The focus of this research is to develop an effective strategy to improve the reliability of the PPP ambiguity resolved user solution. Traditionally, PPP users have been expected to choose between either robust satellite orbit and clock products, which are a combination from multiple analysis centres or select solutions from individual analysis centre that provide PPP-AR products. To address the limitation whereby users were expected to choose between either a robust solution or higher accuracy solution, the following specific objectives are defined: 1. Implementation of ambiguity resolution of the carrier-phase observable; 2. Re-design of the traditional PPP-AR model to an uncombined representation; 3. Examination of the interoperability of multiple PPP-AR products; 4. Development of a combination process for the PPP-AR products; and 5. Re-examination the role of PPP ambiguity resolution.