The second method requires little or no correction for sample skew and is immune to DC offset problems. The sample rate is derived by dividing down a reference clock operating at 4 times the carrier frequency. The ADC can operate at up to 2Mhz but the sample rate limit will typically be determined by the carrier frequency and the quadrature sampling method chosen. Each channel has its own TVG values. The number of TVG values may be increased to as many as 32K if needed.
Color coding is based on depth but backscatter amplitude is also available.
No averaging is used either along track or across the track. Range resolution is approximately 2.5cm and the along track beamwidth is 1.3 degrees. The red colour extends up to 0m depth and shows the shoreline of the arm. Photograph of the canoe and experimental setup used to obtain the 3D sidescan image.