Sketch of observation of extraplanar gas in galaxy seen at intermediate inclination. The typical line profile (along the kinematic major axis of the galaxy) will be composed by a nearly Gaussian part coming from the thin disc with overlaid a tail at low rotation velocity produced by the lagging EPG layer. The width of the disc emission is roughly symmetrical, produced by gas turbulence and well fitted by a Gaussian function (blue solid line). The EPG separation is achieved by masking a portion of the profile with substantial contribution from this Gaussian function (“internal mask” region).