Examining quality of DGPS-derived positioning data in urban road networks

The differential global positioning system (DGPS) has been and will be used in several large-scale intelligent transportation systems projects in Singapore. This paper examines the availability and reliability of DGPS signal data in all the expressways, and two selected arterials, one bounded by tall residential apartment blocks and another parallel to an elevated mass rapid transit viaduct. The signal availability is measured by coverage, while the reliability is quantified by horizontal dilution of precision (HDOP). The transverse positioning errors are within sub-lane width accuracy on at least 94% of the expressways, and 95% of the arterials. The relationship between HDOP and critical angle for satellite view is also modeled.