What is a time window and two-way travel time?

November 25 2021

In a GPR system the time window is defined as the time the receiver antenna (Rx) listens to, and records, echoes from a transmitted electromagnetic pulse. This is also known as the two-way travel time of the GPR signal. In other words, the time window defines the total trace length.

All measurements collected with a GPR system is measured in time, so it is important to understand the concept of the time window and how it affects your data collection. If the time window is too short you may stop listening and recording before the signal has reached the desired target depth. If it is too long the size of the files may be unnecessary large.

The time window is most often expressed in nano seconds (ns) and together with the velocity (m/ns) of the electromagnetic pulse in the investigated media it can provide the operator with a total investigation depth (in meter).

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So, when prolonging the time window in a homogeneous medium the investigation depth increases. But if the medium changes to a slower one (say from dry sand to saturated sand), the investigation depth will decrease (if you are using the same time window settings).

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The time window can also be described as the number of samples per trace.

What is a time window and two-way travel time?

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