To get an idea on what kind of sampling rate you need, most people sample at a rate higher than needed. At a max speed of 60 km/h which is about 17 m/s so sampling at 10 Hz would show a change in position of at most 1.7 m at max speed which is less than the accuracy of the position the GPS will most likely provide, implying a 10 Hz sampling rate is oversampling for no increase in the quality of your final result.
Reducing the sampling rate will give you some extra room for speeds on SD gard storage rate, extra battery life etc.
Just something to think about,
wade