A method comprises obtaining data points, each comprised of a time stamp and measurement; dividing the data points into sequences of consecutive data points; limiting the maximum time between consecutive data points in the same sequence; limiting the maximum time between the earliest and latest data points in each sequence; calculating a polynomial of lowest transmission cost for each sequence; limiting the approximation error between the data points in a sequence and the associated polynomial; and transmitting, to a server, data based on the calculated polynomial.