Function mercatorZfromAltitude

mercatorZfromAltitude(
    altitude: number,
    lat: number,
    circumference?: number,
): number
Convert altitude to mercator projection Z-Value
Parameters
- altitude: number
  in meters
- lat: number
  in degrees
- circumference: number = EARTH_CIRCUMFERENCE
  the circumference of the planet. Defaults to Earth
Returns number
the Z-Value