Time in GPR has different meanings: Time Window = the maximum recording time shown on the data. This can be used to calculate the depth. Acquisition Time = how long it takes to finish one A-scan measurement with a perfect electronics instrument for pulsed GPR. However, GPR devices are not able to collect one A-scan in a single pass and, to reduce noise, normally an A-scan is measured multiple times, and then results are averaged together. So the Acquisition Time is longer than the Time Window.