<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0
Transitional//EN">Dr. Helge Balk
DEPARTMENT OF PHYSICS
PB 1048 Blindern 0316
fax: +47 22 85 64 22 phone
+47 22856489 mobile +47 97772401 
- FYS3220
H2012 Linear circuit theory
- FYS3180
H2012 Eksperimentelle metoder i fysikk, forelesning av Balk
- Artificial_Lake_Simulator
- Sonar4
and Sonar5 post processing tools
- Hydroacoustiske
målemetoder 10 stp Master kurs
- Laksetelling i Mandalselva
- Talk
at the 33rd scand. Symp.on phys. Acoust. “Detection of fish of in data from DIDSON multibeam
sonar”
- AQUA_PNRF
- Multi frequency study at Cornell
29..31 Aug 2006
- Multi
frequency study in Finland 11..13 Oct 2005
- Research
- Publications, Proceedings and reports
- Exchange files
- My favourite echogram! (Jumping salmon recorded in river Tana summer 1999)
Misc
- Research vessel http://biologi.uio.no/fartoy/braarud.html
- Department of physics : www.fys.uio.no
- Maps of Blindern : http://www.uio.no/om_uio/kart/gaustadblindernnr.html
- Maps of UiO and
- Maps of
- Train information : www.nsb.no/
- Subway information in
- Department of Plankton and Fish Ecology: http://www.hbu.cas.cz/depart.htm
-------
Private
- Hidra
- Horse-riding
- Demmekilen Vel
To day there is an increased interest in shallow water fish-stock assessment and improved monitoring techniques are essential. Hydro-acoustic methods based on single beam, split beam, multi-beam and multi-frequency sonar seems promising. We are focusing on side-looking split-beam sonar. With the correct opening angle, one or a few horizontally mounted transducers can cover major part of a river cross-section. Horizontal beaming from a boat increases the sample volume from the upper part of the water column relative to down-looking applications.
There are, however, many pitfalls and problems connected to side-looking echo sounders in shallow water. High ping-to-ping and sample-to-sample intensity and phase variation in the echo signal from fish are one problem that makes detection difficult. Separating fish echoes from debris, bottom reflection and from erroneous echo detections of peaks in the background reverberation level are also difficult. Great care has to be taken with regard to selecting the site and to setting up the echo sounder’s recording parameters. Still the resulting sonar data might be difficult and tedious to analyse. Automatic methods do not work when the signal to noise ratio becomes poor. The probability of detecting a fish by manual analysis becomes low.
Our research focuses on the understanding of the behaviour of sound in shallow water and on development of hardware and hardware and software to process and analyse data basically from single and split-beam transducers. Experiments on ice, field-works in rivers and modelling are important parts of our work. We measure the direct and reflected sound with hydrophones and echo sounders. Finite element method and ray tracing are applied in the modelling.
Fish echoes in shallow water frequently take on multiple echo characteristics while fluctuations in the background takes on single fish characteristics. Hence, single echo detectors based on single fish echo criteria such as echo-intensity, length, shape and phase stability does not work well. To solve this we have developed an alternative single target detector working with the frequency spectra of the echo data. In addition to the single target detector, tracking and classification is important part of our fish counting model.
The sonar teem at the department of physics consist of Torfinn Lindem, my self and at the moment four Ms.Sci. students.
(This paragraph
was last updated 27.05.2002)
Development
of hydroacoustic methods for fish detection in shallow waters
Ref: Balk, H., 2001. Development of hydroacoustic methods for fish detection in shallow water, Faculty of Mathematics and Natural Science, University of Oslo 309 p. ISSN 1501-7710
Management of salmon stocks from various regions is of great importance. Optimal management can only be achieved with knowledge of the size and the changes in the stocks. Hence, monitoring methods are important. In marine fisheries, split-beam echo sounders are frequently applied to monitor fish. In recent years this hydroacoustic fish detection method has been applied in many rivers. Aligning one or a few transducers horizontally provides a simple way to monitor major parts of a river's cross-section.
However, the horizontal shallow water application introduces new problems related to the acquisition, analysis, and interpretation of the sonar data. Fieldwork has been carried out in lakes and rivers, and a systematic analysis of these problems has been made. From the experience and the studies of the recorded material, new methods have been developed. Signal processing based on image analysis and classification theory is introduced, and promising results have been achieved.
Read the thesis. (html)
(Last updated 23.05.2002)
Digitalisation
of sonar (master thesis)
During the years 1994..1996 I wrote my master thesis "Digitalisation of sonar". It
describes the development of a hardware-software sonar system based on one to
four transmitters / receivers connected in a chain and controlled by a laptop.
