gcoord/src/crs/BD09MC.ts

geographic coordinate library

import { Position } from '../geojson';

const { abs } = Math;

const MCBAND = [12890594.86, 8362377.87, 5591021, 3481989.83, 1678043.12, 0];
const LLBAND = [75, 60, 45, 30, 15, 0];
const MC2LL = [
  [
    1.410526172116255e-8, 0.00000898305509648872, -1.9939833816331,
    200.9824383106796, -187.2403703815547, 91.6087516669843, -23.38765649603339,
    2.57121317296198, -0.03801003308653, 17337981.2,
  ],
  [
    -7.435856389565537e-9, 0.000008983055097726239, -0.78625201886289,
    96.32687599759846, -1.85204757529826, -59.36935905485877, 47.40033549296737,
    -16.50741931063887, 2.28786674699375, 10260144.86,
  ],
  [
    -3.030883460898826e-8, 0.00000898305509983578, 0.30071316287616,
    59.74293618442277, 7.357984074871, -25.38371002664745, 13.45380521110908,
    -3.29883767235584, 0.32710905363475, 6856817.37,
  ],
  [
    -1.981981304930552e-8, 0.000008983055099779535, 0.03278182852591,
    40.31678527705744, 0.65659298677277, -4.44255534477492, 0.85341911805263,
    0.12923347998204, -0.04625736007561, 4482777.06,
  ],
  [
    3.09191371068437e-9, 0.000008983055096812155, 0.00006995724062,
    23.10934304144901, -0.00023663490511, -0.6321817810242, -0.00663494467273,
    0.03430082397953, -0.00466043876332, 2555164.4,
  ],
  [
    2.890871144776878e-9, 0.000008983055095805407, -3.068298e-8,
    7.47137025468032, -0.00000353937994, -0.02145144861037, -0.00001234426596,
    0.00010322952773, -0.00000323890364, 826088.5,
  ],
];
const LL2MC = [
  [
    -0.0015702102444, 111320.7020616939, 1704480524535203, -10338987376042340,
    26112667856603880, -35149669176653700, 26595700718403920,
    -10725012454188240, 1800819912950474, 82.5,
  ],
  [
    0.0008277824516172526, 111320.7020463578, 647795574.6671607,
    -4082003173.641316, 10774905663.51142, -15171875531.51559,
    12053065338.62167, -5124939663.577472, 913311935.9512032, 67.5,
  ],
  [
    0.00337398766765, 111320.7020202162, 4481351.045890365, -23393751.19931662,
    79682215.47186455, -115964993.2797253, 97236711.15602145,
    -43661946.33752821, 8477230.501135234, 52.5,
  ],
  [
    0.00220636496208, 111320.7020209128, 51751.86112841131, 3796837.749470245,
    992013.7397791013, -1221952.21711287, 1340652.697009075, -620943.6990984312,
    144416.9293806241, 37.5,
  ],
  [
    -0.0003441963504368392, 111320.7020576856, 278.2353980772752,
    2485758.690035394, 6070.750963243378, 54821.18345352118, 9540.606633304236,
    -2710.55326746645, 1405.483844121726, 22.5,
  ],
  [
    -0.0003218135878613132, 111320.7020701615, 0.00369383431289,
    823725.6402795718, 0.46104986909093, 2351.343141331292, 1.58060784298199,
    8.77738589078284, 0.37238884252424, 7.45,
  ],
];

function transform(x: number, y: number, factors: number[]): Position {
  const cc = abs(y) / factors[9];

  let xt = factors[0] + factors[1] * abs(x);
  let yt =
    factors[2] +
    factors[3] * cc +
    factors[4] * cc ** 2 +
    factors[5] * cc ** 3 +
    factors[6] * cc ** 4 +
    factors[7] * cc ** 5 +
    factors[8] * cc ** 6;

  xt *= x < 0 ? -1 : 1;
  yt *= y < 0 ? -1 : 1;
  return [xt, yt];
}

export function BD09toBD09MC(coord: Position): Position {
  const [lng, lat] = coord;
  let factors: number[] = [];
  for (let i = 0; i < LLBAND.length; i++) {
    if (abs(lat) > LLBAND[i]) {
      factors = LL2MC[i];
      break;
    }
  }
  return transform(lng, lat, factors);
}

export function BD09MCtoBD09(coord: Position): Position {
  const [x, y] = coord;
  let factors: number[] = [];
  for (let i = 0; i < MCBAND.length; i++) {
    if (abs(y) >= MCBAND[i]) {
      factors = MC2LL[i];
      break;
    }
  }
  return transform(x, y, factors);
}