GPS positioning faster than 1Hz
All modern GPS receivers will provide you with a position update rate of 5Hz or 10Hz (e.g.MTK3339). However, the speed signal the GPS provides is derived from the satellite signals and not from the position update rate. The speed can alternatively be calculated from one position to the next one (difference of position divided by passed time). If that method is used a higher position update rate is desired because a sudden change of speed will need too long to be visible.

As someone else mentioned the 1PPS has nothing to do with that, it is only a clock reference independent from speed or update rate.