Abstract: A depth measurement system particularly suitable for automatically driving a recorder under varying wireline measurement conditions for repeatedly depth recording measurements from borehole tools produces different measurements at generally the same point on the wireline which would correspond if measurement conditions were ideal, but are subject to non-repeatable variations. Accordingly, these signals are automatically utilized to provide a repeatable signal. In one form, the signals correspond to magnetic marks and to incremental movement of the wireline, the latter produced by mechanically coupled devices subject to slippage, variations in circumference, etc. The incremental signals are counted and compared with the number expected for such intervals, a low count indicating slippage or the like and used to provide an appropriate alarm and/or an automatically slippage corrected signal particularly suitable for driving a recorder.