Positioning is one of the key functional components of intelligent transportation systems (ITS) with communication and computing. Road transport and Location Based Services will make use of GNSS for positioning purpose and both road and LBS are the main application domains of GNSS. This article focuses on urban applications. The rover is moving in streets where buildings around make urban trenches. The so called Urban Trench model is used to correct non-line-of- sight satellites. The principle is first presented. Then several modalities of applying this principle are addressed, in particular the a priori road lane map-matching of the rover position estimate. Last, experimental data are processed with this principle and its various applications, results are shown and analysed, so that first conclusions are drawn and research perspectives designed.