https://github.com/andrerav/geohash.polyhasher
A .NET library and command line tool that converts geometries such as polygons and linestrings to optimized sets of geohashes.
https://github.com/andrerav/geohash.polyhasher
Last synced: 23 days ago
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A .NET library and command line tool that converts geometries such as polygons and linestrings to optimized sets of geohashes.
- Host: GitHub
- URL: https://github.com/andrerav/geohash.polyhasher
- Owner: andrerav
- License: mit
- Created: 2021-10-03T21:41:56.000Z (almost 5 years ago)
- Default Branch: main
- Last Pushed: 2021-10-15T19:41:53.000Z (over 4 years ago)
- Last Synced: 2025-02-10T04:18:22.869Z (over 1 year ago)
- Language: C#
- Size: 46.9 KB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Geohash.PolyHasher
# Introduction
Geohash.Polyhasher is a .NET library and command line tool that converts geometries such as polygons and linestrings to optimized sets of geohashes. Try it out over at [https://lab.ramn.no/Tools/PolyHasher](https://lab.ramn.no/Tools/PolyHasher).
# Download
| Package | Link | Description |
| ------- | ---- | ----------- |
| Geohash.Polyhasher | [](https://www.nuget.org/packages/Geohash.Polyhasher/) | Use this package to install Polyhasher as a library in your C#/.NET project. |
| Geohash.Polyhasher.CLI | [](https://www.nuget.org/packages/Geohash.Polyhasher.CLI/) | Use this package to install Polyhasher as a dotnet command line tool (see [CLI quickstart](#command-line-quickstart) below). You can install this tool using the command `dotnet tool install --global Geohash.Polyhasher.CLI`. |
# Description
Geohash.Polyhasher is a tool that can convert geometries such as linestrings, polygons, multipolygons and more to well-optimized sets of geohashes. If you are not familiar with the concept of geohashing, then you may want to familiarize yourself with the concept of geohashes first, and then come back here.
To understand what this library does, please look at this illustration that shows the input and output from this library:
_TODO_
# What can you do with Polyhasher?
This library is useful if you are working with spatial data and need to make computations such as finding all points within a polygon, but without using a spatial database and still retaining excellent performance. By encoding geometries as geohashes and using a prefix tree for lookup, you can achieve performance that is on par or better than using geospatial databases.
# API Quickstart
The following example can be pasted directly into Program.cs in a .NET 6.0 or newer console application:
```csharp
using Geohash.Polyhasher;
using NetTopologySuite.IO;
// Define the polygon we wish to encode
var polygon = new WKTReader().Read("MULTIPOLYGON (((40 40, 20 45, 45 30, 40 40)), " +
"((20 35, 45 20, 30 5, 10 10, 10 30, 20 35), " +
"(30 20, 20 25, 20 15, 30 20)))");
// Create a new polyhasher instance
var polyhasher = new Polyhasher();
// Returns a HashSet of 27 geohashes which encodes the multipolygon specified above
var geohashes = polyhasher.Encode(polygon, 2, PolyhasherMode.Intersects);
```
Also see the provided [example project](https://github.com/andrerav/Geohash.PolyHasher/tree/main/src/Geohash.Polyhasher/Geohash.Polyhasher.Example).
## API documentation
[The full API documentation is available here](https://github.com/andrerav/Geohash.PolyHasher/tree/main/docs/MANUAL.md).
# Command line quickstart
Install the CLI as a global .NET tool:
```bash
dotnet tool install --global Geohash.Polyhasher.CLI
```
Check the available options:
```bash
polyhasher --help
```
Encode a polygon from standard input (WKT):
```bash
echo "POLYGON ((10 10, 12 10, 12 12, 10 12, 10 10))" | polyhasher -p 6 -m Intersects -e Planar
```
Encode from a file instead of stdin:
```bash
polyhasher -f polygon.wkt -p 6 -m Intersects -e Planar
```
Use `Contains` mode (only hashes fully contained by the geometry):
```bash
polyhasher -f polygon.wkt -p 6 -m Contains -e Planar
```
Use geodesic edge handling (useful for large or long-distance geometries on the globe):
```bash
polyhasher -f polygon.wkt -p 6 -m Intersects -e Geodesic
```
Use densified edge handling (linearly densifies edges before relation checks):
```bash
polyhasher -f polygon.wkt -p 6 -m Intersects -e Densified
```
Output geohashes together with each hash cell geometry as CSV:
```bash
polyhasher -f polygon.wkt -p 6 -m Intersects -e Planar -g true -h true -s ";"
```
Notes:
- Supported input format is WKT.
- If `-f` is omitted, input is read from standard input.
- Precision (`-p`) must be between 1 and 12.
- Edge handling (`-e`) supports `Planar`, `Densified`, and `Geodesic`.