Techniques for point-level speed calculation from GPS traces

I am working with a GPS dataset where GPS speed is not available, only the lat/lon coordinates and timestamp.

Currently, I calculate point-level speed from rate of distance between two consecutive points (distance/delta_time). However, the result usually gave large errors due to the errors in GPS.

Are the other means or techniques to estimate the point-point speed?

EDIT

Currently, I calculate the speed in python using the geopy package, like so:

from geopy.distance import vincenty
A = (Data[i, 0], Data[i, 1])
B = (Data[i + 1, 0], Data[i + 1, 1])
pointSpeed = vincenty(A, B).meters/delta_time[i]