A method to measure the shower transverse profile is described. Calibration data from the lead glass spectrometer GAMS collected with a wide electron beam without any additional coordinate detector are used. The method may be used for the measurements in both cellular- and projective-type spectrometers. A 10 GeV electron shower profile has been measured in the GAMS spectrometer without optical grease between the lead glass radiators and photomultipliers. The shower profile is parametrized as an analytical function. An estimate of the position accuracy is obtained.