Localization is critical for autonomous vehicles, sea transport guidance, air transport guidance, and present day military missions. When the Global Position System (GPS) is denied or spoofed, current navigational devices can become highly inaccurate. For instance, an Inertial Measurement Unit (IMU) heading estimate will drift, accumulate error, and degrade the position over time.
The Sky Polarization Azimuth Sensing System, SkyPASS®, provides an inexpensive method for measuring absolute orientation in a GPS denied environment. The system is passive and well suited for any man or vehicle platform to provide mission critical navigational localization accuracy regardless of GPS accessibility.
SkyPASS® Features and Benefits
- Less than 2 mil heading accuracy
- Calculates absolute heading
- Works even when GPS is denied
- Low SWaP
- Low cost
- No start-up delay
- No set-up or leveling
- Not affected by magnetic disturbances
- Navy Ships
- Autonomous Robots
- Far Target Locator
Far Target Locator
There are four variables that must be defined in order to determine the location of a target on Earth. There is azimuth (or bearing), distance (range), vertical angle (elevation), and self-position (latitude, longitude, and altitude above sea level) to the target. The largest source of Target Location Error (TLE) in existing Far Target Location (FTL) systems is accurately determining azimuth. In most cases, azimuth errors in the guidance of man-portable weapon systems would lead to failure of target acquisition, target destruction, and possibly endanger friendly forces. Currently, available high accuracy (1-4 mil, where mil is a milliradian or 0.56°) azimuth sensors are expensive, bulky, heavy, and power hungry; require up to 4 minutes for set up; and/or have availability issues. Digital magnetic compasses have long been an inexpensive means for azimuth determination, but they are hindered by magnetic interference and offer only marginal accuracy.
The Sky Polarization Azimuth Sensing System (SkyPASS®) is a high accuracy, low SWaP-C solution for determining azimuth within 1-2 mills for any platform requiring accurate heading information including man-portable weapon systems. SkyPASS® is not hindered by many of the operational limitations seen in the current azimuth sensing methodologies. SkyPASS® provides accurate azimuth in real-time, does not require leveling, and can even assist in determining orientation when GPS is unavailable.
How it Works
Sky polarization is an upper atmosphere phenomenon observable from any point on earth or from any aerial platform. In the diagram above, the time of day is shown at the top of each polarization map, the sun is shown as a small, yellow disc, and the center of each plot is the zenith. Using advanced algorithms and optics, SkyPASS® is able to detect and decipher the polarization map of the sky to compute highly accurate heading.
It is important to note that sky polarization sensing is not affected by magnetic disturbances, does not require leveling or field calibration, and can provide an instantaneous answer. When compared to celestial sensing methods, like Sun or Star trackers, SkyPASS® outperforms in that it can operate in a variety of cloud conditions, at solar noon, and around sunrise/sunset. The SkyPASS® sensor can be produced at a much lower cost than competing technologies, thus, enhancing a military capability while reducing overall cost. A celestial method that can operate at sunrise/sunset, at solar noon, and in a variety of cloud conditions, SkyPASS® is the next step forward in orientation sensing. SkyPASS® has been tested as an add on to the Far Target Location (FTL) systems that enable the warfighter to determine target position with a very high degree of accuracy. The system has also been attached to the exterior of aircraft to determine heading accuracy.