The order of the polynomial is chosen such that it best fits the expected function by visual judgment and such that the polynomials for the fusion, Lidar and radar results are similar.
The polynomials are drawn as black lines in Figures 8(a), 8(b), and 8(c).
The standard deviation of the actual values (with the artificially created ground truth taken as mean value) is taken as indicator for their precision (shown in Table 8(d)).
Note that the artificial ground truth adds an error to the analysis,but we considered it adequate enough to be significant.