Acoustic vs Optical Televiewer: Which Should You Use?

If you've ever required borehole imaging on a project, you've probably had to choose between an Acoustic Televiewer (ATV) and an Optical Televiewer (OTV), or wondered whether you should be running both. The two tools produce similar looking 360 degree borehole images but rely on fundamentally different methods. This guide explains what each tool does, when to choose one over the other, and the situations where running both is the right call.

How each tool works

Optical Televiewer (OTV)

An OTV is essentially a high-resolution downhole camera that images the borehole wall. As the probe is lowered down the borehole, it captures a continuous unwrapped 360 degree image. The result is a true colour image where you can see bedding, fractures, mineralisation, lithology changes, and any features visible to the naked eye.

Because OTV depends on light, the borehole must be either dry or filled with clean, clear water. Anything cloudy, muddy or turbid and the image will be useless. Services

Acoustic Televiewer (ATV)

An ATV uses a rotating ultrasonic transducer to send a focused acoustic pulse at the borehole wall and measure two things from the returning echo. The travel time (which gives borehole geometry and caliper) and the amplitude (which reflects acoustic impedance, broadly correlated with rock hardness). The output is two unwrapped 360 degree images a

travel-time image and an amplitude image.

Because ATV uses sound, it only works in a fluid filled borehole. Services

When to choose OTV

Choose OTV when visual interpretation matters most and your borehole conditions allow it. Typical scenarios:

• Mineral exploration and core-replacement logging where lithology, vein systems and alteration zones need to be identified.

• Geotechnical investigations in dry boreholes above the water table.

• Boreholes that have been flushed with clean water before logging.

• Any project where you specifically need to distinguish features by colour or texture for example, separating bands of weathering or identifying clay seams.

When to choose ATV

Choose ATV when borehole conditions rule out OTV, or when you need quantitative borehole geometry. Typical scenarios:

• Boreholes filled with drilling mud or turbid water common on tunnel and infrastructure projects where flushing isn't practical.

• Boreholes that will not flush clear.

• Projects where caliper data and accurate borehole geometry are required alongside structural mapping.

• Fracture mapping where the priority is detection and orientation rather than visual character.

  
  

When to run both

On many of our larger projects, particularly tunnel and infrastructure work, we run both tools in the same hole. The two datasets are genuinely complementary:

• OTV gives you visual confirmation of features and lithology.

• ATV confirms structures are real (not artefacts of borehole condition) and provides caliper and amplitude data.

• Discrepancies between the two datasets often reveal something interesting for example, an open fracture visible in ATV travel time but partially infilled and harder to spot on OTV.

If your project involves critical structural decisions tunnel alignment, slope stability, dam foundations, contaminated site characterisation running both is usually best. Having two independent datasets makes interpretation easier and reduces the chance of missing something important.

The short version

Running both tools only adds a relatively small amount of additional time onsite but provides you with a greater understanding of the structural and drilling induced defects.

If you'd like to discuss what's appropriate for an upcoming project, get in touch we log boreholes across Australia with logging vehicles in multiple states. We're happy to talk about your next project. Contact