/** Mean Earth radius, kilometres, the same unit the satellite positions use. */
export declare const PAINT_EARTH_KM = 6371;
/** The painted texture: equirectangular, north at the first row, longitude −180 at the first column. */
export declare const PAINT_W = 1024;
export declare const PAINT_H = 512;
export interface LonLat {
    lon: number;
    lat: number;
}
/** Earth-central angle, in radians, where a satellite `heightKm` up is at least `elevationDeg` above the horizon (10 when left out). 0 when it never is. */
export declare function coverageAngleRad(heightKm: number, elevationDeg?: number): number;
/** The ground under a satellite. `x, y, z` are what `Satellites.exact` writes (Earth radii, x to the vernal equinox, y north). `ms` turns the Earth under that place. */
export declare function groundUnder(x: number, y: number, z: number, ms: number): LonLat & {
    heightKm: number;
};
/** Points from `a` to `b` along the great circle, about `stepDeg` apart, including both ends. A fast clock stays a continuous line, and a pole or the date line is many short steps. */
export declare function trackSteps(a: LonLat, b: LonLat, stepDeg: number): LonLat[];
/** One segment, or two when the short way from `a` to `b` crosses the date line, so an equirectangular line does not cross the whole map. Longitude is degrees, −180 to 180. */
export declare function splitDateLine(a: LonLat, b: LonLat): [LonLat, LonLat][];
/** Where a longitude and latitude fall on the painted texture, column and row. */
export declare function paintPixel(lon: number, lat: number): {
    x: number;
    y: number;
};