Archive for the ‘ Sven Gastauer ’ Category

2013 rêve d’un îlot d’humanité


Alles Guddes fir

Nos meilleurs voeux pour


 rêve d’un îlot d’humanité


Alles Guddes fir 2013

Meilleurs voeux pour 2013

Yvette, Romain, Sven, Ben & Nora Gastauer

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Gerrit Rietveld Academie Graduation Show

Le vernissage de l’expo de fin d’année scolaire de la Gerrit Rietveld Academie aura lieu ce mercredi 4 juillet  à Amsterdam

Sven Gastauer : Calibration and Galway (23.03.2012)



We just entered the harbour of Galway, where we will stay over the weekend.

Yesterday evening and this morning, we did calibrate our echosounders (38 kHz and 120 kHz) in the Galway Bay (see figure 2). The calibration was a little bit more difficult then expected as we had to face quite strong currents and winds. Hence, we couldn’t manage to get the sphere to cover the entire beam as the current was just forcing it out of range all the time. This left us with no other option than to wait for better weather conditions, which we expected to occur at around midnight and at 6 in the morning. Luckily the predictions were quite accurate and we did manage to do two good calibrations on our 38 kHz echosounder (main frequency) as well as 1 good and 1 almost good calibration of the 120 kHz echosounder.



What, why and how –

Calibration of echosounders Calibration of acoustic equipment is very important for us, as it gives us an estimate of how accurate the equipment is working (this is important as the sounders may perform differently under varying conditions i.e. salinity, temperature). Without a calibration no quantitative results can be taken out of the acoustic data, e.g. no biomass estimates and species determination using multiple frequencies, further calibrating the equipment allows us to detect errors in the system and to solve those before we start with the ‘real’ survey. Calibration should be done in a sheltered area, close to the area of interest, with a water depth of at least 20 m. To calibrate, we use a copper or tungsten carbide sphere, with a known target strength (echo), attach it to 3 lines, which can be steered from deck, and then the sphere is placed underneath the echsounders, in our case the towed body (metal frame with the acoustic equipment, floating next to the ship, see figure 1). The next step is the real calibration, where we have to move the sphere around in the acoustic beam, trying to get the entire beam covered. Finally if we have covered the beam we can look at the result and look at the strengths of the detections in the entire beam which should be close to the reference values of the sphere. In a next step we can update our beam information with these values, e.g. apply a correction filter to the echo. To finalise the calibration, we do a second run to make sure that the applied correction is performing well and we did not worsen the set up.

Sven Gastauer : new blog

I am back at sea, this time we are heading towards west of Ireland, seeking blue whiting and doing a couple of deep sea trawls. We will have a blog up and running again this year, i.e. you have something to read every day and do not forget to post comments… and Sven Gastauer and Kees Bakker will join the Dutch part of this years blue whiting acoustic survey in spring 2012. 19 March – 13 April 2012 On this site you can follow the Ship Blog: ShipBlog The cruise track covered by the Dutch research vessel Tridens II is given in orange on the map below. It represents the EU part of an internationally coordinated effort to estimate the size of the blue whiting stock west of the British Isles. The area will be surveyed on a systematic, predefined cruise track. During the survey we continuously send out vertical sound waves through the water and collect acoustic backscatter data. We can visualise these data in a so-called ‘echogram’ – essentially a 2-dimensional slice through the water column. Once we have completed the survey of the area, we combine all the echo energy that was reflected by blue whiting and convert it into fish numbers and weight. Yesterday morning we left the port of Scheveningen (Den Haag)at around 11 o’clock with very good weather. Since then we are steaming towards Ireland, with the wind in the back we can go quite fast and we expect to arrive in Galway around lunchtime tomorrow morning. This afternoon we left the channels, so we entered the “real” oceans and experience some first waves, but the weather is still quite good .

The plan is to calibrate our echosounders in the Galway Bay on arrival tomorrow after lunch. Probably we will then step on shore on Friday morning and lay in the harbor for the weekend. The survey itself will start on Monday morning some miles off the coast. At around 7 we should be able to leave the bay with the high tide.


Alles Guddes 2011

Alles Guddes 2011

sortir de l'ombre 2011

sortir de l’ombre 2011

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