The program draws automatically more or less smooth lines passing through the measured data.You can modify the speed lines with the help of the mouse. Move the mouse arrow to the beta line where you want to correct and then press the left button. Two segments of the speedline are now being modified; use the mouse to shift the lines. Release the button to fix the speed line in its new position.

There are several possibilities of crosschecking the speed lines. Click on a tab to get a different view of the map. When you have a big screen then it makes sense to look at four graphics simultaneously while you are working with the speed lines: