The profile points close to the top of the drop present larger error bars due to the density fluctuations in that region (Fig. ), hence, we discard some of those profile points with the criterion of using only data with less than 10 % of relative error. For the remaining data, we use the algorithm presented in Thomas and Chan 30 based on the Landau method to obtain the radius R and centre (x c , z c ) of the circle arc.