asymptotically reaches a new direction. The interpretation of the parameters $A$ and $C$ is as follows.

-   $A$ is the starting point of the warp. It has dimensions of length.

-   $C$ is the (nondimensional) value of the asymptotic slope.

Throughout the rest of the paper, we refer to parameters A and C as those obtained by fitting the experimental points to Eq. 5. These values are shown in Table 3 for the different bands. In addition, we use the angles $\alpha$ and $\beta$, which are most widely used to represent the warp amplitude (Sánchez-Saavedra et al. 2003) Here, $\alpha$ is the angle between the line connecting the galaxy’s centre and the outermost detected point, and the disc’s major axis, while $\beta$ is the angle between the disc’s major axis and the line from the outermost detected point to the point where the warp starts ($A$): see Fig. \[dibu\].

We obtained the same result for the warp parameter $\omega$, whether it was calculated starting from the galaxy centre or from the starting point of the warp, $A$. This confirms that it is not critical to have a precise estimate of the position of the galaxy centre because of the radial 