High dynamic was gained by applying tuned passive circuits in the front end,
and splitting the signal into three separate channels with different gain. A
gain detector switched between the channels before sampling. To gain sufficient
speed for real-time processing in an ordinary laptop running Win3.1 through the
parallel port, a virtual device driver was written in assembly to replace the
standard parallel port. Presenting echograms in real-time was also challenging
and parts of the thesis was assigned to studies of data transport and screen
updating in windows. The thesis consists of a total of 456 pages describing the
hardware and software development and testing.
The thesis is available at the University library (Bibsys)
(Last updated 22.01.2002)
Publications, proceedings and reports
Publications and presentations
2009 Balk, Helge; Lindem, Torfinn. Target
detection in data from splitbeam echosounders and multi beam sonar systems.
Invited talk Evening seminar at the
Norvegian society for image analysis and pattern recognition
2008 Tuser, Michael; Balk, Helge; Froutsova,
Jaroslava; Kubecka, Jan; Muska, Milan. Suitability of DIDSON acoustic camera for
quantitative fish stock assessment by mobile surveys. Symposium on the
Echosystem Approach with Fisheries Acoustics and Complementary Technologies
(SEAFACTS); 2008-06-15
2008 Rudstam, Lars G.; Knudsen, Frank R.; Balk,
Helge; Gal, Gideon; Boscarino, Brent T.; Axenrot, Thomas. Acoustic
characterization of Mysis relicta at multiple frequencies. Canadian Journal of
Fisheries and Aquatic Sciences 2008 ;Volum 65.(12) s. 2769-2779
2008 Rakowitz, G; Herold, W; Fesl, C; Keckeis, H;
Kubecka, J; Balk, Helge. Two methods to improve the accuracy of target-strength
estimates for horizontal beaming. Fisheries Research 2008 ;Volum 93.(3) s.
324-331
2008 Rakowitz, G; Herold, W; Fesl, C; Keckeis, H;
Kubecka, J; Balk, Helge. Two methods to improve the accuracy of target-strength
estimates for horizontal beaming. Fisheries Research 2008 ;Volum 93.(3) s.
324-331
2008 Kubecka, Jan; Balk, Helge; Drastic,
Vladislav; Frouzova, Jaroslava; Gassner, Hubert; Herzig, Alois; Jarolim,
Oldoich; Juza, Tomas; Kratochvil, Michael; Vasek, Mojmir. Large-scale acoustic surveys of an extremely
shallow lake: Neusiedler See, Austria. Symposium on the Echosystem Approach
with Fisheries Acoustics and Complementary Technologies (SEAFACTS); 2008-06-15
- 2008-06-21
2008 Jurvelius, Juha; Knudsen, Frank R.; Balk,
Helge; Marjomäki, Timo J.; Peltonen, Heikki; Taskinen, Jouni; Tuomaala, Antti;
Viljanen, Markku. Echo-sounding
can discriminate between fish and macroinvertebrates in fresh water. Freshwater Biology 2008 ;Volum 53.
2008 Gjelland, Karl Øystein; Knudsen, Frank;
Balk, Helge. Bias in
swimming speed estimates from splitbeam acoustics should be corrected for with
smoothing. Symposium on the Echosystem Approach with Fisheries Acoustics and Complementary
Technologies (SEAFACTS); 2008-06-15
2008 Froutzova, Jaroslava; Kubecka, Jan; Balk,
Helge. Fat echoes of oblique aspects : consequences for fish single echo
detection. Symposium on the Echosystem Approach with Fisheries Acoustics and Complementary
Technologies (SEAFACTS); 2008-06-15
2008 Drastik, Vladislav; Hohausova, Eva; Kubecka,
Jan; Balk, Helge; Froutsova, Jaroslava. Classification of fish and plant echoes
in acoustic surveys. Symposium on the Echosystem Approach with Fisheries Acoustics
and Complementary Technologies (SEAFACTS); 2009-06-15
2008 Balk, Helge; Lindem, Torfinn; Kubecka, Jan. Split beam versus multi beam for
monitoring migrating fish in rivers and shallow lakes. ICES Symposium on the
Ecosystem Approach with Fisheries Acoustics and Complementary Technologies;
2008-06-15 - 2008-06-20
2008 Balk, Helge; Lindem, Torfinn. Analysis and
visualization of data from DIDSON Acoustic camera. 31-th Scandinavian symposium
on Physical Acoustics; 2008-01-27
2008
Hohausova, E; Kubecka, J; Frouzova, J; Husak, S; Balk, Helge.
Experimental biomass assessment of three species of freshwater aquatic plants
by horizontal acoustics. Journal of aquatic plant management 2008 ;Volum 46.
