Cutting Through The Fog With FOG Makes GPS Tracking Better
One of the “dirty little secrets” of GPS navigation and GPS tracking that the manufacturers and dealers rarely spend much time talking about is “the other 5%”. What’s the “other 5%” you may ask? Simple. Look at any official specifications of the GPS and you’ll see that they are carefully specified to deliver some aspect of performance 95% of the time. The other 5% is undefined. It will never be defined, honestly. There are many factors which make that 5% “window” necessary and until the laws of physics get redefined it will stay that way.
One of the chief reasons you will never get much closer to 100% availability or accuracy is the issue of your GPS receiver losing visibility of the sky … being unable to “see” the group of satellites (4 or more) that it has been receiving data from to complete its geographic positioning solution or “fix”. Sometimes this gap in reception is caused by the “urban canyon” (see here and here for some Urban Canyon background) effect. Other times there may be actual physical obstruction such as parking the vehicle in an underground garage. It takes time for GPS to once again acquire enough “good” satellites and recomputed its position.
One technique that can minimize the problems when GPS signals aren’t satisfactory if some form of inertial or dead reckoning navigation built into the units to act as an adjunct to the GPS computed position. A primary part of such a system is something to tell the “box” where north is. Even when GPS is operating nominally there is no true north calculation … GPS give a close approximation of the vehicles track over the ground after two or more fixes are made … but the GPS algorithm really can’t determine direction when standing still.
Inertial systems and digital compasses have long been available, but at high cost. KVH, a company who started out providing systems for receiving TV signals from satellites have taken “north finding” to a new level with their FOG … Fiber Optic Gyro … offerings. A laser is sent through a loop of fiber optic glass and as the loop is moved by the movement of either the vehicle or the Earth the laser beam will appear to move … and a positive direction can be calculated by using the apparent movement of the beam. No moving parts, highly accurate, unaffected by magnetic fields or any sort of electrical interference this is a great step forward.
KVH Industries, Inc. has been awarded a $730,000 Phase II Small Business Innovative Research grant by the U.S. Department of Defense to pursue the development of a fiber optic gyro (FOG)-based northfinding module potentially much smaller and lighter than systems currently available. Expanding on technology used in KVH’s TG-6000 inertial measurement unit and intended as an easy tool to precisely determine azimuth, the proposed system is intended to be a high- performance, affordable product. KVH’s proposed northfinding module aims to bring the benefits of more expensive, heavier high-end inertial systems to customers and applications that were not able to benefit from the technology in the past, such as man-portable mortars. read more about north finding technology and FOG here.
I only hope that GPS manufacturers are quick to see the advantages and will start selling systems that can do better during that troublesome 5% of the time.