Steps of a solar radius measurement. Top left: brightness profile with the T_B levels (dashed red lines) of T_qS (top line) and the half value of T_qS (bottom line) used in the HP method. Top right: numerical differentiation of the brightness profile (blue curve), whose minimum and maximum points correspond to the limb coordinates of the equatorial scan (red curve) in the IP method. Bottom left: limb coordinates (white points) extracted from a solar map with a fit (circle or ellipse, solid green line). Bottom right: limb coordinates (white points) extracted from a solar map with the statistical procedure to estimate and (the dashed red and blue lines are the constraints of the equatorial and the polar regions, respectively).