How-to Watercolumn Data
This How-to describes how to set up and use the water column data from a Kongsberg EM multibeam echo sounder in Qinsy.
The water column data can be translated into an image of all the acoustic data acquired by the sounder in one ping.
The water column imagery can be viewed online and in processing for additional Quality Control of the echosounder and for determining the shallowest point during wreck detection.
On this page:
Setup
This chapter describes how to set up Qinsy and the multibeam system prior to going online.
Currently only the following Multibeam Systems are supported for water column data:
- Kongsberg
- R2Sonic
- Reson
Other models and manufacturers can be added on request.
Open Database Setup, select Multibeam System, go to the Driver Specific Parameters page and enable the option “Water Column Usage”. (If this option is grayed out it is not supported for the driver configuration.)
For a dual head system this should be done for both multibeam systems.
For more information about the required telegrams and supported systems please refer to: 'How-to Raw Data Usage (XTF / GSF / Snippets / Watercolumn)' and the related Driver Manual of your Multibeam System.
EM3002 Echo sounder
The EM3002 echosounder should output the so-called water column datagrams (type = k) over the network to Qinsy (together with the other datagrams). This is done automatically when the Qinsy EM controller driver is used to control the EM3002.
If however the EM3002 is controlled from SIS or from an old Kongsberg Controller program the ‘k’ datagrams should be enabled in there.
Important
If you are going to use the EM3002 for wreck detection, make sure to select Equidistant or Equiangular beam spacing for the EM3002.
The High Density mode is not supported due to a limitation in the ‘k’ datagram beam data.
Data recorded in that mode can only be viewed but not edited in processing!
Online
Start the Qinsy Controller. Create a new Multibeam Display, select Multibeam System.
The display should now automatically show the water column data in the background. If not check the network datagrams.
Controller
The water column datagrams can be stored optionally in the database but this will require a lot of hard disk space. Per ping per head up to 900 KB can be stored. This figure will depend on water depth but will typically lie between 10KB to 150KB.
In the Controller you can select if the raw water column data will be recorded or not. If data is not recorded you can still use the water column data to view the sonar acoustic signal in the Raw Multibeam Display.
This option can only be accessed when recording is off, so before a line is sailed decide whether it is interesting to store the water column data for that line.
Raw Multibeam Display
The Raw Multibeam Display will normally show an aft view of the raw decoded swath bottom detection points, uncorrected for attitude.
The display can also be used to show the water column imagery. If water column imagery is shown then the swath is shown corrected for roll and mounting angle.
Settings
Refresh rate
Normally the raw multibeam display will update every time a new swath is decoded but when showing the water column data this may lead to an unacceptably high cpu load.
If you witness high cpu load for the display, try reducing the refresh rate.
View Properties, water column data tab
Show Watercolumn Data
Hide or show the water column data image in the back ground.
Intensity
Amplification factor for the image: the lower the intensity the darker the image.
Beam Opening Angle
The individual beams are drawn in the swath like a cone. The dimension of the cone depends on the number of samples and the beam opening angle.
The beam opening angle can either be derived from the values entered in Database Setup for the multibeam system or can be set to Auto.
The cone is then defined in such a way that the image is filled with no overlap to its neighboring beams.
Info
For a dual head EM3002 you will have to open two separate displays: one for port and one for starboard.
It is not possible to show them merged in one display.
Processing with Qimera
There is a document named 'How-to Water Column Sounding Extraction' which describes how soundings can be extracted from Watercolumn data.