
+
+// Spherical is a type for spherical coordinates.
+// This is for calculating [Great-circle navigation].
+//
+// [Great-circle navigation]: https://en.wikipedia.org/wiki/Great-circle_navigation
+type Spherical mgl64.Vec3
+
+// Longitude returns the longitude.
+// The unit is degree.
+func (spherical *Spherical) Longitude() *float64 {
+	return &spherical[0]
+}
+
+// Latitude returns the latitude.
+// The unit is degree.
+func (spherical *Spherical) Latitude() *float64 {
+	return &spherical[1]
+}
+
+// Altitude returns the altitude.
+// The unit is meter.
+func (spherical *Spherical) Altitude() *float64 {
+	return &spherical[2]
+}
+
+// GetLengthTo returns the length to the arrival.
+// The unit is meter.
+func (departure Spherical) GetLengthTo(arrival Spherical) float64 {
+	greatCircleDistance := departure.GetGreatCircleDistanceTo(arrival)
+	altitudeDifference := *arrival.Altitude() - *departure.Altitude()
+	return math.Sqrt(greatCircleDistance*greatCircleDistance + altitudeDifference*altitudeDifference)
+}
+
+// GetGreatCircleDistanceTo returns the great circle distance to the arrival.
+// The unit is meter.
+func (departure Spherical) GetGreatCircleDistanceTo(arrival Spherical) float64 {
+	φDeparture := *departure.Latitude() * math.Pi / 180.0
+	φArrival := *arrival.Latitude() * math.Pi / 180.0
+	λDeparture := *departure.Longitude() * math.Pi / 180.0
+	λArrival := *arrival.Longitude() * math.Pi / 180.0
+	λDefference := λArrival - λDeparture
+
+	sinφDeparture := math.Sin(φDeparture)
+	sinφArrival := math.Sin(φArrival)
+	cosφDeparture := math.Cos(φDeparture)
+	cosφArrival := math.Cos(φArrival)
+	sinλDefference := math.Sin(λDefference)
+	cosλDefference := math.Cos(λDefference)
+
+	b := cosφDeparture*sinφArrival - sinφDeparture*cosφArrival*cosλDefference
+	c := cosφArrival * sinλDefference
+	d := sinφDeparture*sinφArrival + cosφDeparture*cosφArrival*cosλDefference
+	tanσDifference := math.Sqrt(b*b + c*c) / d
+	σDifference := math.Atan(tanσDifference)
+	return GeodeticReferenceSystem.Datum.A() * σDifference
+}
+
+// GetDirectionTo returns the direction to the arrival.
+// The unit is degree.
+func (departure Spherical) GetDirectionTo(arrival Spherical) float64 {
+	φDeparture := *departure.Latitude() * math.Pi / 180.0
+	φArrival := *arrival.Latitude() * math.Pi / 180.0
+	λDeparture := *departure.Longitude() * math.Pi / 180.0
+	λArrival := *arrival.Longitude() * math.Pi / 180.0
+	λDefference := λArrival - λDeparture
+
+	sinφDeparture := math.Sin(φDeparture)
+	sinφArrival := math.Sin(φArrival)
+	cosφDeparture := math.Cos(φDeparture)
+	cosφArrival := math.Cos(φArrival)
+	sinλDefference := math.Sin(λDefference)
+	cosλDefference := math.Cos(λDefference)
+
+	tanα := cosφArrival*sinλDefference / (cosφDeparture*sinφArrival - sinφDeparture*cosφArrival*cosλDefference)
+	return math.Atan(tanα) * 180.0 / math.Pi
+}
+
+// GetDirectionOnEquator returns the direction on the equator.
+// The unit is degree.
+func (spherical Spherical) GetDirectionOnEquator(direction float64) float64 {
+	α := direction * math.Pi / 180.0
+	φ := *spherical.Latitude() * math.Pi / 180.0
+
+	sinα := math.Sin(α)
+	cosα := math.Cos(α)
+	sinφ := math.Sin(φ)
+	cosφ := math.Cos(φ)
+
+	tanα0 := sinα*cosφ / math.Sqrt(cosα*cosα+sinα*sinα*sinφ*sinφ)
+	return math.Atan(tanα0) * 180.0 / math.Pi
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..bc7614e
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,10 @@
+module github.com/trajectoryjp/geodesy_go
+
+go 1.20
+
+require (
+	github.com/go-gl/mathgl v1.1.0
+	github.com/wroge/wgs84 v1.1.7
+)
+
+require golang.org/x/image v0.0.0-20190321063152-3fc05d484e9f // indirect
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..3b629d1
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,7 @@
+github.com/go-gl/mathgl v1.1.0 h1:0lzZ+rntPX3/oGrDzYGdowSLC2ky8Osirvf5uAwfIEA=
+github.com/go-gl/mathgl v1.1.0/go.mod h1:yhpkQzEiH9yPyxDUGzkmgScbaBVlhC06qodikEM0ZwQ=
+github.com/wroge/wgs84 v1.1.7 h1:8WVUUrpjysYxrn0ssWX7z90SOUKCuHt9NQ5tg9ovjIY=
+github.com/wroge/wgs84 v1.1.7/go.mod h1:mc1F8ubW03DO4zaf/006cmhaiMlfvbKmqVAcPuAtsNA=
+golang.org/x/image v0.0.0-20190321063152-3fc05d484e9f h1:FO4MZ3N56GnxbqxGKqh+YTzUWQ2sDwtFQEZgLOxh9Jc=
+golang.org/x/image v0.0.0-20190321063152-3fc05d484e9f/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
diff --git a/workflows/main.yml b/workflows/main.yml
new file mode 100644
index 0000000..f4e24c2
--- /dev/null
+++ b/workflows/main.yml
@@ -0,0 +1,21 @@
+name: Go package
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: '1.18'
+
+      - name: Build
+        run: go build -v ./...
+
+      - name: Test
+        run: go test -v ./...