Our curve algorithm is such that you can connect a straight line between each point and it will reflect the actual data at each second. What this means is that in the case of GPS data you need to divide the distance (or speed) difference between two GPS points by the time between them to get the value you increment every second.
Speed @ 10:00:00am 60 mph
Speed @ 10:00:02am 64 mph
This means that the speed at 10:00:01 was 62 mph ((64 - 60)/ 2)