|
// Initialize the Stereographic projection
|
|
Proj4js.Proj.stere = {
|
ssfn_: function(phit, sinphi, eccen) {
|
sinphi *= eccen;
|
return (Math.tan (.5 * (Proj4js.common.HALF_PI + phit)) * Math.pow((1. - sinphi) / (1. + sinphi), .5 * eccen));
|
},
|
TOL: 1.e-8,
|
NITER: 8,
|
CONV: 1.e-10,
|
S_POLE: 0,
|
N_POLE: 1,
|
OBLIQ: 2,
|
EQUIT: 3,
|
|
init: function() {
|
this.phits = this.lat_ts ? this.lat_ts : Proj4js.common.HALF_PI;
|
var t = Math.abs(this.lat0);
|
if ((Math.abs(t) - Proj4js.common.HALF_PI) < Proj4js.common.EPSLN) {
|
this.mode = this.lat0 < 0. ? this.S_POLE : this.N_POLE;
|
} else {
|
this.mode = t > Proj4js.common.EPSLN ? this.OBLIQ : this.EQUIT;
|
}
|
this.phits = Math.abs(this.phits);
|
if (this.es) {
|
var X;
|
|
switch (this.mode) {
|
case this.N_POLE:
|
case this.S_POLE:
|
if (Math.abs(this.phits - Proj4js.common.HALF_PI) < Proj4js.common.EPSLN) {
|
this.akm1 = 2. * this.k0 / Math.sqrt(Math.pow(1+this.e,1+this.e)*Math.pow(1-this.e,1-this.e));
|
} else {
|
t = Math.sin(this.phits);
|
this.akm1 = Math.cos(this.phits) / Proj4js.common.tsfnz(this.e, this.phits, t);
|
t *= this.e;
|
this.akm1 /= Math.sqrt(1. - t * t);
|
}
|
break;
|
case this.EQUIT:
|
this.akm1 = 2. * this.k0;
|
break;
|
case this.OBLIQ:
|
t = Math.sin(this.lat0);
|
X = 2. * Math.atan(this.ssfn_(this.lat0, t, this.e)) - Proj4js.common.HALF_PI;
|
t *= this.e;
|
this.akm1 = 2. * this.k0 * Math.cos(this.lat0) / Math.sqrt(1. - t * t);
|
this.sinX1 = Math.sin(X);
|
this.cosX1 = Math.cos(X);
|
break;
|
}
|
} else {
|
switch (this.mode) {
|
case this.OBLIQ:
|
this.sinph0 = Math.sin(this.lat0);
|
this.cosph0 = Math.cos(this.lat0);
|
case this.EQUIT:
|
this.akm1 = 2. * this.k0;
|
break;
|
case this.S_POLE:
|
case this.N_POLE:
|
this.akm1 = Math.abs(this.phits - Proj4js.common.HALF_PI) >= Proj4js.common.EPSLN ?
|
Math.cos(this.phits) / Math.tan(Proj4js.common.FORTPI - .5 * this.phits) :
|
2. * this.k0 ;
|
break;
|
}
|
}
|
},
|
|
// Stereographic forward equations--mapping lat,long to x,y
|
forward: function(p) {
|
var lon = p.x;
|
lon = Proj4js.common.adjust_lon(lon - this.long0);
|
var lat = p.y;
|
var x, y;
|
|
if (this.sphere) {
|
var sinphi, cosphi, coslam, sinlam;
|
|
sinphi = Math.sin(lat);
|
cosphi = Math.cos(lat);
|
coslam = Math.cos(lon);
|
sinlam = Math.sin(lon);
|
switch (this.mode) {
|
case this.EQUIT:
|
y = 1. + cosphi * coslam;
|
if (y <= Proj4js.common.EPSLN) {
|
Proj4js.reportError("stere:forward:Equit");
|
}
|
y = this.akm1 / y;
|
x = y * cosphi * sinlam;
|
y *= sinphi;
|
break;
|
case this.OBLIQ:
|
y = 1. + this.sinph0 * sinphi + this.cosph0 * cosphi * coslam;
|
if (y <= Proj4js.common.EPSLN) {
|
Proj4js.reportError("stere:forward:Obliq");
|
}
|
y = this.akm1 / y;
|
x = y * cosphi * sinlam;
|
y *= this.cosph0 * sinphi - this.sinph0 * cosphi * coslam;
|
break;
|
case this.N_POLE:
|
coslam = -coslam;
|
lat = -lat;
|
//Note no break here so it conitnues through S_POLE
|
case this.S_POLE:
|
if (Math.abs(lat - Proj4js.common.HALF_PI) < this.TOL) {
|
Proj4js.reportError("stere:forward:S_POLE");
|
}
|
y = this.akm1 * Math.tan(Proj4js.common.FORTPI + .5 * lat);
|
x = sinlam * y;
|
y *= coslam;
|
break;
|
}
|
} else {
|
coslam = Math.cos(lon);
|
sinlam = Math.sin(lon);
|
sinphi = Math.sin(lat);
|
var sinX, cosX;
|
