113 lines
3.8 KiB
Python
113 lines
3.8 KiB
Python
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BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz"
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# 邻居查找表（纬度和经度交替变化）
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NEIGHBORS = {
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"even": {
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"N": "p0r21436x8zb9dcf5h7kjnmqesgutwvy",
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"S": "14365h7k9dcfesgujnmqp0r2twvyx8zb",
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"E": "bc01fg45238967deuvhjyznpkmstqrwx",
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"W": "238967debc01fg45kmstqrwxuvhjyznp"
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},
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"odd": {
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"N": "bc01fg45238967deuvhjyznpkmstqrwx",
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"S": "238967debc01fg45kmstqrwxuvhjyznp",
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"E": "p0r21436x8zb9dcf5h7kjnmqesgutwvy",
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"W": "14365h7k9dcfesgujnmqp0r2twvyx8zb"
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}
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}
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# 边界字符（用于计算超出边界的情况）
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BORDERS = {
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"even": {"N": "prxz", "S": "028b", "E": "bcfguvyz", "W": "0145hjnp"},
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"odd": {"N": "bcfguvyz", "S": "0145hjnp", "E": "prxz", "W": "028b"}
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}
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def encode_geohash(lat, lng, precision=7):
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"""手动实现 GeoHash 编码"""
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lat_range = [-90.0, 90.0]
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lng_range = [-180.0, 180.0]
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binary = ""
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is_even = True # 纬度和经度交替编码
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while len(binary) < precision * 5:
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mid = (lng_range[0] + lng_range[1]) / 2 if is_even else (lat_range[0] + lat_range[1]) / 2
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if (lng if is_even else lat) >= mid:
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binary += "1"
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if is_even:
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lng_range[0] = mid
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else:
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lat_range[0] = mid
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else:
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binary += "0"
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if is_even:
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lng_range[1] = mid
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else:
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lat_range[1] = mid
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is_even = not is_even
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# 5 位二进制转 Base32
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return "".join(BASE32[int(binary[i:i+5], 2)] for i in range(0, len(binary), 5))
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def decode_geohash(geohash):
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"""解码 GeoHash 到 (lat, lng)"""
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lat_range = [-90.0, 90.0]
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lng_range = [-180.0, 180.0]
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binary = "".join(f"{BASE32.index(c):05b}" for c in geohash)
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is_even = True
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for bit in binary:
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if is_even:
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mid = (lng_range[0] + lng_range[1]) / 2
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lng_range = [mid, lng_range[1]] if bit == "1" else [lng_range[0], mid]
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else:
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mid = (lat_range[0] + lat_range[1]) / 2
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lat_range = [mid, lat_range[1]] if bit == "1" else [lat_range[0], mid]
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is_even = not is_even
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return (sum(lat_range) / 2, sum(lng_range) / 2)
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def get_neighbor(geohash, direction):
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"""计算 GeoHash 的单个方向邻居"""
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if not geohash:
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return None
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precision = len(geohash)
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last_char = geohash[-1] # 取最后一个字符
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geohash_prefix = geohash[:-1] # 除去最后一个字符
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is_even = (precision % 2) == 0 # 判断奇偶精度
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type_key = "even" if is_even else "odd"
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# 如果当前 GeoHash 位于边界，需要递归调整前缀
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if last_char in BORDERS[type_key][direction] and geohash_prefix:
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geohash_prefix = get_neighbor(geohash_prefix, direction)
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# 计算相邻 GeoHash
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new_last_char = BASE32[NEIGHBORS[type_key][direction].index(last_char)]
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return geohash_prefix + new_last_char
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def get_all_neighbors(geohash):
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"""计算 GeoHash 的 8 个相邻格子"""
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return {
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"N": get_neighbor(geohash, "N"),
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"S": get_neighbor(geohash, "S"),
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"E": get_neighbor(geohash, "E"),
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"W": get_neighbor(geohash, "W"),
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"NE": get_neighbor(get_neighbor(geohash, "N"), "E"),
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"NW": get_neighbor(get_neighbor(geohash, "N"), "W"),
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"SE": get_neighbor(get_neighbor(geohash, "S"), "E"),
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"SW": get_neighbor(get_neighbor(geohash, "S"), "W")
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}
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if __name__ == '__main__':
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# 示例：计算北京天安门广场（39.9087, 116.3975）的邻居
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gh = encode_geohash(39.9087, 116.3975, precision=7)
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neighbors = get_all_neighbors(gh)
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print(f"中心 GeoHash: {gh}, {decode_geohash(gh)}")
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print("相邻 GeoHash:")
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for direction, neighbor in neighbors.items():
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print(f"{direction}: {neighbor}, {decode_geohash(neighbor)}")
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