init

Author: rot1024

.github/workflows/ci.yml

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+name: CI
+on:
+  workflow_call:
+  push:
+    branches:
+      - main
+  pull_request:
+jobs:
+  ci:
+    name: CI
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+      - uses: golangci/golangci-lint-action@v6
+        with:
+          version: v1.64
+          skip-cache: true
+      - name: test
+        run: go test ./... -v -race -coverprofile=coverage.txt -covermode=atomic
+      - name: Send coverage report
+        uses: codecov/codecov-action@v4
+        with:
+          file: coverage.txt

.gitignore

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+*.asc

LICENSE

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+MIT License
+
+Copyright (c) 2025 Eukarya
+
+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.

README.md

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+# japangeoid-go
+
+日本のジオイド高を計算するための Go ライブラリ / Go library for calculating geoid height in Japan
+
+- 本ライブラリは国土地理院が提供するものではありません。
+- 本ライブラリは [ciscorn/japan-geoid](https://github.com/ciscorn/japan-geoid/tree/main) （MIT License）を参考に実装しています。
+
+対応ジオイドモデル：
+
+- 日本のジオイド 2011（Ver.2.2）（[出典](https://fgd.gsi.go.jp/download/geoid.php)）: `gsigeoid2011`
+- 日本のジオイド 2025（[出典](https://www.gsi.go.jp/buturisokuchi/grageo_reference.html)）: 正式公開後対応予定
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/eukarya-inc/japan-geoid-go/gsigeoid2011"
+)
+
+func Example() {
+	g, err := gsigeoid2011.Load()
+	if err != nil {
+		panic(err)
+	}
+
+	lng, lat := 138.2839817085188, 37.12378643088312
+	height := g.GetHeight(lng, lat)
+	fmt.Printf("Input: (lng: %.6f, lat: %.6f) -> Geoid height: %.6f\n", lng, lat, height)
+
+	lng, lat = 10, 10
+	height = g.GetHeight(lng, lat)
+	fmt.Printf("Input: (lng: %.6f, lat: %.6f) -> Geoid height: %.6f\n", lng, lat, height)
+
+	// Output:
+	// Input: (lng: 138.283982, lat: 37.123786) -> Geoid height: 39.473871
+	// Input: (lng: 10.000000, lat: 10.000000) -> Geoid height: NaN
+}
+```
+
+## Lisence
+
+[MIT Lisence](LICENSE)

cmd/conv.go

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+package main
+
+import (
+	"compress/gzip"
+	"io"
+	"net/http"
+	"os"
+	"path"
+	"strings"
+
+	japangeoid "github.com/eukarya-inc/japan-geoid-go"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		println("Usage: conv <file>")
+		os.Exit(1)
+	}
+
+	p := os.Args[1]
+	name := path.Base(p)
+
+	f, err := loadAsc(p)
+	if err != nil {
+		println(err.Error())
+		os.Exit(1)
+	}
+
+	defer f.Close()
+
+	grid, err := japangeoid.FromAsc(f)
+	if err != nil {
+		println(err.Error())
+		os.Exit(1)
+	}
+
+	f2, err := os.Create(strings.TrimSuffix(name, ".asc") + ".bin.gz")
+	if err != nil {
+		println(err.Error())
+		os.Exit(1)
+	}
+
+	defer f2.Close()
+
+	w := gzip.NewWriter(f2)
+	defer w.Close()
+
+	if err := grid.ToBinary(w); err != nil {
+		println(err.Error())
+		os.Exit(1)
+	}
+
+	println("Done")
+}
+
+func loadAsc(url string) (io.ReadCloser, error) {
+	if strings.HasPrefix(url, "http://") || strings.HasPrefix(url, "https://") {
+		req, err := http.NewRequest("GET", url, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		res, err := http.DefaultClient.Do(req)
+		if err != nil {
+			return nil, err
+		}
+
+		return res.Body, nil
+	}
+
+	return os.Open(url)
+}

gird_info.go

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+package japangeoid
+
+// GridInfo はジオイドモデルのメタデータを表します。
+type GridInfo struct {
+	XNum    uint32  // x方向グリッド数
+	YNum    uint32  // y方向グリッド数
+	XDenom  uint32  // x方向の分母 (0.025→1/0.025=40)
+	YDenom  uint32  // y方向の分母 (0.016667→1/0.016667≈60)
+	XMin    float32 // 経度の最小値
+	YMin    float32 // 緯度の最小値
+	IKind   uint16  // 未使用(ヘッダのikind)
+	Version string  // バージョン文字列
+}

go.mod

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+module github.com/eukarya-inc/japan-geoid-go
+
+go 1.24.0

