https://github.com/Willyham/hashfill

Fill geofences with geohashes
https://github.com/Willyham/hashfill

geofences geohash golang golang-package

Last synced: 7 days ago
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Fill geofences with geohashes

• Host: GitHub
• URL: https://github.com/Willyham/hashfill
• Owner: Willyham
• License: mit
• Created: 2017-11-10T11:56:58.000Z (about 7 years ago)
• Default Branch: master
• Last Pushed: 2024-01-27T05:33:34.000Z (10 months ago)
• Last Synced: 2024-08-01T19:45:08.929Z (3 months ago)
• Topics: geofences, geohash, golang, golang-package
• Language: Go
• Size: 1.2 MB
• Stars: 41
• Watchers: 0
• Forks: 12
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
[![GoDoc](http://godoc.org/github.com/Willyham/hashfill?status.png)](http://godoc.org/github.com/Willyham/hashfill) [![Go Report Card](https://goreportcard.com/badge/github.com/Willyham/hashfill)](https://goreportcard.com/report/github.com/Willyham/hashfill)

## Usage

Hashfill is a library for computing the set of geohashes which are contained by a geofence. It can either produce a set

of hashes which are completely contained or one which also includes where the boundaries intersect. It currently operates on

`geom.Polygon` objects from the [https://github.com/twpayne/go-geom](go-geom) pacakge. Converting from geojson is simple and this

package may offer a utility in the future.

```golang

func readFileAsGeometry(t *testing.T, file string) (*geom.Polygon, error) {

	data, err := ioutil.ReadFile(file)

	if err != nil {

		return nil, err

	}

	poly := new(geom.T)

	err = geojson.Unmarshal(data, poly)

	if err != nil {

		return nil, err

	}

	return nil, (*poly).(*geom.Polygon)

}

geofence := readFileAsGeometry("testdata/regents.geojson")

filler := hashfill.NewRecursiveFiller(

  hashfill.WithMaxPrecision(8),

)

hashes, err := filler.Fill(geofence, hashfill.FillIntersects)

```

Would result in something that could be visualized as:

![](./doc/fill.png)

### Installation

This library depends on headers from the `geos` library. You can install with `brew install geos` or `dnf install geos-devel` on RPM based linux distros.

### Options

- `WithMaxPrecision` - Sets the max hash precision the algorithm will generate hashes for.

- `WithFixedPrecision` - Causes the fully contained geohashes to still be divided into the hashes of the max precision.

- `WithPredicates` - Can be used to supply your own functions for `Intersect` and `Contains` rather than the built in ones.

### Improvements

TODO:

- [] Fix bug in geofences with holes.

- [] Corner based check optimisations (+ hybrid)

- [] Cache poly to geom operation in predicates.

- [] Add benchmarks