During a course of elliptical motion the direction of the body keeps changing however its magnitude may or may not remain constant.
During a curve path motion the velocity of the object is directed in a tangential direction to the curve.
During the motion on a curved path if the magnitude of a body remains constant then the body is said to have a constant speed which is a scalar quantity. Scalar quantities do not have direction.
Uncertainty means that your result may be very random, so you can't trust the first or second or so observation, making several samples critical for accuracy. <span />
