So long as you know the type of rock at the point where the Measurement is made, you can get an idea of what lies beyond the probe, and in all directions. The actual teather may create a bit of noise for a small distance (a few meters at most) in only one direction (above the actual Probe. It is all based on Conductivity of one form and or another. When the composition of the Rock changes, so does the Conductivity, so the Theory goes.
Thus the DH 09 - 49 provided a Two Foe One experience. NOT too uncommon in this Business.
However, it is usually desirable to move from nonmineralized rock to mineralized rock, as that is the typical way in which the Mathematical Algoithms are created to compile and interpret the raw data. But the Data is still good regardless of from which point (rock type - conductiveness) is was obtained. Sight or Radar/sonar are a different beast. The type of probe used here does not seek these types of information. They seek Conductivity of one form or another. Conductivity VS Reflectivity.
Old Joe