if (this.mode == this.OBLIQ || this.mode == this.EQUIT) {
|
var Xt = 2. * Math.atan(this.ssfn_(lat, sinphi, this.e));
|
sinX = Math.sin(Xt - Proj4js.common.HALF_PI);
|
cosX = Math.cos(Xt);
|
}
|
switch (this.mode) {
|
case this.OBLIQ:
|
var A = this.akm1 / (this.cosX1 * (1. + this.sinX1 * sinX + this.cosX1 * cosX * coslam));
|
y = A * (this.cosX1 * sinX - this.sinX1 * cosX * coslam);
|
x = A * cosX;
|
break;
|
case this.EQUIT:
|
var A = 2. * this.akm1 / (1. + cosX * coslam);
|
y = A * sinX;
|
x = A * cosX;
|
break;
|
case this.S_POLE:
|
lat = -lat;
|
coslam = - coslam;
|
sinphi = -sinphi;
|
case this.N_POLE:
|
x = this.akm1 * Proj4js.common.tsfnz(this.e, lat, sinphi);
|
y = - x * coslam;
|
break;
|
}
|
x = x * sinlam;
|
}
|
p.x = x*this.a + this.x0;
|
p.y = y*this.a + this.y0;
|
return p;
|
},
|
|
|
//* Stereographic inverse equations--mapping x,y to lat/long
|
inverse: function(p) {
|
var x = (p.x - this.x0)/this.a; /* descale and de-offset */
|
var y = (p.y - this.y0)/this.a;
|
var lon, lat;
|
|
var cosphi, sinphi, tp=0.0, phi_l=0.0, rho, halfe=0.0, pi2=0.0;
|
var i;
|
|
if (this.sphere) {
|
var c, rh, sinc, cosc;
|
|
rh = Math.sqrt(x*x + y*y);
|
c = 2. * Math.atan(rh / this.akm1);
|
sinc = Math.sin(c);
|
cosc = Math.cos(c);
|
lon = 0.;
|
switch (this.mode) {
|
case this.EQUIT:
|
if (Math.abs(rh) <= Proj4js.common.EPSLN) {
|
lat = 0.;
|
} else {
|
lat = Math.asin(y * sinc / rh);
|
}
|
if (cosc != 0. || x != 0.) lon = Math.atan2(x * sinc, cosc * rh);
|
break;
|
case this.OBLIQ:
|
if (Math.abs(rh) <= Proj4js.common.EPSLN) {
|
lat = this.phi0;
|
} else {
|
lat = Math.asin(cosc * this.sinph0 + y * sinc * this.cosph0 / rh);
|
}
|
c = cosc - this.sinph0 * Math.sin(lat);
|
if (c != 0. || x != 0.) {
|
lon = Math.atan2(x * sinc * this.cosph0, c * rh);
|
}
|
break;
|
case this.N_POLE:
|
y = -y;
|
case this.S_POLE:
|
if (Math.abs(rh) <= Proj4js.common.EPSLN) {
|
lat = this.phi0;
|
} else {
|
lat = Math.asin(this.mode == this.S_POLE ? -cosc : cosc);
|
}
|
lon = (x == 0. && y == 0.) ? 0. : Math.atan2(x, y);
|
break;
|
}
|
p.x = Proj4js.common.adjust_lon(lon + this.long0);
|
p.y = lat;
|
} else {
|
rho = Math.sqrt(x*x + y*y);
|
switch (this.mode) {
|
case this.OBLIQ:
|
case this.EQUIT:
|
tp = 2. * Math.atan2(rho * this.cosX1 , this.akm1);
|
cosphi = Math.cos(tp);
|
sinphi = Math.sin(tp);
|
if( rho == 0.0 ) {
|
phi_l = Math.asin(cosphi * this.sinX1);
|
} else {
|
phi_l = Math.asin(cosphi * this.sinX1 + (y * sinphi * this.cosX1 / rho));
|
}
|
|
tp = Math.tan(.5 * (Proj4js.common.HALF_PI + phi_l));
|
x *= sinphi;
|
y = rho * this.cosX1 * cosphi - y * this.sinX1* sinphi;
|
pi2 = Proj4js.common.HALF_PI;
|
halfe = .5 * this.e;
|
break;
|
case this.N_POLE:
|
y = -y;
|
case this.S_POLE:
|
tp = - rho / this.akm1;
|
phi_l = Proj4js.common.HALF_PI - 2. * Math.atan(tp);
|
pi2 = -Proj4js.common.HALF_PI;
|
halfe = -.5 * this.e;
|
break;
|
}
|
for (i = this.NITER; i--; phi_l = lat) { //check this
|
sinphi = this.e * Math.sin(phi_l);
|
lat = 2. * Math.atan(tp * Math.pow((1.+sinphi)/(1.-sinphi), halfe)) - pi2;
|
if (Math.abs(phi_l - lat) < this.CONV) {
|
if (this.mode == this.S_POLE) lat = -lat;
|
lon = (x == 0. && y == 0.) ? 0. : Math.atan2(x, y);
|
p.x = Proj4js.common.adjust_lon(lon + this.long0);
|
p.y = lat;
|
return p;
|
}
|
}
|
}
|
}
|
};
|
