Nourishing Pizza Microservice

    shape2geohash

    1.2.5 • Public • Published

    codecov npm version Build Status

    shape2geohash

    A small library that turns any GeoJSON shape into a list of geohashes.

    Installation

    npm install shape2geohash
    

    Usage

    const shape2geohash = require("shape2geohash")
     
    // Providing polygon as GeoJSON
    const geohashes1 = await shape2geohash({
      type: "Polygon",
      coordinates: [
        [
          [13.0, 52.5], //[long, lat]
          [13.3, 52.5],
          [13.3, 52.2],
          [13.0, 52.2],
          [13.0, 52.5], // make sure the last coordinate is equal to the first one
        ]
      ]
    })
     
    // returns ["u336xp", etc.]
     
     
    // Providing polygon as an array of coordinates
    const geohashes2 = await shape2geohash([
      [
        [13.0, 52.5], //[long, lat]
        [13.3, 52.5],
        [13.3, 52.2],
        [13.0, 52.2],
        [13.0, 52.5], // make sure the last coordinate is equal to the first one
      ]
    ])
     
    // returns ["u336xp", etc.]

    shape2geohash(geoJSON, options)

    • geoJSON can be any of these things:
      • Any GeoJSON object of the following type:
        • FeatureCollection
        • Feature
        • Polygon
        • MultiPolygon
        • LineString
        • MultiLineString
        • Point
        • MultiPoint
      • A single polygon as a simple array of coordinates
      • An array of polygons

    Returns a promise that resolves to an array of geohashes that intersect with the given shape(s)

    Options

    const defaultOptions = {
      precision: 6,
      hashMode: "intersect",
      minIntersect: 0,
      allowDuplicates: true,
      customWriter: null
    }
    • precision: Length of the returned geohashes. Also known as geohash level (Level 6 geohash = u336dc)
    • hashMode: Determines what kind of hashes are being included. Available modes are:
      • intersect: Includes all geohashes that intersect with the shape.
      • envelope: Includes all geohashes that are inside the rectangular border of the shape.
      • insideOnly: Includes only the geohashes that are fully within the polygon.
      • border: Includes only the geohashes that intersect with the border of the polygon.
    • minIntersect: Percentage value between 0 and 1. Defines the minimum area of a geohash that needs to be covered by the polygon to be included in the geohash list. This is only relevant for the edge of the polygon when using the hashMode intersect.
    • allowDuplicates: Determines if the output array may contain duplicate geohashes. These can occur when, for example, multiple polygons overlap.
    • customWriter: Custom Writable Stream that can used for custom stream processing. See Custom Stream Processing section for more details.

    Custom Stream Processing

    This package uses Node.js Streams to process the incoming shape row-wise from top to bottom. You can substitute the internally used Writable Stream with your custom Writable Stream. This may be useful if you want to process extremely large polygons.

    You need to implement the write method to receive the data. The data passed into the write method will be all geohashes that are in the current row from top to bottom.

    Since the incoming data is always an array you MUST enable objectMode!

    const Stream = require("stream")
     
    const myGeohashes = []
    const myCustomWriter = new Stream.Writable({
      objectMode: true, // THIS IS IMPORTANT
      write: (rowGeohashes, enc, callback) => {
        // rowGeohashes = ["u336xp", ...]
        // Do some processing with the incoming geohashes per row
        myGeohashes.push(...rowGeohashes)
        callback()
      },
    })
     
    shape2geohash(polygon, { 
      customWriter: myCustomWriter,
      // ...other options
    })

    Testing

    run npm test

    Afterwards you can open the index.html in test/visualization to see a visualization of the test.

    Install

    npm i shape2geohash

    DownloadsWeekly Downloads

    236

    Version

    1.2.5

    License

    MIT

    Unpacked Size

    219 kB

    Total Files

    15

    Last publish

    Collaborators

    • marcelreppi