function meridian(lon, lat1, lat2, projection, squaredTolerance) {
  const epsg4326Projection = getProjection('EPSG:4326');
  return line(
    /**
     * @param {number} frac Fraction.
     * @return {import("../../coordinate.js").Coordinate} Coordinate.
     */
    function (frac) {
      return [lon, lat1 + (lat2 - lat1) * frac];
    },
    getTransform(epsg4326Projection, projection),
    squaredTolerance,
  );
}
Generate a meridian (line at constant longitude).
@param {number} lon Longitude.
@param {number} lat1 Latitude 1.
@param {number} lat2 Latitude 2.
@param {import("../../proj/Projection.js").default} projection Projection.
@param {number} squaredTolerance Squared tolerance.
@return {Array<number>} Flat coordinates.