Discussion on positioning precision improvement plans of twins-satellite navigation system in low latitude area

The positioning performance of Twins-Satellites Navigation System (TSNS) of China is bad in low latitude areas. The four improvement plans based with the navigation information from TSNS satellites, Airborne Pseudolite (APL) or altimeter are discussed. All plans adopt point positioning with code pseudo-range algorithm and evaluate the positioning performance with Geometric Dilution of Precision (GDOP). GDOP changing character could be concluded in theory easily with two methods: 1) analyzing the key elements of predigested Positioning Error Transfer Coefficient Matrix (PETCM), 2) comparing the cubage of tetrahedron constructed by the unit vector along altitude direction and the unit vectors from the user to TSNS satellites and APL. The simulations results show that the plan with APL could improve positioning precision to hundreds of meters except some region where the latitudes of user and APL are close to each other. The plans with APL have good application potential to aiding TSNS in low latitude area.