For detailed mapping of global radiation received at ground the Heliosat method of Ecole Nationale Superieure des Mines de Paris, Sophia-Antipolis (France), is applied. Preliminary results of a validation for Germany are presented. Precision of Heliosat insolation estimates is assessed by comparison of monthly averaged hourly and daily sums and of weekly sums acquired in August 1994 and February 1995 with pyranometric measurements from 4 stations of the German Weather Service (DWD). The predictions RMS error amounts to 7% of the observed August 1994 monthly averaged daily global irradiation of 4285 Wh/m(2) and to 15% of the observed February 1995 monthly averaged daily global irradiation of 1297 Wh/m(2). The error of the estimation of monthly averaged hourly global irradiation is less than 100 Wh/m(2). These values are within the limits of what has been reported hitherto.