Abstract
The mixture of three normal distributions is proposed as a model for an area that we call a ‘class’ in a region according to the spectral brightness of three different band (pixel) values in remote sensing. The parameters in a mixture of three normal distributions arc estimated by the method of moments for grouped data. Newton-Raphson iteration method is used for estimating the parameters where all parameters are unconstrained. The method of finding suitable starting values for Newton-Raphson iterations is also given. A computer program is developed for this purpose.