/**
 * Converts GPS time to Unix time (seconds since Jan 1, 1970)
 * @param {number} gpsTime - GPS time in seconds since Jan 6, 1980 (can be negative for times before the GPS epoch)
 * @returns {number} Unix time in seconds
 * @throws {Error} If gpsTime is not a valid number
 */
export declare function gpsToUnix(gpsTime: number): number;
/**
 * Converts Unix time to GPS time (seconds since Jan 6, 1980)
 * @param {number} unixTime - Unix time in seconds since Jan 1, 1970
 * @returns {number} GPS time in seconds (can be negative for times before the GPS epoch)
 * @throws {Error} If unixTime is not a valid number
 */
export declare function unixToGps(unixTime: number): number;