Initial Commit

packages/geospatial/geo/geo-earth/src/geohash/geohash.ts

@@ -0,0 +1,85 @@
+const BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz";
+
+export function encodeGeohash(
+    coord: { latitude: number; longitude: number },
+    precision = 9
+): string {
+    let minLat = -90;
+    let maxLat = 90;
+    let minLon = -180;
+    let maxLon = 180;
+    let hash = "";
+    let bits = 0;
+    let ch = 0;
+    let evenBit = true;
+
+    while (hash.length < precision) {
+        if (evenBit) {
+            const mid = (minLon + maxLon) / 2;
+            if (coord.longitude >= mid) {
+                ch = (ch << 1) | 1;
+                minLon = mid;
+            } else {
+                ch = ch << 1;
+                maxLon = mid;
+            }
+        } else {
+            const mid = (minLat + maxLat) / 2;
+            if (coord.latitude >= mid) {
+                ch = (ch << 1) | 1;
+                minLat = mid;
+            } else {
+                ch = ch << 1;
+                maxLat = mid;
+            }
+        }
+        evenBit = !evenBit;
+        bits++;
+        if (bits === 5) {
+            hash += BASE32[ch];
+            bits = 0;
+            ch = 0;
+        }
+    }
+
+    return hash;
+}
+
+export function decodeGeohash(hash: string): {
+    latitude: number;
+    longitude: number;
+} {
+    let minLat = -90;
+    let maxLat = 90;
+    let minLon = -180;
+    let maxLon = 180;
+    let evenBit = true;
+
+    for (const char of hash) {
+        const idx = BASE32.indexOf(char);
+        for (let i = 4; i >= 0; i--) {
+            const bit = (idx >> i) & 1;
+            if (evenBit) {
+                const mid = (minLon + maxLon) / 2;
+                if (bit === 1) {
+                    minLon = mid;
+                } else {
+                    maxLon = mid;
+                }
+            } else {
+                const mid = (minLat + maxLat) / 2;
+                if (bit === 1) {
+                    minLat = mid;
+                } else {
+                    maxLat = mid;
+                }
+            }
+            evenBit = !evenBit;
+        }
+    }
+
+    return {
+        latitude: (minLat + maxLat) / 2,
+        longitude: (minLon + maxLon) / 2,
+    };
+}