75 lines
2.4 KiB
JavaScript
75 lines
2.4 KiB
JavaScript
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import parseCode from './parseCode';
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import extend from './extend';
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import projections from './projections';
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import {sphere as dc_sphere, eccentricity as dc_eccentricity} from './deriveConstants';
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import Datum from './constants/Datum';
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import datum from './datum';
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import match from './match';
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import {getNadgrids} from "./nadgrid";
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function Projection(srsCode,callback) {
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if (!(this instanceof Projection)) {
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return new Projection(srsCode);
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}
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callback = callback || function(error){
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if(error){
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throw error;
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}
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};
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var json = parseCode(srsCode);
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if(typeof json !== 'object'){
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callback(srsCode);
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return;
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}
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var ourProj = Projection.projections.get(json.projName);
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if(!ourProj){
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callback(srsCode);
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return;
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}
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if (json.datumCode && json.datumCode !== 'none') {
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var datumDef = match(Datum, json.datumCode);
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if (datumDef) {
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json.datum_params = json.datum_params || (datumDef.towgs84 ? datumDef.towgs84.split(',') : null);
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json.ellps = datumDef.ellipse;
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json.datumName = datumDef.datumName ? datumDef.datumName : json.datumCode;
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}
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}
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json.k0 = json.k0 || 1.0;
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json.axis = json.axis || 'enu';
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json.ellps = json.ellps || 'wgs84';
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json.lat1 = json.lat1 || json.lat0; // Lambert_Conformal_Conic_1SP, for example, needs this
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var sphere_ = dc_sphere(json.a, json.b, json.rf, json.ellps, json.sphere);
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var ecc = dc_eccentricity(sphere_.a, sphere_.b, sphere_.rf, json.R_A);
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var nadgrids = getNadgrids(json.nadgrids);
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var datumObj = json.datum || datum(json.datumCode, json.datum_params, sphere_.a, sphere_.b, ecc.es, ecc.ep2,
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nadgrids);
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extend(this, json); // transfer everything over from the projection because we don't know what we'll need
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extend(this, ourProj); // transfer all the methods from the projection
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// copy the 4 things over we calculated in deriveConstants.sphere
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this.a = sphere_.a;
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this.b = sphere_.b;
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this.rf = sphere_.rf;
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this.sphere = sphere_.sphere;
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// copy the 3 things we calculated in deriveConstants.eccentricity
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this.es = ecc.es;
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this.e = ecc.e;
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this.ep2 = ecc.ep2;
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// add in the datum object
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this.datum = datumObj;
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// init the projection
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this.init();
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// legecy callback from back in the day when it went to spatialreference.org
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callback(null, this);
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}
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Projection.projections = projections;
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Projection.projections.start();
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export default Projection;
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