grid.go

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+package japangeoid
+
+import "math"
+
+// Grid はジオイドデータを表すインターフェースです。
+type Grid interface {
+	// GetHeight は指定した経度(lng)・緯度(lat)におけるジオイドの高さを返します。
+	GetHeight(lng, lat float64) float64
+}
+
+// MemoryGrid はジオイドデータを保持する構造体です。
+type MemoryGrid struct {
+	Info   GridInfo
+	Points []int32 // グリッド点の高さ: [y_num * x_num]
+}
+
+// GetHeight は指定した経度(lng)・緯度(lat)におけるジオイドの高さを返します。無効な座標の場合は NaN を返します。
+func (g *MemoryGrid) GetHeight(lng, lat float64) float64 {
+	x, y, info := lng, lat, g.Info
+
+	// 1. convert lng, lat to grid index
+	gridX := (x - float64(info.XMin)) * float64(info.XDenom)
+	gridY := (y - float64(info.YMin)) * float64(info.YDenom)
+	if gridX < 0.0 || gridY < 0.0 {
+		return math.NaN()
+	}
+
+	ix := int(math.Floor(gridX))
+	iy := int(math.Floor(gridY))
+	if ix < 0 || iy < 0 || ix >= int(info.XNum) || iy >= int(info.YNum) {
+		return math.NaN()
+	}
+
+	// 2. get values of 4 points around
+	v00 := g.lookupGridPoints(ix, iy)
+
+	var v01 float64
+	if ix < int(info.XNum)-1 {
+		v01 = g.lookupGridPoints(ix+1, iy)
+	} else {
+		v01 = math.NaN()
+	}
+
+	var v10 float64
+	if iy < int(info.YNum)-1 {
+		v10 = g.lookupGridPoints(ix, iy+1)
+	} else {
+		v10 = math.NaN()
+	}
+
+	var v11 float64
+	if ix < int(info.XNum)-1 && iy < int(info.YNum)-1 {
+		v11 = g.lookupGridPoints(ix+1, iy+1)
+	} else {
+		v11 = math.NaN()
+	}
+
+	// 3. apply bilinear interpolation
+	xFrac := gridX - float64(ix)
+	yFrac := gridY - float64(iy)
+	return bilinear(xFrac, yFrac, v00, v01, v10, v11)
+}
+
+func (g *MemoryGrid) lookupGridPoints(ix, iy int) float64 {
+	pos := iy*int(g.Info.XNum) + ix
+	v := g.Points[pos]
+
+	// 9990000 is NaN
+	if v == 9990000 {
+		return math.NaN()
+	}
+
+	return float64(v) / 10000.0
+}

grid_test.go

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+package japangeoid
+
+import (
+	"math"
+	"testing"
+)
+
+var _ Grid = (*MemoryGrid)(nil)
+
+func TestMemoryGrid_GetHeight(t *testing.T) {
+	g := &MemoryGrid{
+		Info: GridInfo{
+			XNum:   3,
+			YNum:   3,
+			XDenom: 1,
+			YDenom: 1,
+			XMin:   0,
+			YMin:   0,
+		},
+		Points: []int32{
+			0, 1, 2,
+			3, 4, 5,
+			6, 7, 8,
+		},
+	}
+
+	tests := [][]float64{
+		{0.0, 0.0, 0.0},
+		{0.0, 1.0, 0.0003},
+		{1.0, 0.0, 0.0001},
+		{1.0, 1.0, 0.0004},
+		{2.0, 0.0, 0.0002},
+		{0.0, 2.0, 0.0006},
+		{2.0, 2.0, 0.0008},
+		{1.5, 2.0, 0.00075},
+		{-1.0, -1.0, math.NaN()},
+		{3.0, 3.0, math.NaN()},
+	}
+
+	for _, test := range tests {
+		x, y, expected := test[0], test[1], test[2]
+		h := g.GetHeight(x, y)
+
+		if math.IsNaN(expected) {
+			if !math.IsNaN(h) {
+				t.Errorf("invalid height: %v", h)
+			}
+			continue
+		}
+
+		if h != expected {
+			t.Errorf("invalid height: %v", h)
+		}
+	}
+}

gsigeoid2011/geoid2011.go

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+package gsigeoid2011
+
+import (
+	"bytes"
+	"compress/gzip"
+	_ "embed"
+	"fmt"
+
+	japangeoid "github.com/eukarya-inc/japan-geoid-go"
+)
+
+//go:embed gsigeo2011_ver2_2.bin.gz
+var geoid2011raw []byte
+
+func Load() (*japangeoid.MemoryGrid, error) {
+	b := bytes.NewReader(geoid2011raw)
+	g, err := gzip.NewReader(b)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create gzip reader: %w", err)
+	}
+
+	return japangeoid.FromBinary(g)
+}