Altitude determination with method 4: time evolution of three features F_i on the cloud. The F1 emergence position is shown as the white plus sign (+) at 20:16 UT (top left). The F2 and F3 emergence positions are shown as the white plus signs at 20:40 UT (top, second image from the left). The white crosses (x) on all observations indicate the emerging positions of the features reported on the observation times (taking into account the eastward rotation of the planet). Finally, the pink plus signs from 20:51 UT to 22:36 UT correspond to the measures of the respective features of the eastern cloud front, closest to and at the same latitude as the emerging position.