92 lines
2.3 KiB
JavaScript
92 lines
2.3 KiB
JavaScript
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import adjust_lon from '../common/adjust_lon';
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import asinz from '../common/asinz';
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import {EPSLN, HALF_PI} from '../constants/values';
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export function init() {
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//double temp; /* temporary variable */
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/* Place parameters in static storage for common use
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-------------------------------------------------*/
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this.sin_p14 = Math.sin(this.lat0);
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this.cos_p14 = Math.cos(this.lat0);
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}
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/* Orthographic forward equations--mapping lat,long to x,y
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---------------------------------------------------*/
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export function forward(p) {
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var sinphi, cosphi; /* sin and cos value */
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var dlon; /* delta longitude value */
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var coslon; /* cos of longitude */
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var ksp; /* scale factor */
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var g, x, y;
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var lon = p.x;
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var lat = p.y;
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/* Forward equations
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-----------------*/
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dlon = adjust_lon(lon - this.long0);
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sinphi = Math.sin(lat);
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cosphi = Math.cos(lat);
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coslon = Math.cos(dlon);
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g = this.sin_p14 * sinphi + this.cos_p14 * cosphi * coslon;
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ksp = 1;
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if ((g > 0) || (Math.abs(g) <= EPSLN)) {
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x = this.a * ksp * cosphi * Math.sin(dlon);
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y = this.y0 + this.a * ksp * (this.cos_p14 * sinphi - this.sin_p14 * cosphi * coslon);
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}
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p.x = x;
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p.y = y;
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return p;
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}
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export function inverse(p) {
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var rh; /* height above ellipsoid */
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var z; /* angle */
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var sinz, cosz; /* sin of z and cos of z */
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var con;
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var lon, lat;
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/* Inverse equations
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-----------------*/
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p.x -= this.x0;
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p.y -= this.y0;
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rh = Math.sqrt(p.x * p.x + p.y * p.y);
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z = asinz(rh / this.a);
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sinz = Math.sin(z);
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cosz = Math.cos(z);
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lon = this.long0;
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if (Math.abs(rh) <= EPSLN) {
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lat = this.lat0;
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p.x = lon;
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p.y = lat;
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return p;
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}
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lat = asinz(cosz * this.sin_p14 + (p.y * sinz * this.cos_p14) / rh);
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con = Math.abs(this.lat0) - HALF_PI;
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if (Math.abs(con) <= EPSLN) {
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if (this.lat0 >= 0) {
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lon = adjust_lon(this.long0 + Math.atan2(p.x, - p.y));
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}
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else {
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lon = adjust_lon(this.long0 - Math.atan2(-p.x, p.y));
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}
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p.x = lon;
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p.y = lat;
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return p;
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}
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lon = adjust_lon(this.long0 + Math.atan2((p.x * sinz), rh * this.cos_p14 * cosz - p.y * this.sin_p14 * sinz));
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p.x = lon;
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p.y = lat;
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return p;
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}
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export var names = ["ortho"];
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export default {
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init: init,
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forward: forward,
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inverse: inverse,
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names: names
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};
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