vgridjs/dist/maidenhead.js

Vgrid DGGS JS

// dggs/maidenhead.ts
var MAIDENHEAD_FIELD = "ABCDEFGHIJKLMNOPQRSTUVWX";
var MAIDENHEAD_SQUARE = "0123456789ABCDEFGHIJKLMNOPQRSTUVWX";
var MAIDENHEAD_SUBSQUARE = "abcdefghijklmnopqrstuvwx";
var MaidenheadException = class extends Error {
  constructor(message) {
    super(message);
    this.name = "MaidenheadException";
  }
};
function encode(lat, lon, precision = 2) {
  if (lat < -90 || lat > 90) {
    throw new MaidenheadException("Latitude must be between -90 and 90 degrees");
  }
  if (lon < -180 || lon > 180) {
    throw new MaidenheadException("Longitude must be between -180 and 180 degrees");
  }
  if (precision < 1 || precision > 3) {
    throw new MaidenheadException("Precision must be between 1 and 3");
  }
  lon = (lon + 180) % 360;
  lat = (lat + 90) % 180;
  let locator = "";
  const fieldLon = Math.floor(lon / 20);
  const fieldLat = Math.floor(lat / 10);
  locator += MAIDENHEAD_FIELD[fieldLon];
  locator += MAIDENHEAD_FIELD[fieldLat];
  if (precision >= 2) {
    const squareLon = Math.floor(lon % 20 / 2);
    const squareLat = Math.floor(lat % 10 / 1);
    locator += MAIDENHEAD_SQUARE[squareLon];
    locator += MAIDENHEAD_SQUARE[squareLat];
    if (precision >= 3) {
      const subsquareLon = Math.floor(lon % 2 * 12);
      const subsquareLat = Math.floor(lat % 1 * 24);
      locator += MAIDENHEAD_SUBSQUARE[subsquareLon];
      locator += MAIDENHEAD_SUBSQUARE[subsquareLat];
    }
  }
  return locator;
}
function decode(locator) {
  if (!locator) {
    throw new MaidenheadException("Empty locator string");
  }
  locator = locator.toUpperCase();
  const len = locator.length;
  if (len < 2 || len > 6 || len % 2 !== 0) {
    throw new MaidenheadException("Invalid locator length");
  }
  const fieldLon = MAIDENHEAD_FIELD.indexOf(locator[0]);
  const fieldLat = MAIDENHEAD_FIELD.indexOf(locator[1]);
  if (fieldLon === -1 || fieldLat === -1) {
    throw new MaidenheadException("Invalid field characters");
  }
  let lon = fieldLon * 20 - 180;
  let lat = fieldLat * 10 - 90;
  if (len >= 4) {
    const squareLon = MAIDENHEAD_SQUARE.indexOf(locator[2]);
    const squareLat = MAIDENHEAD_SQUARE.indexOf(locator[3]);
    if (squareLon === -1 || squareLat === -1) {
      throw new MaidenheadException("Invalid square characters");
    }
    lon += squareLon * 2;
    lat += squareLat * 1;
    if (len >= 6) {
      const subsquareLon = MAIDENHEAD_SUBSQUARE.indexOf(locator[4].toLowerCase());
      const subsquareLat = MAIDENHEAD_SUBSQUARE.indexOf(locator[5].toLowerCase());
      if (subsquareLon === -1 || subsquareLat === -1) {
        throw new MaidenheadException("Invalid subsquare characters");
      }
      lon += subsquareLon / 12;
      lat += subsquareLat / 24;
    }
  }
  return [lat, lon];
}
function maidenheadCell(maidenheadId) {
  const [centerLat, centerLon] = decode(maidenheadId);
  const precision = Math.floor(maidenheadId.length / 2);
  let gridSize;
  switch (precision) {
    case 1:
      gridSize = 10;
      break;
    case 2:
      gridSize = 1;
      break;
    case 3:
      gridSize = 1 / 24;
      break;
    default:
      throw new MaidenheadException(`Invalid precision: ${precision}`);
  }
  const minLon = Math.floor(centerLon / gridSize) * gridSize;
  const maxLon = minLon + gridSize;
  const minLat = Math.floor(centerLat / gridSize) * gridSize;
  const maxLat = minLat + gridSize;
  return [centerLat, centerLon, minLat, minLon, maxLat, maxLon, precision];
}

export { MaidenheadException, decode, encode, maidenheadCell };
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