  There are many practical applications based on the Least Square Error (LSE)
approximation. It is based on a square error minimization 'on a vertical' axis.
The LSE method is simple and easy also for analytical purposes. However, if
data span is large over several magnitudes or non-linear LSE is used, severe
numerical instability can be expected. The presented contribution describes a
simple method for large span of data LSE computation. It is especially
convenient if large span of data are to be processed, when the 'standard'
pseudoinverse matrix is ill conditioned. It is actually based on a LSE solution
using orthogonal basis vectors instead of orthonormal basis vectors. The
presented approach has been used for a linear regression as well as for
approximation using radial basis functions.
