Geohash Visualizer

What is Geohashing?

Geohash is a public domain geocoding system which encodes a geographic location (latitude and longitude) into a short string of letters and digits (alphanumeric). It's a hierarchical spatial data structure which subdivides space into buckets of grid shape, which is one of the many applications of what is known as a space-filling curve.

The key idea is that geohashes represent rectangular areas, and longer geohashes represent smaller, more precise areas nested within the area of their prefix.

Why Use Geohashing?

• Proximity Searches: Geohashes of nearby locations often share long common prefixes. This allows for efficient database queries to find points near a given location (e.g., "find all restaurants whose geohash starts with `u4pru`").
• Database Indexing: Geohash strings can be used as index keys in traditional databases, enabling spatial queries on systems that don't natively support them well.
• Concise Representation: Provides a short, human-readable (ish) string representation of a location.

How It Works (Conceptual Algorithm)

Geohashing uses a process of iterative binary partitioning of the latitude and longitude ranges, interleaving the bits, and then encoding using Base32.

1. Define Ranges: Start with the full Earth ranges: Longitude [-180, 180] and Latitude [-90, 90].
2. Iterative Partitioning:
   • For a desired precision (length of the final hash), repeat the following steps, alternating between longitude and latitude:
   • Calculate the midpoint of the current longitude/latitude range.
   • If the point's coordinate is greater than or equal to the midpoint, assign a bit '1' and narrow the range to the upper half.
   • If the point's coordinate is less than the midpoint, assign a bit '0' and narrow the range to the lower half.
3. Interleave Bits: Combine the longitude and latitude bits, alternating between them (e.g., `lon_bit0, lat_bit0, lon_bit1, lat_bit1, ...`).
4. Group into 5-bit Chunks: Divide the interleaved binary string into groups of 5 bits.
5. Base32 Encode: Convert each 5-bit chunk (representing a number 0-31) into its corresponding character using a specific Base32 character map (0-9, b-z, excluding 'a', 'i', 'l', 'o').

The final string of Base32 characters is the geohash. Longer strings provide higher precision (smaller bounding boxes).

Key Property: As mentioned, nearby points tend to have longer common prefixes in their geohash strings. This is because they often fall into the same larger bounding boxes during the initial partitioning steps.

Limitation: Points very close to each other but on opposite sides of a major division boundary (like the equator or prime meridian, or subsequent midpoints) might have very different geohashes, which is a known edge case.

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