GPS velocity measurement researches show that using GPS
Doppler date can provide greater accuracy than indirect
measurement, which is based on positioning data that results
in some errors [8][9] . However, achieving the accuracy of
GPS Doppler speed estimation depends on the number of
available satellites [8]. A study conducted by [5] shows that
the relationship between speed error and the number of
satellites used in speed measurement is inverse. Therefore, it is
important to consider the number of satellites before