With the development of the BeiDou system

the features of mixed constellation have become more obvious with GEO and IGSO satellite orbits

the number of high elevation satellites has obviously increased

and the number of visible satellites has increased among high buildings. Therefore

we propose a new method wherein fewer satellites can also have better positioning a ccuracy with GEO /IGSO satellites. This method is also applicable to urban environment. To prove the effectiveness of this new method

we perform tests under open and urban environments. We also use two modes to verify the new method. The first mode u ses combinations from all BeiDou satellites with several GPS satellites

and the second mode uses combinations from several B eiDou and several GPS satellites. We select fewer satellites of BeiDou and GPS whose position dilution of precision is the smallest and then compare the positioning results with the BeiDou

GPS

and BeiDou /GPS systems under the two environments. Experimental results under the two environments show that the BeiDou system has better positioning performance than the GPS system. Under open environment

both modes of the new method can use fewer satellites to perform better positioning performance than the BeiDou /GPS system. The performance with the second mode is better than that with the first mode. Under urban environment

the features of the GEO and IGSO satellites of the BeiDou system can be maximized. Compared with the GPS system

the BeiDou system has more visible satellites because of the particularity of GEO and IGSO satellite orbits

as well as better positioning p erformance.In the first mode

the positioning error of our method is always less than that of the BeiDou or GPS system and is frequently less than that of the BeiDou /GPS system. In the second mode

the new method has less positioning error and fewer s atellites than the BeiDou /GPS system. Therefore

under urban environment

using fewer satellites can also have better positioning performance with the new method. This study proposes a new method to select fewer satellites. Two modes are used to verify the new method under open and urban environments. The BeiDou system displays better performance than the GPS system under both environments. Considering the full use of GEO and IGSO satellites in the two modes

we can conclude from the experiments that fewer satellites can also have better positioning performance. This research is necessary and effective particularly under urban environment.