Design considerations for positioning systems in urban environments

Ranging signals in the urban environment suffer from significant attenuation and additive errors caused by reflections. Special design considerations for ranging-based positioning systems that operate in the Urban Canyon are presented. The tradeoff between acquisition sensitivity and acquisition time is presented. The integrity of the measurements is improved by verifying that the signals exhibit the characteristics of the signal structure. The concept of self-aiding using ranging or position fix information to acquire further signals is discussed. Measurement and position fix integrity schemes are discussed which either reject the lower quality measurements due to reflections when possible, or properly adopt them when no other redundant information is present.