1 and t 2 that is the corrected phase shift for t 3 will be thus when these corrected measurements are generated it is not necessary to add a fourth transmitter to obtain the benefits of borehole compensation including correction for electronics errors and correction for borehole rugosity this technique reduces the complexity and cost of adding additional depths of investigation to the logging tool while retaining the advantages of borehole compensation significant further advantage is obtained for the situation when t 3 is placed above t 1 as shown in fig3 processing will be the same as just described in this case the tool length must only be increased by approximately the distance between t 1 and t 3 in a conventionally borehole compensated long array the tool length would have to be increased by twice such distance it will be understood that further transmitters can be added consistent with the principles set forth referring to fig4 a and 4b there is shown a flow diagram of a routine for controlling the processor 270 in accordance with an embodiment of the invention for obtaining borehole compensated resistivity from attenuation and borehole compensated resistivity from phase shift for the spacing of transmitters t 1 t 2 and also for the spacing of transmitter t 3 the block 410 represents initializing of a transmitter index to the first transmitter t 1 the transmitter is activated and the relative phase shift and attenuation are measured and stored as represented by the block 412 inquiry is then made decision block 415 as to whether the last transmitter index has been reached if not the transmitter index is incremented block 417 block 412 is re entered and the.