@memori.ai/memori-react/src/helpers/venue.ts

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export const EARTH_RADIUS_AT_45_DEGRESS = (6357.0 + 6378.0) / 2.0;
export const DEGREES_TO_RADIANS = Math.PI / 180;

export const getUncertaintyByViewport = (
  bouningBox:
    | [number, number, number, number]
    | [string, string, string, string]
) => {
  // https://nominatim.org/release-docs/develop/api/Output/#boundingbox
  const [minLat, maxLat, minLng, maxLng] =
    typeof bouningBox[0] === 'string'
      ? (bouningBox as string[]).map(parseFloat)
      : (bouningBox as number[]);

  // Convert latitude and longitude to radians
  const phi1 = minLat * DEGREES_TO_RADIANS;
  const lambda1 = minLng * DEGREES_TO_RADIANS;

  const phi2 = maxLat * DEGREES_TO_RADIANS;
  const lambda2 = maxLng * DEGREES_TO_RADIANS;

  // Compute distance using the haversine formula
  // https://en.wikipedia.org/wiki/Haversine_formula
  const angle =
    2.0 *
    Math.asin(
      Math.sqrt(
        Math.sin((phi2 - phi1) / 2.0) * Math.sin((phi2 - phi1) / 2.0) +
          Math.cos(phi1) *
            Math.cos(phi2) *
            Math.sin((lambda2 - lambda1) / 2.0) *
            Math.sin((lambda2 - lambda1) / 2.0)
      )
    );
  return EARTH_RADIUS_AT_45_DEGRESS * angle;
};