proj4/lib/wkt.js

Proj4js is a JavaScript library to transform point coordinates from one coordinate system to another, including datum transformations.

var D2R = 0.01745329251994329577;
var extend = require('./extend');

function mapit(obj, key, v) {
  obj[key] = v.map(function(aa) {
    var o = {};
    sExpr(aa, o);
    return o;
  }).reduce(function(a, b) {
    return extend(a, b);
  }, {});
}

function sExpr(v, obj) {
  var key;
  if (!Array.isArray(v)) {
    obj[v] = true;
    return;
  }
  else {
    key = v.shift();
    if (key === 'PARAMETER') {
      key = v.shift();
    }
    if (v.length === 1) {
      if (Array.isArray(v[0])) {
        obj[key] = {};
        sExpr(v[0], obj[key]);
      }
      else {
        obj[key] = v[0];
      }
    }
    else if (!v.length) {
      obj[key] = true;
    }
    else if (key === 'TOWGS84') {
      obj[key] = v;
    }
    else {
      obj[key] = {};
      if (['UNIT', 'PRIMEM', 'VERT_DATUM'].indexOf(key) > -1) {
        obj[key] = {
          name: v[0].toLowerCase(),
          convert: v[1]
        };
        if (v.length === 3) {
          obj[key].auth = v[2];
        }
      }
      else if (key === 'SPHEROID') {
        obj[key] = {
          name: v[0],
          a: v[1],
          rf: v[2]
        };
        if (v.length === 4) {
          obj[key].auth = v[3];
        }
      }
      else if (['GEOGCS', 'GEOCCS', 'DATUM', 'VERT_CS', 'COMPD_CS', 'LOCAL_CS', 'FITTED_CS', 'LOCAL_DATUM'].indexOf(key) > -1) {
        v[0] = ['name', v[0]];
        mapit(obj, key, v);
      }
      else if (v.every(function(aa) {
        return Array.isArray(aa);
      })) {
        mapit(obj, key, v);
      }
      else {
        sExpr(v, obj[key]);
      }
    }
  }
}

function rename(obj, params) {
  var outName = params[0];
  var inName = params[1];
  if (!(outName in obj) && (inName in obj)) {
    obj[outName] = obj[inName];
    if (params.length === 3) {
      obj[outName] = params[2](obj[outName]);
    }
  }
}

function d2r(input) {
  return input * D2R;
}

function cleanWKT(wkt) {
  if (wkt.type === 'GEOGCS') {
    wkt.projName = 'longlat';
  }
  else if (wkt.type === 'LOCAL_CS') {
    wkt.projName = 'identity';
    wkt.local = true;
  }
  else {
    if (typeof wkt.PROJECTION === "object") {
      wkt.projName = Object.keys(wkt.PROJECTION)[0];
    }
    else {
      wkt.projName = wkt.PROJECTION;
    }
  }
  if (wkt.UNIT) {
    wkt.units = wkt.UNIT.name.toLowerCase();
    if (wkt.units === 'metre') {
      wkt.units = 'meter';
    }
    if (wkt.UNIT.convert) {
      wkt.to_meter = parseFloat(wkt.UNIT.convert, 10);
    }
  }

  if (wkt.GEOGCS) {
    //if(wkt.GEOGCS.PRIMEM&&wkt.GEOGCS.PRIMEM.convert){
    //  wkt.from_greenwich=wkt.GEOGCS.PRIMEM.convert*D2R;
    //}
    if (wkt.GEOGCS.DATUM) {
      wkt.datumCode = wkt.GEOGCS.DATUM.name.toLowerCase();
    }
    else {
      wkt.datumCode = wkt.GEOGCS.name.toLowerCase();
    }
    if (wkt.datumCode.slice(0, 2) === 'd_') {
      wkt.datumCode = wkt.datumCode.slice(2);
    }
    if (wkt.datumCode === 'new_zealand_geodetic_datum_1949' || wkt.datumCode === 'new_zealand_1949') {
      wkt.datumCode = 'nzgd49';
    }
    if (wkt.datumCode === "wgs_1984") {
      if (wkt.PROJECTION === 'Mercator_Auxiliary_Sphere') {
        wkt.sphere = true;
      }
      wkt.datumCode = 'wgs84';
    }
    if (wkt.datumCode.slice(-6) === '_ferro') {
      wkt.datumCode = wkt.datumCode.slice(0, - 6);
    }
    if (wkt.datumCode.slice(-8) === '_jakarta') {
      wkt.datumCode = wkt.datumCode.slice(0, - 8);
    }
    if (wkt.GEOGCS.DATUM && wkt.GEOGCS.DATUM.SPHEROID) {
      wkt.ellps = wkt.GEOGCS.DATUM.SPHEROID.name.replace('_19', '').replace(/[Cc]larke\_18/, 'clrk');
      if (wkt.ellps.toLowerCase().slice(0, 13) === "international") {
        wkt.ellps = 'intl';
      }

      wkt.a = wkt.GEOGCS.DATUM.SPHEROID.a;
      wkt.rf = parseFloat(wkt.GEOGCS.DATUM.SPHEROID.rf, 10);
    }
  }
  if (wkt.b && !isFinite(wkt.b)) {
    wkt.b = wkt.a;
  }

  function toMeter(input) {
    var ratio = wkt.to_meter || 1;
    return parseFloat(input, 10) * ratio;
  }
  var renamer = function(a) {
    return rename(wkt, a);
  };
  var list = [
    ['standard_parallel_1', 'Standard_Parallel_1'],
    ['standard_parallel_2', 'Standard_Parallel_2'],
    ['false_easting', 'False_Easting'],
    ['false_northing', 'False_Northing'],
    ['central_meridian', 'Central_Meridian'],
    ['latitude_of_origin', 'Latitude_Of_Origin'],
    ['scale_factor', 'Scale_Factor'],
    ['k0', 'scale_factor'],
    ['latitude_of_center', 'Latitude_of_center'],
    ['lat0', 'latitude_of_center', d2r],
    ['longitude_of_center', 'Longitude_Of_Center'],
    ['longc', 'longitude_of_center', d2r],
    ['x0', 'false_easting', toMeter],
    ['y0', 'false_northing', toMeter],
    ['long0', 'central_meridian', d2r],
    ['lat0', 'latitude_of_origin', d2r],
    ['lat0', 'standard_parallel_1', d2r],
    ['lat1', 'standard_parallel_1', d2r],
    ['lat2', 'standard_parallel_2', d2r],
    ['alpha', 'azimuth', d2r],
    ['srsCode', 'name']
  ];
  list.forEach(renamer);
  if (!wkt.long0 && wkt.longc && (wkt.PROJECTION === 'Albers_Conic_Equal_Area' || wkt.PROJECTION === "Lambert_Azimuthal_Equal_Area")) {
    wkt.long0 = wkt.longc;
  }
}
module.exports = function(wkt, self) {
  var lisp = JSON.parse(("," + wkt).replace(/\s*\,\s*([A-Z_0-9]+?)(\[)/g, ',["$1",').slice(1).replace(/\s*\,\s*([A-Z_0-9]+?)\]/g, ',"$1"]'));
  var type = lisp.shift();
  var name = lisp.shift();
  lisp.unshift(['name', name]);
  lisp.unshift(['type', type]);
  lisp.unshift('output');
  var obj = {};
  sExpr(lisp, obj);
  cleanWKT(obj.output);
  return extend(self, obj.output);
};