Logging method and apparatus using a pad to measure density

A method of determining a physical parameter of geological formations having a borehole passing therethrough by using a sonde lowered down the borehole at the end of a cable and including a source of gamma radiation, a very near detector, a near detector, and a far detector, the method being characterized in that: for each energy window, a model is created characteristic of the response of each detector; a "low resolution" value of the looked-for parameter is determined which, when applied to the model, gives rise to a theoretical measurement that is substantially equal to the "low resolution" real measurement obtained by combining the measurements from all three detectors; the measurements from the two detectors nearest the source are combined to constitute a "high resolution" real measurement; and a "high resolution" value of the parameter is determined which, when applied to the model, gives rise to a theoretical value that is substantially equal to the "high resolution" real measurement, the determination being performed on the basis of the "high resolution" real measurement and of the "low resolution" value of the parameter.