Speed and Efficient Survey Pattern

Chesapeake Times, Vol 4 | January 2021

The support team at CTI wants you to succeed on your surveyor’s New Year’s resolution, to record higher resolution data using less track lines! Unlike canceling your new gym membership in February, these tips can be helpful long into 2021.

The first item to take into consideration to improve the resolution of your sidescan data is to slow down when you are recording. For the across track resolution, SonarWiz will always down sample your data to one of three options (1024, 2048, or 4096) so it doesn’t matter how many samples your sidescan actually collected.

You can determine your sample spacing by dividing your slant range by the samples per channel. For example, a 100m slant range divided by 1024 samples per channel would result in 9cm spacing. Determine what required resolution your clients desire as each option (1024, 2048, or 4096) will increase the processing time x2

The important thing to remember is that the resolution of your sidescan lines is more consequently set by your speed over water. You can record the highest density possible in the across track resolution but if you are surveying at 8 knots you are going to have 30cm between pings.

Now that we are running slower speeds, we need to limit the number of track lines. SonarWiz has a built in Efficient Survey Pattern that reduces the time required to cover the same area by over 40% by using the Efficient Survey Pattern formula, which can be found by simply calculating the interline distance required base on the sonar range, maximum planned altitude, and the overlap (helmsman’s accuracy) and enter that number in the Spacing Between Lines fields.

For example, Minor Distance = 75m – (10m + 10m) = 55m Major Distance = 2 x 75m – 10m = 140m will result in this survey pattern:
– Patrick Zynda, Support Engineer