BD09MC.ts

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 (y >= MCBAND[i]) {
      factors = MC2LL[i];
      break;
    }
  }
  return transform(x, y, factors);
}