One of the fairest mechanisms of Electronic Toll Collection (ETC) would be distance-based charging, where vehicles
would pay fees at a pre-specified rate per kilometer throughout the trip. The vehicle positioning system (VPS) based on
GPS (Global Positioning System) has become the main ETC technology worldwide recently. One of the key algorithms
for VPS is how to provide accurate distance calculation data. Therefore, a digital mileage calculating program utilizing
the position information from a commercial GPS receiver to filter out noises should be developed to accumulate the total
distance of a voyage incrementally. Due to environmental climates and built-up in a metropolitan area such as high
buildings, bridges, radio stations, tunnels and traffic subways, signals of GPS satellites are easily susceptible to noises
or even totally blocked. In such cases, the GPS position information loses fidelity. This paper presents a procedural
program, incorporating an algorithmic software filter adaptive to different situations, is an answer to the above problems
and is capable of providing the mileage of a voyage in real-time base with high accuracy compared to a mechanic
mileage meter.
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