Method for measuring the sagging of a glass panel

A method for measuring the sagging of a glass panel in the process of bending the glass panel on a ring mould, said method comprising:

• establishing a reference plane stationary or positionally fixed with respect to the ring mould;
• measuring the sagging at a glass panel's measuring point;
• and
• applying the measurement data to control progress of the bending process;
• wherein measuring the sapping at the glass panel's measuring point includes:
• using a distance gauge, including a transmitter and a receiver for laser pulses, for measuring a distance between the reference plane and the distance gauge by determining the transmission time of a laser pulse from transmitter to receiver, using a distance gauge for measuring a distance between the glass panels measuring point and the distance gauge by determining the transmission time of the laser pulse from transmitter to receiver, and determining the glass panel's sagging by comparing the distance between the reference plane and the distance gauge to the distance between the glass panel's measuring point and the distance gauge.