Quick Survey Time Estimation

Chesapeake Times, Vol 7 | October 2021

There are a handful of tools in SonarWiz, that, together, can help you make quick work of putting together a survey time estimate.

After creating a project in the intended location/zone, create or import a closed polygon feature matching the area to be surveyed. In this example I’ll import a 1.8km x 1.9km rectangle from a shapefile; if no vector representation of the area is available, making a closed polygon feature by hand will do for a quick estimate.

 Right-click the Features node of the Explorer tree and select “Import…” to open the feature import window:

In this case, I’ve chosen a shapefile containing just one rectangle, resulting in a feature that looks like this:

Right-click the new feature in the Explorer tree and select the “Build Survey Lines in Selected Feature…” menu item. This will invoke a tool that will let you fill a polygon with survey lines of a given spacing and orientation:

Here, SonarWiz will fill the area using the efficient survey pattern (see Patrick’s article from the Times, issue four), running approximately east-west lines. I’ve nudged the bearing by a degree to account for the grid convergence angle at this location, to better match the orientation of the lines with the feature they’re filling. Accepting these values produces a set of survey lines like this:

From the Data Acquisition toolbar, launch the survey line manager window:

Click the “Survey Time…” button near the right edge to bring up the survey time estimator:

Here, I’ve chosen a speed of four knots, having determined that there’s sufficient along-track resolution at that speed. Turning time between lines is estimated at 30 seconds. Clicking the “Report…” button at the bottom of the window will write out a CSV file with survey time estimates per line. A little spreadsheet formula work gives us an overall estimate of 377 minutes – around six and a half hours to cover a bit less than four square kilometers.

That’s all there is to it. In just five minutes or so, I’ve got a rough estimate of the time it would take to cover this area, and by repeating the last couple steps, I can do the same for varying speeds. Further, I’ve got a working set of survey lines to use with SonarWiz’s realtime and helm display tools when on the water.

– Jonathan Fleetwood, Engineer