d3-jsnext/src/geo/conic-equidistant.js

d3, but futuristic

import { d3_geo_conic } from './conic';
import { d3_sgn, ε } from '../math/trigonometry';
import { d3_geo_equirectangular } from './equirectangular';
import { abs } from '../math/abs';
import { d3$geo } from './geo';

var d3$geo$conicEquidistant;

function d3_geo_conicEquidistant(φ0, φ1) {
  var cosφ0 = Math.cos(φ0),
      n = φ0 === φ1 ? Math.sin(φ0) : (cosφ0 - Math.cos(φ1)) / (φ1 - φ0),
      G = cosφ0 / n + φ0;

  if (abs(n) < ε) return d3_geo_equirectangular;

  function forward(λ, φ) {
    var ρ = G - φ;
    return [
      ρ * Math.sin(n * λ),
      G - ρ * Math.cos(n * λ)
    ];
  }

  forward.invert = function(x, y) {
    var ρ0_y = G - y;
    return [
      Math.atan2(x, ρ0_y) / n,
      G - d3_sgn(n) * Math.sqrt(x * x + ρ0_y * ρ0_y)
    ];
  };

  return forward;
}

(d3$geo$conicEquidistant = function() {
  return d3_geo_conic(d3_geo_conicEquidistant);
}).raw = d3_geo_conicEquidistant;

export { d3$geo$conicEquidistant, d3_geo_conicEquidistant };