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    spatialreference

    1.1.3 • Public • Published

    SpatialReference

    A helper library for translating between spatial reference systems

    npm version build status

    Usage

    Basic installation: npm install spatialreference

    Then to use the module: var SR = require('spatialreference')

    With a DB

    To use this module with a db that can store or retrieve WKTs, it needs to support (or be wrapped to support) two functions:

    function getWKT (wkid, function (err, wkt) {
    // do some stuff to get a wkt
    callback(null, wkt)
    })
    function insertWKT (wkid, wkt, function (err) {
    // store the wkt in the db
    callback(null)
    })

    Then initialize the SpatialReference object with a db in the options.db key

    var SR = require('spatialreference')
    var db = require('koop-pgcache') // or your db that supports getWKT and insertWKT
    var sr = new SR({db: db})

    With a logger

    By default SpatialReference will log to the console, but you can optionally pass in a logger in the options key. It needs to support a function like:

    function log('level','message') {
    // write a log!
    }
    var SR = require('spatialreference')
    var logger = require('winston')
    var sr = new SR({logger: logger})

    API

    wkidToWkt

    This method takes a spatial reference system well-known id and gets the well-known text. If the WKID is an esri code, then it will use the esri-proj-codes library. If the WKID is available in a passed in database it will get it from there. Else it will make a request to http://www.epsg.io, insert the WKT into the database and return it to the client.

    Example using koop-pgcache

    var SpatialReference = require('spatialreference')
    var db = require('koop-pgcache')
     
    var sr = new SpatialReference({db: db})
     
    sr.wkidToWkt(2927, function (err, wkt) {
        if (err) return console.error(err)
        console.log(wkt) 
        // 'PROJCS["NAD83(HARN) / Washington South (ftUS)",GEOGCS["NAD83(HARN)",DATUM["NAD83_High_Accuracy_Regional_Network",SPHEROID["GRS 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6152"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4152"]],UNIT["US survey foot",0.3048006096012192,AUTHORITY["EPSG","9003"]],PROJECTION["Lambert_Conformal_Conic_2SP"],PARAMETER["standard_parallel_1",47.33333333333334],PARAMETER["standard_parallel_2",45.83333333333334],PARAMETER["latitude_of_origin",45.33333333333334],PARAMETER["central_meridian",-120.5],PARAMETER["false_easting",1640416.667],PARAMETER["false_northing",0],AUTHORITY["EPSG","2927"],AXIS["X",EAST],AXIS["Y",NORTH]]'
    })

    esriLookup

    This is a pure wrapper around the esri-proj-codes library. It gets the esri format of the well-known text for a projection when given the well-known id.

    var SpatialReference = require('spatialreference')
     
    var sr = new SpatialReference()
     
    sr.esriLookup(2927, function (err, wkt) {
        if (err) return console.error(err)
        console.log(wkt) 
        // PROJCS["NAD_1983_HARN_StatePlane_Washington_South_FIPS_4602_Feet",GEOGCS["GCS_North_American_1983_HARN",DATUM["D_North_American_1983_HARN",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",1640416.666666667],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-120.5],PARAMETER["Standard_Parallel_1",45.83333333333334],PARAMETER["Standard_Parallel_2",47.33333333333334],PARAMETER["Latitude_Of_Origin",45.33333333333334],UNIT["Foot_US",0.3048006096012192]]
    })

    Acknowledgements

    This module leans heavily on the spatial reference information saved in PostGIS and the data available at epsg.io. It would not be possible without those two resources. So thank you to all involved.

    Install

    npm i spatialreference

    DownloadsWeekly Downloads

    80

    Version

    1.1.3

    License

    Apache-2.0

    Unpacked Size

    85.5 kB

    Total Files

    12

    Last publish

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