2007 Rudstam, Lars G.; Gal, Gideon; Balk, Helge;
Knudsen, Frank R.; Axenrot, Thomas; Boscarino, Brent. Multiple acoustic
frequencies increase our ability to discriminate between fish, mysids and
zooplankton. IAGLR 2007; 2007-05-28 - 2007-06-01
2007 J.
Jurvelius, F.R. Knudsen, H. Balk, T.Mariomäki, H. Peltonen, J. Taskinen,
A.Tuomaala, M.Viljanen. Echo-sounding
can discriminate between fish and macroinvertebrates in fresh water Freshwater
Biology (2007) doi:10.1111/j.1365-2427.2007.01944.x
2007 Balk, Helge; Lindem, Torfinn; Kubecka, Jan; Frank, Knudsen. Recent advances in solving signal-to-noise problems in fisheries acoustics
Keynote
talk at the FSAMPL07 conference, Ceske Budejovice, Czech Republic, September.
11-15, 2007.
2007 Balk
Helge. Analysis of data from high frequency multi beam sonars. Scientific talk
at the DIDSON workshop arranged by the
2006 Balk, Helge,
Introduction, presentation and theory for multi-frequency
hydroacoustics. Invited to teach and partly lead the Multi frequency workshop
at Cornell University; 26.08.2006 - 03.09.2006
2006 Balk,
Helge. Sound waves and fish abundance. Talk at the University of Mildura (Au)
Invited by CSIRO to assist establishing hydro-acoustic 29.05.2006 - 29.05.2006
2006 Balk, Helge;
Lindem, Torfinn; Kubecka, Jan. Enhenced Crossfilter detector for target detection in data from
echosounders. 29th SCANDINAVIAN
SYMPOSIUM ON PHYSICAL ACOUSTICS; 29.01.2006 - 01.02.2006
2005
Balk,.H. 2005. Linear kretselekronikk. Unipub. 293p. Tutorial book in linear
circuit analysis with focus on Fourier and Laplace transformations for the UiO
course FYS3220.
2005
Peltonen, H; Balk, Helge. The acoustic target strength of herring (Clupea
harengus L.) in the northern
2005 Frouzova,
J; Kubecka, J; Balk, Helge; Frouz, J. Target strength of some European fish
species and its dependence on fish body parameters. Fisheries Research
2005;75:86-96
2005 Balk,
Helge. New methods for fish and bottom detection in data from split beam echosounders.
Invited to talk and partly lead a seminar arrange by Ifremer, IRD and INRA ;
27.07.2005 - 29.07.2005
2005 Balk,
Helge. A Ph. D. Class on Marine Bioacoustics. 29.05.2005 - 08.06.2005 Tjarnø
(Se). Invited teacher for the
echo-sounder part of the class. Plenum lecturer, field work and laboratory
classes.
2005 Balk,
Helge; Lindem, Torfinn; Kubecka, Jan. New single echo detection methods for
shallow water fisheries acoustics. [Scientific talk]. 135th Annual Meeting of
American Society of Fisheries in Anchorage; 11.09.2005 - 15.09.2005
2005 Balk,
Helge. New methods for fish and bottom detection in data from split beam
echo-sounders. Seminar arrange by Ifremer, IRD and INRA at Ifremer in Brest;
27.07.2005 - 29.07.2005
2005 Balk, Helge; Lindem, Torfinn; Kubecka, Jan.
New single echo detection methods for shallow water fishery acoustics
[Vitenskapelig foredrag]. 149'th Meeting of the Acoustical Society of
2004 Balk,
H. and T. Lindem, 2004. Sonar4 and Sonar5-Pro. Post processing system. Operator
manual v5.9.4. Lindem Data Acquisition. 405 p.
2004 Balk,
Helge. Reflection and diffraction of sound waves in shallow water and how this
influences the sonar equations [Scientific talk]. Swedish acoustic meeting;
25.10.2004 - 26.10.2004
2004 Balk,
Helge. Presentation of research results. Advanced analysis methods for
fisheries acoustics. Detection methods for data characterized with low signal
to noise ration [Scientific talk]. Workshop on hydro-acoustic methods; 31.03.2004
- 04.04.2004
2003 Balk,
Helge; Lindem, Torfinn. Fish detection based on spectral differences in the
echogram's range and temporal domain [Scientific talk]. ICES Fast meeting in
Bergen; 18.07.2003 - 21.07.2003
2003 Balk,
Helge; Lindem, Torfinn. Fish detection based on spectral differences in the
echogram's range and temporal domain [Scientific talk]. ICES Fast meeting in
Bergen; 18.07.2003 - 21.07.2003
2003 Balk, Helge; Lindem, Torfinn. A new method
for single target detection [Poster]. 6th ICES Symposiom "Acoustics in
fisheries and aquatic ecology" 2003. Published in: Book of Abstracts
2002
Lindem, T. and Balk, H. 2002. Measurements of acoustic sound fields in a
shallow river. Poster
at ICES meeting in
2002 Balk, H. and Lindem, T. 2002. Fish detection in rivers with split-beam sonars
Proc.
