A Word About the Technology Behind FUEL GPS
Good morning bloggies,
We are often asked about the accuracy of FUEL GPS, and sometimes with a degree of skepticism, which is understandable, when something new comes along. First of all, FUEL GPS is not your daddy’s GPS receiver, but still has much in common with traditional GPS receivers, of course. The primary difference relates to priority given to the design of FUEL’s measurement unit, the correlator.
As many people know, GPS satellites transmit coded signals to Earth. The civilian signal, referred to as the Coarse Acquisition Code (C/A code), has a “chipping” frequency of just over one mega-Hertz (MHz). One chip is essentially one binary transition within the code structure. When you take the speed of light (about 3.0E8 m/s) and divide it by the chipping frequency, you’ll find that the spatial length of one binary digit is about 300 meters (about 330 yards - the length of a short par 4, for you golfers). So, each of these chips / binary digits are quite long.
The job of the correlator is to align the receiver’s internal copy of the C/A code with that received from the GPS satellite. When the two codes are aligned, and knowing when the current chip was transmitted, and precise location of the satellite, the receiver can compute its antenna-to-satellite distance. The more accurately the codes can be aligned in time, or correlated, the higher the precision of the distance measurement.
The advanced correlator design within FUEL does just this. It matches the codes with a high degree of time / spatial precision. These distance measurements are input into a navigation filter that produces the locations from FUEL. Much work has gone into the design of this filter that combines the GPS distance measurements with other important information, such as satellite orbit information and carrier phase data. The outcome of the filter is a train of accurate positions as FUEL GPS navigates around a track or is used for vehicle performance measurement.
Emphasis on the correlator has some other implications, including processing power, which is at the compromise of power consumption. Though not a highly power-hungry system, don’t expect FUEL to be powered by a few AA batteries for long, like a hand-held GPS! Part of this consequence is the processing power within FUEL GPS. It is required to be high, to ensure that there is sufficient bandwidth to accommodate the 10 Hz and 20 Hz positioning rates, which BTW, are unique and non-interpolated.
When we exhibited at last year’s Performance Racing Industry show in Orlando (we’ll be there this year too!), we had one individual come to us who had worked on military fighter jets. He didn’t believe the claims of our FUEL GPS accuracy, as it rivals the performance achieved by military GPS. However, it’s not a secret that survey-grade GPS systems can achieve between one and two cm (under an inch) accuracy in real-time. This is not without its share of technical challenges, requiring a expensive GPS equipment, dedicated GPS base station, a communications link, and the surrounding system complication. GPS has been used effectively for many years for a multitude of applications including drilling rig positioning, surveying, earth quake prediction, dam deformation monitoring, and others.
What makes FUEL GPS unique is the state of its technology in comparison to other affordable / accessible GPS gear. There simply isn’t a better solution available with its precision, price-point, and ease of use. We challenge you to find one. If you do, perhaps we’ll buy one too!
Brendon
Tag: gps, speed sensor, high accuracy gps, racing, race data logger, racing logger, gps lap timer, lap timer, gps speed sensor, data acquisition