tethys-feature-service/node_modules/proj4/lib/projections/geos.js

import hypot from '../common/hypot';

export function init() {
    this.flip_axis = (this.sweep === 'x' ? 1 : 0);
    this.h = Number(this.h);
    this.radius_g_1 = this.h / this.a;

    if (this.radius_g_1 <= 0 || this.radius_g_1 > 1e10) {
        throw new Error();
    }

    this.radius_g = 1.0 + this.radius_g_1;
    this.C = this.radius_g * this.radius_g - 1.0;

    if (this.es !== 0.0) {
        var one_es = 1.0 - this.es;
        var rone_es = 1 / one_es;

        this.radius_p = Math.sqrt(one_es);
        this.radius_p2 = one_es;
        this.radius_p_inv2 = rone_es;

        this.shape = 'ellipse'; // Use as a condition in the forward and inverse functions.
    } else {
        this.radius_p = 1.0;
        this.radius_p2 = 1.0;
        this.radius_p_inv2 = 1.0;

        this.shape = 'sphere';  // Use as a condition in the forward and inverse functions.
    }

    if (!this.title) {
        this.title = "Geostationary Satellite View";
    }
}

function forward(p) {
    var lon = p.x;
    var lat = p.y;
    var tmp, v_x, v_y, v_z;
    lon = lon - this.long0;

    if (this.shape === 'ellipse') {
        lat = Math.atan(this.radius_p2 * Math.tan(lat));
        var r = this.radius_p / hypot(this.radius_p * Math.cos(lat), Math.sin(lat));

        v_x = r * Math.cos(lon) * Math.cos(lat);
        v_y = r * Math.sin(lon) * Math.cos(lat);
        v_z = r * Math.sin(lat);

        if (((this.radius_g - v_x) * v_x - v_y * v_y - v_z * v_z * this.radius_p_inv2) < 0.0) {
            p.x = Number.NaN;
            p.y = Number.NaN;
            return p;
        }

        tmp = this.radius_g - v_x;
        if (this.flip_axis) {
            p.x = this.radius_g_1 * Math.atan(v_y / hypot(v_z, tmp));
            p.y = this.radius_g_1 * Math.atan(v_z / tmp);
        } else {
            p.x = this.radius_g_1 * Math.atan(v_y / tmp);
            p.y = this.radius_g_1 * Math.atan(v_z / hypot(v_y, tmp));
        }
    } else if (this.shape === 'sphere') {
        tmp = Math.cos(lat);
        v_x = Math.cos(lon) * tmp;
        v_y = Math.sin(lon) * tmp;
        v_z = Math.sin(lat);
        tmp = this.radius_g - v_x;

        if (this.flip_axis) {
            p.x = this.radius_g_1 * Math.atan(v_y / hypot(v_z, tmp));
            p.y = this.radius_g_1 * Math.atan(v_z / tmp);
        } else {
            p.x = this.radius_g_1 * Math.atan(v_y / tmp);
            p.y = this.radius_g_1 * Math.atan(v_z / hypot(v_y, tmp));
        }
    }
    p.x = p.x * this.a;
    p.y = p.y * this.a;
    return p;
}

function inverse(p) {
    var v_x = -1.0;
    var v_y = 0.0;
    var v_z = 0.0;
    var a, b, det, k;

    p.x = p.x / this.a;
    p.y = p.y / this.a;

    if (this.shape === 'ellipse') {
        if (this.flip_axis) {
            v_z = Math.tan(p.y / this.radius_g_1);
            v_y = Math.tan(p.x / this.radius_g_1) * hypot(1.0, v_z);
        } else {
            v_y = Math.tan(p.x / this.radius_g_1);
            v_z = Math.tan(p.y / this.radius_g_1) * hypot(1.0, v_y);
        }

        var v_zp = v_z / this.radius_p;
        a = v_y * v_y + v_zp * v_zp + v_x * v_x;
        b = 2 * this.radius_g * v_x;
        det = (b * b) - 4 * a * this.C;

        if (det < 0.0) {
            p.x = Number.NaN;
            p.y = Number.NaN;
            return p;
        }

        k = (-b - Math.sqrt(det)) / (2.0 * a);
        v_x = this.radius_g + k * v_x;
        v_y *= k;
        v_z *= k;

        p.x = Math.atan2(v_y, v_x);
        p.y = Math.atan(v_z * Math.cos(p.x) / v_x);
        p.y = Math.atan(this.radius_p_inv2 * Math.tan(p.y));
    } else if (this.shape === 'sphere') {
        if (this.flip_axis) {
            v_z = Math.tan(p.y / this.radius_g_1);
            v_y = Math.tan(p.x / this.radius_g_1) * Math.sqrt(1.0 + v_z * v_z);
        } else {
            v_y = Math.tan(p.x / this.radius_g_1);
            v_z = Math.tan(p.y / this.radius_g_1) * Math.sqrt(1.0 + v_y * v_y);
        }

        a = v_y * v_y + v_z * v_z + v_x * v_x;
        b = 2 * this.radius_g * v_x;
        det = (b * b) - 4 * a * this.C;
        if (det < 0.0) {
            p.x = Number.NaN;
            p.y = Number.NaN;
            return p;
        }

        k = (-b - Math.sqrt(det)) / (2.0 * a);
        v_x = this.radius_g + k * v_x;
        v_y *= k;
        v_z *= k;

        p.x = Math.atan2(v_y, v_x);
        p.y = Math.atan(v_z * Math.cos(p.x) / v_x);
    }
    p.x = p.x + this.long0;
    return p;
}

export var names = ["Geostationary Satellite View", "Geostationary_Satellite", "geos"];
export default {
    init: init,
    forward: forward,
    inverse: inverse,
    names: names,
};