Recursive Geohash Neighboring Ring Finder

Overview

This Python script provides a solution to find neighboring geohashes in a recursive manner, forming concentric rings around a given center geohash cell. The primary motivation behind creating this script was the unavailability of an existing tool or library that could efficiently find geohashes within multiple rings surrounding a central geohash.

Background

Geohashes are a widely used system to represent geographic coordinates as short strings, allowing spatial indexing and proximity-based searches. While finding immediate neighbors of a geohash cell is a standard feature in many geospatial libraries, finding neighboring geohashes in concentric rings up to a specified depth or level is a more specialized requirement.

How It Works

The script leverages the geolib library to find the immediate neighbors of a given geohash cell. It takes the center geohash and user-specified ring level as input, which determines the number of rings surrounding the central geohash to be found. The output is a list of geohashes that form these concentric rings.

Complete Code

from geolib import geohash

def get_neighbouring_ring(level: int, hashes: list):
    try:
        if not isinstance(level, int) or level <= 0:
            raise ValueError("Level must be a positive integer greater than 0.")
        
        if not isinstance(hashes, list) or not all(isinstance(h, str) for h in hashes):
            raise ValueError("Hashes must be a list of strings.")

        visited = set(hashes)
        queue = hashes.copy()
        next_level_items = []

        while level > 0:
            for hash in queue:
                neighbors = geohash.neighbours(hash)
                next_level_items.extend(neighbors)
                visited.update(neighbors)

            queue = next_level_items.copy()
            next_level_items.clear()
            level -= 1

        return list(visited)

    except ValueError as e:
        print(f"Error: {e}")
        return []

# Test example:
level = 2   # input the depth of the ring
hashes = ['dpxtp']   # include only the center geohash of the ring

ring = get_neighbouring_ring(level, hashes)
print(ring)

Usage

To use the script, you need to have Python installed along with the geolib library. You can install the library using the following command:

pip install geolib

Then, simply copy and paste the provided Python script into your project or create a new Python file with this content.

Function Signature

def get_neighbouring_ring(level: int, hashes: list) -> list:

Parameters

• level (int): The depth of the ring, i.e., the number of concentric rings to be formed around the center geohash.
• hashes (list of str): A list containing the center geohash around which the rings will be formed.

Return

The function returns a list of geohashes, including the center geohash and all neighboring geohashes within the specified number of concentric rings.

Test Example

level = 2   # input the depth of the ring
hashes = ['dpxtp']   # include only the center geohash of the ring

ring = get_neighbouring_ring(level, hashes)
print(ring)

Important Notes

• Ensure that you have the geolib library installed before running the script.
• The level parameter must be a positive integer greater than 0, and hashes must be a list of strings.
• In case of incorrect inputs, the script will handle errors and return an empty list.
• You may use site 1 and site 2 to visualize geohash on the map.

You can find the complete code in my GitHub repository.