In this paper, the effective uses of Gerschgorin radii of the similar trans
formed covariance matrix for source number estimation are introduced. A heu
ristic approach is used for developing the detection criteria. The heuristi
c approach applying the visual Gerschgorin disk method (VGD), developed fro
m the projection concept, overcomes the problems in cases of small data sam
ples, an unknown noise model, and data dependency Furthermore, Gerschgorin
disks can be formed into two distinct, non-overlapping collections; one for
signals and the other for noises. The number of sources can be visually de
termined qv counting the number of Gerschgorin disks for signals. The propo
sed method is based on the sample correlation coefficient to normalize the
signal Gerschgorin radii for source number detection. The performance of VG
D shows improved detection capabilities over Gerschgorin Disk Estimator (GD
E) in Gaussian white noise process and was used successfully in measured ex
perimental data.