var PJD_3PARAM = 1;
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var PJD_7PARAM = 2;
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var PJD_GRIDSHIFT = 3;
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var PJD_NODATUM = 5; // WGS84 or equivalent
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var SRS_WGS84_SEMIMAJOR = 6378137; // only used in grid shift transforms
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var SRS_WGS84_ESQUARED = 0.006694379990141316; //DGR: 2012-07-29
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module.exports = function(source, dest, point) {
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var wp, i, l;
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function checkParams(fallback) {
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return (fallback === PJD_3PARAM || fallback === PJD_7PARAM);
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}
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// Short cut if the datums are identical.
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if (source.compare_datums(dest)) {
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return point; // in this case, zero is sucess,
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// whereas cs_compare_datums returns 1 to indicate TRUE
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// confusing, should fix this
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}
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// Explicitly skip datum transform by setting 'datum=none' as parameter for either source or dest
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if (source.datum_type === PJD_NODATUM || dest.datum_type === PJD_NODATUM) {
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return point;
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}
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//DGR: 2012-07-29 : add nadgrids support (begin)
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var src_a = source.a;
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var src_es = source.es;
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var dst_a = dest.a;
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var dst_es = dest.es;
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var fallback = source.datum_type;
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// If this datum requires grid shifts, then apply it to geodetic coordinates.
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if (fallback === PJD_GRIDSHIFT) {
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if (this.apply_gridshift(source, 0, point) === 0) {
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source.a = SRS_WGS84_SEMIMAJOR;
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source.es = SRS_WGS84_ESQUARED;
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}
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else {
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// try 3 or 7 params transformation or nothing ?
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if (!source.datum_params) {
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source.a = src_a;
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source.es = source.es;
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return point;
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}
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wp = 1;
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for (i = 0, l = source.datum_params.length; i < l; i++) {
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wp *= source.datum_params[i];
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}
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if (wp === 0) {
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source.a = src_a;
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source.es = source.es;
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return point;
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}
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if (source.datum_params.length > 3) {
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fallback = PJD_7PARAM;
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}
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else {
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fallback = PJD_3PARAM;
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}
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}
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}
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if (dest.datum_type === PJD_GRIDSHIFT) {
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dest.a = SRS_WGS84_SEMIMAJOR;
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dest.es = SRS_WGS84_ESQUARED;
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}
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// Do we need to go through geocentric coordinates?
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if (source.es !== dest.es || source.a !== dest.a || checkParams(fallback) || checkParams(dest.datum_type)) {
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//DGR: 2012-07-29 : add nadgrids support (end)
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// Convert to geocentric coordinates.
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source.geodetic_to_geocentric(point);
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// CHECK_RETURN;
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// Convert between datums
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if (checkParams(source.datum_type)) {
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source.geocentric_to_wgs84(point);
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// CHECK_RETURN;
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}
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if (checkParams(dest.datum_type)) {
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dest.geocentric_from_wgs84(point);
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// CHECK_RETURN;
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}
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// Convert back to geodetic coordinates
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dest.geocentric_to_geodetic(point);
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// CHECK_RETURN;
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}
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// Apply grid shift to destination if required
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if (dest.datum_type === PJD_GRIDSHIFT) {
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this.apply_gridshift(dest, 1, point);
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// CHECK_RETURN;
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}
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source.a = src_a;
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source.es = src_es;
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dest.a = dst_a;
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dest.es = dst_es;
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return point;
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};
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