25’th Scandinavian Symp. Phys Acoust., Vol. No. 2002-04.
2002 Balk, H. and
Lindem, T. 2002. A new method for single target detection in shallow water. Poster at ICES meeting in Montpelier Fr.
2002 Lindem, Torfinn;
Balk, Helge; Vibeke, J.; Kjølerbakken, K. M.. Measurements of acoustic sound fields in a
shallow river [Poster]. ICES Symposium on acoustics fisheries and aquatic
echology 2002. Published in: Book of abstracts
2001 Balk,
H., 2001. Development of hydro-acoustic methods for fish detection in shallow
water. Oslo Dissertation for the degree of the Dr.Sci. 2001. Factulty of
mathematics and natural sciences. University
of Oslo ISSN 1501-7710 Nr. 137. 309 p.
2001 Gjelland, Karl
Øystein; Balk, Helge; Bøhn, Thomas. Laksetelling i Reisa med ekkolodd sommeren
2001 �
et prøveprosjekt. Tromsø: Norges Fiskerihøgskole, Universitetet i Tromsø 2002.
32 s.
2000 Balk, H. and Lindem, T. 2000. A method for separating fish from noise
in Sonar data characterized by low signal to noise ratio. Patent PCT/No00/00288
2000 Balk, H. and Lindem, T. 2000. Improved fish detection in data from
split beam transducers. Aquat. Living Resour. 13 (5), 2000, 297-303.
2000 Balk,
Helge; Lindem, Torfinn. Improved fish detection in data from split-beam sonar.
Aquatic Living Resources 2000;13:297-303
1999
Lindem, Torfinn; Balk, Helge; Knudsen, Frank R.. Sound propagation through
shallow water can make unexpected modification to fish echoes recorded with a
horizontally looking split beam system [Vitenskapelig foredrag]. 2nd
International Shallow Water Fisheries Sonar Conference 1999
1999 Balk, H. and Lindem, T. 1999. Fish tracking in shallow water by
applying image processing. Proc. 22’th Scandinavian Symp. Phys Acoust., 1999. Vol. No.
429904. pp 1-2.
1999
Lindem, Torfinn; Balk, Helge. Problems related to Time Varied Gain (TVG) and
phase measurements with elliptic split beam transducers in shallow water, -
some observations [Poster]. 22nd Scandinavian Symposium on Physical Acoustics
1999. Publisert i: NTNU Scientific/Technical Report No.429904
1998 Balk, H.
and Lindem, T. 1998.
Hydroacoustic fish counting in rivers and shallow waters, with focus on
problems related to tracking in horizontal scanning sonar’s. Proc. 21’th Scandinavian Symp. Phys Acoust., Vol. No. 1998-04 pp. 21-22.
1996
Balk, H. 1996. Digitalisation of Sonar, Department of Physics,
.
(This paragraph was last updated 01.06.2009)
Links currently not available……………………………..
Additional
background articles (10Mb) Place
these files in a subfolder named
/help_Articles/Balk_Lindem_2001 (Last updated 18.12.2002).
Download additional tool programs. (1.2Mb). The
files must be located in the same folder as the program. (Last updated
18.12.2002).
The following links
are currently not working 01.08.2003
·
Fish
tracking in shallow water by applying image processing. 22'th Scandinavian
Symposium on Physical Acoustics Ustaoset, February 1999. Proceeding (pdf)
·
Transferring
a well known vertical counting-method to horizontal use in river
systems. 21'th Scandinavian Symposium on Physical Acoustics Ustaoset
Høyfjellshotell, 31 January -
·
Digitalisation
of sonar (Balk. H., 1996) Thesis for the degree of the Ms. Sci.
·
Aqua-culture
in
·
Aqua-culture
in
·
Pictures and echograms
from the field work in Tana 1999 . (html)
·
Report
from fieldwork in the river Tana summer 1998 Photos (jpg) , About Tana ( pdf Norwegian)
PhD
Download
thesis: Pdf
(2.3Mb), Interactive
word version (14Mb)
Download summary
(72kB) presented at the 25nd Scandinavian Symposium on Physics
Acoustics Ustaoset 27-30 January 2002
Download first
lecture for the degree of the doctor scientiarum. Classification.
(Norwegian, Power Point presentation)
Download second
lecture for the degree of the doctor scientiarum. Biomass
estimation (English, Power Point
presentation )
MsC
Download Pdf version (Digitalisering
av sonar, Balk, H., 1996)". (Norwegian only)