Wednesday, February 13, 2013

Legacy applications of commercial sonar

At Contour Innovations we stand on the shoulders of giants who proved commercial depthfinders are precise scientific instruments for the measurement of aquatic plant abundance and distribution in lakes.   As early as 1980, researchers saw the potential for fathometers/chart recorders/depth finders/sonar/echosounders - whatever you want to call them - to substantially reduce time, effort, and cost in assessing aquatic plant communities in lakes (Maceina and Shireman 1980).

The commercial sounders of the 1980's had only a fraction of the power and resolution of what Lowrance manufactures today (not to mention integration with GPS) and investigators still boasted of the quality and cost-effectiveness of the data acquired.  Here are some excerpts:

Maceina and Shireman (1980): "The principle advantage of utilizing a recording fathometer for vegetation surveys is that savings in time and manpower can be accomplished.  In Lake Baldwin, 14 transects covering a total distance of 11.3 km were completed in three hours." p 38.

Duarte (1987): "Direct harvesting is an expensive and time-consuming procedure (see Downing and Anderson 1985).  Two SCUBA divers require 20 min on average to harvest the biomass of six replicate quadrats at a single depth.  In contrast, six replicate echosounder transects require only 8-35 min to obtain biomass estimates for all depths, with the actual time required dependent on the littoral slope and the depth to which the plants grow.  Additional advantages of the echosounder method are (1) a continuous record of the vegetation, rather than at discrete depths only, with the latter resulting in inaccuracies when the mean biomass values are estimated, (2) nondestructive sampling, which allows monitoring of the growth of stands over time and (3) simultaneous recording of other variables such as percent cover (Stant and Hanley 1985), volume occupied by the submerged vegetation, and littoral slope (Duarte and Kalff 1986), which influences macrophyte biomass." p. 734

In fact, Duarte (1987) publishes biomass prediction equation from acoustic estimates of plant height (a ciBioBase output) for 22 aquatic plant species.

Thomas et al. (1990): "Fortunately, shallow range (0-7 m) chart recorders are standard on many low cost (less than $400) commercial echosounders, so the data acquisition equipment costs are relatively low with respect to fisheries acoustic assessments, which makes this procedure relatively nontechnical and very cost effective" p. 810

The concept of using commercial acoustics for mapping lake bottoms is established and proven.  Contour Innovations has refined, streamlined, and automated the methodology with ciBioBase and delivers an intuitive visualization of the complex underwater world we call littoral zones.
A Raytheon DE-719 "fathometer" relic when plant biovolume was measured on paper charts with the use of planimeters.  Photo from www.euronet.nl.


Paper chart from a Raytheon DE-719 displaying dense hydrilla canopies and bottom in a central Florida lake.  Reproduced from Maceina and Shireman 1980; J. Aquat. Plant Manage.

Classic Literature
Duarte, C.M. 1987. Use of echosounder tracings to estimate the aboveground biomass of submerged plants in lakes. Canadian Journal of Fisheries and Aquatic Sciences 44: 732-735

Maceina, M and Shireman, J. 1980. The use of a recording fathometer for determination of distribution and biomass of Hydrilla. Journal of Aquatic Plant Management 18:34-39.

Maceina, M.J., Shireman, J.V., K.A. Langland, and D.E. Canfield Jr. 1984. Prediction of submerged plant biomass by use of a recording fathometer.  Journal of Aquatic PlantManagement 22: 35-38.

Stent, C.J. and Hanley, S. 1985. A recording echosounder for assessing submerged aquatic plant populations in shallow lakes. Aquatic Botany 21: 377-394


Thomas, G.L., Thiesfeld, S.L., Bonar, S.A., Crittenden, R.N., and Pauley, G.B. 1990. Estimation of submergent plant bed biovolume using acoustic range information. Canadian Journal of Fisheries and Aquatic Sciences 47: 805-812.




1 comment:

  1. Interesting update on 21st century applications of Sonar for mapping bottom environments.

    http://www.sciencedirect.com/science/article/pii/S0380133013000300


    Abstract
    Highlights
    Keywords
    Introduction
    Table 1
    Underwater acoustic remote sensing and theory of operation
    Single-beam echo-sounders


    Dual-beam and side scan sonar systems


    Multi-beam sonar
    Imaging sonar systems

    Doppler sensing
    Point measurement systems
    Profiling measurement systems


    Next steps in advanced acoustic sensors



    Acknowledgments
    References


    Journal of Great Lakes Research
    Available online 2 April 2013

    In Press, Corrected Proof — Note to users


    A review of low cost underwater acoustic remote sensing for large freshwater systems

    Guy A Meadows (Michigan Technological University)

    Abstract:
    In recent years, low cost and highly accurate underwater remote sensing instruments and technologies have advanced at an astonishing rate. Intense competition among manufacturers, coupled with advances in digital signal processing has brought about these breakthroughs, all to the benefit of the scientific community. Commercial Off the Shelf Technology (COST) is now available and incorporated into current acoustic sensors, with quality and resolution that was previously reserved for only large-scale ocean exploration. The corollary to this observation is that the entire field of acoustic remote sensing of the aquatic environment is rapidly evolving and is likely to continue to do so over the next decade. Acoustic bottom mapping, Doppler sensing and remote and autonomous vehicle imaging systems are now becoming commonplace for large lake science and are approaching maturity. Given this evolution, this summary reviews two major categories of underwater, acoustic remote sensing technologies; bottom mapping systems and Doppler sensing systems. Bottom mapping systems are primarily used to determine the presence of the bottom, map its features and classify its composition. Doppler systems make use of target motion to deduce the velocity of the target, in up to three spatial dimensions. For each category of acoustic remote sensing a brief description of the theory of operation is provided, followed by examples of the types of data produced by the technology. When possible, estimates of range and accuracy of typical units in each class is provided. Finally, examples of new utilizations of combined remote sensing technologies are discussed.

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