circle-to-polygon
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    2.2.0 • Public • Published

    Circle To Polygon

    The GeoJSON spec does not support circles. If you wish to create an area that represents a circle, your best bet is to create a polygon that roughly approximates the circle. In the limit of the number of edges becoming infinite, your Polygon will match a circle.

    Installation

    npm install --save circle-to-polygon

    or

    yarn add circle-to-polygon

    Usage

    Example

    const circleToPolygon = require("circle-to-polygon");
    
    const coordinates = [-27.4575887, -58.99029]; //[lon, lat]
    const radius = 100; // in meters
    const numberOfEdges = 32; //optional that defaults to 32
    
    let polygon = circleToPolygon(coordinates, radius, numberOfEdges);
    
    /*
     *
    polygon:
     
     type = 'Polygon'
     coordinates = [ [ [ -27.457588699999995, -58.98939168471588 ],
                        [ -27.457248533454194, -58.98940894514629 ],
                        [ -27.456921438327615, -58.9894600631796 ],
                        [ -27.45661998386292, -58.98954307452298 ],
                        [ -27.4563557542251, -58.989654789313285 ],
                        [ -27.456138903413915, -58.98979091466893 ],
                        [ -27.45597776508136, -58.98994621962397 ],
                        [ -27.45587853224417, -58.99011473611232 ],
                        [ -27.455845019204208, -58.99028998828441 ],
                        [ -27.455878514839235, -58.99046524134828 ],
                        [ -27.455977732921237, -58.99063376037627 ],
                        [ -27.456138861394688, -58.99078906913211 ],
                        [ -27.456355708743818, -58.990925198971134 ],
                        [ -27.45661994184369, -58.99103691824481 ],
                        [ -27.45692140616749, -58.99111993338897 ],
                        [ -27.457248516049262, -58.99117105396192 ],
                        [ -27.457588699999995, -58.99118831528412 ],
                        [ -27.45792888395073, -58.99117105396192 ],
                        [ -27.458255993832502, -58.99111993338897 ],
                        [ -27.458557458156303, -58.99103691824481 ],
                        [ -27.458821691256173, -58.990925198971134 ],
                        [ -27.459038538605306, -58.99078906913211 ],
                        [ -27.45919966707875, -58.99063376037627 ],
                        [ -27.459298885160756, -58.99046524134828 ],
                        [ -27.459332380795786, -58.99028998828441 ],
                        [ -27.459298867755823, -58.99011473611232 ],
                        [ -27.459199634918626, -58.98994621962397 ],
                        [ -27.45903849658608, -58.98979091466893 ],
                        [ -27.45882164577489, -58.989654789313285 ],
                        [ -27.458557416137072, -58.98954307452298 ],
                        [ -27.45825596167238, -58.9894600631796 ],
                        [ -27.4579288665458, -58.98940894514629 ],
                        [ -27.457588699999995, -58.98939168471588 ] ] ]
    */

    Parameters

    • coordinates Array of length 2 or 3 *required
      • First Element: longitude Number *required, can be any number <=180 and >=-180
      • Second Element: latitude Number *required, can be any number <=90 and >=-90
      • Third Element: Ignored if present
    • radius Number *required, can be any number >0
    • numberOfEdges Number can be any number >=3, defaults to 32 when undefined
    • earthRadius Number can be any number >0, defaults to 6378137 (equatorial Earth radius) when undefined
    • bearing Number can be any number, defaults to 0 when undefined

    Disclaimers

    • Decimal values will not throw error for numberOfEdges! Instead one of the edges of the polygon will be smaller than the others. In other words, all edges will not have the same length if a decimal number is passed as numberOfEdges.
    • A circle whoes edge cross longitude edges (-180 or 180) or a latitude edge (-90 or 90) will contain coordinate points that are outside the stanardized coordinates (eg: [182, 23]). This is because there are two ways to represent a line going from [179, x] to [181, y]. One way is simply writing it as [[179, x], [182, y]] while the other is to write it as a multi-polygon. Version <= 2.0.x does only support the first way while release of 2.1.0 will support multi-polygons as well.

    Authors

    • Gabriel Zimmermann
    • Johannes Jarbratt

    Contributors

    • Jan Žák

    License

    ISC

    Install

    npm i circle-to-polygon

    DownloadsWeekly Downloads

    6,567

    Version

    2.2.0

    License

    ISC

    Unpacked Size

    44.1 kB

    Total Files

    13

    Last publish

    Collaborators

    • gabzim