||Global Navigation Satellite Systems have become the fundamental infrastructure to support economic development globally. Hong Kong is establishing its own positioning infrastructure. Recently, based on Hong Kong GNSS reference network developed by the Lands Department, two services have been provided to support meter level DGNSS for mobile users and centimeter level for professionals through the corrections of GNSS systematic errors. However, GNSS does not work well in urban areas, as GNSS signals are blocked by building. The positioning error of hundred meters can occur in the dense city regions due to multipath effect, which restricts the applications of positioning technologies in Hong Kong. This project will develop an integrated solution to solve the multipath problem in Hong Kong. It will integrate multiple sensors, including Micro-electromechanical Systems sensors, WIFI, satellite in view, and multiple GNSS constellations (i.e. GPS, Beidou, GLONASS, and other available satellite navigation systems), together with 3D city model, to significantly reduce multipath effect by using advanced fusion algorithms and multipath modeling. Moreover, this model can be applied in other regions with available 3D city model. This will lead to seamless positioning service in both open area and dense building regions for Hong Kong. The accuracy of the integrated service is expected to be 2 m and 10 m for open and dense building areas respectively.