Dataset: Simrad acoustic data from RVIB Nathaniel B. Palmer cruise NBP0204 in the Southern Ocean in 2002 (SOGLOBEC project; Southern Ocean Krill project)

Information file for processing and plotting simrad files

The original telegrams from the simrad EK500 for 38, 120, 200 kHz transducers are transmitted to RVDAS via RS232 at 115kb and logged daily with a new file started at 0000 GMT (2000 h local). To process the raw simrad output, the perl script simandmwaythen.pl (written by Karen Fisher) picks up the day.dat file, which must be set by the user, and loads and outputs a series of files for each frequency and time. The matlab m file, simthenplotter_2.m, picks up the output from the perl script, plots and then saves mat files. The m file called plotsimrad.m asks you for the matlab filename and plots the output.

All the matlab files for each day of NBP0204 are available in gz zipped format. All the user needs to do is to unzip the mat file of choice, and run plotsimrad.m. You do not need to go back to the raw data if you just wish to plot data for a particular day or time window. The data in the *.mat files are corrected for the offset produced by the noise margin setting on the simrad and calibrated by cross correlation with data from biomaperII when it was in the water at the same time. This is not a true calibration since the accuracy is unknown, but it probably gives correct backscatter intensity within a few db. The range is -100 to -40 and color scaled (thanks to Gareth Lawson) in the plots just as in the output from biomaperII.

plotsimrad.m allows you to select the times within a given day to plot so you can "zoom in" on specific activites such as CTD or MOCNESS casts. The perl script is made available in case the user wishes to go back to the raw data and re-process for some reason. There is also have a script to cross plot backscatter intensity against temperature gradient data from the CTD and CMIPS during each cast. Contact Scott Gallager if you are interested.

Note about downloading the above program files:
When you click on the above links, the perl script and the matlab files may be output to your browser window. To download them, use 'save as' at your browser's file menu. You can avoid the screen output and download directly by first holding the 'shift' key and then clicking on the link.

Other helpful files:
cmap.m
initialize_simradplot.m

16 sept 2002
Scott Gallager
sgallager@whoi.edu