Mapping Ponds with BioBase

As an addendum to our blog series on rapid, portable applications we wanted to experiment with a "thru-hull" mount of the 83/200 khz Lowrance HDS transducer on a kayak for mapping storm water retention ponds in an urban area of Minnesota (City of Maple Grove).  Electrician putty (sold as "Duct Seal") available for a few dollars at the neighborhood hardware store worked as a perfect medium for this application.  Follow the series of pictures and captions to see how this worked!

Electrician putty or "Duct Seal" available at most hardware stores can be used for shoot "thru-hull' applications on kayaks or canoes

Figure 2. A 83/200 Lowrance skimmer transducer secured to the hull of a polyethylene kayak by duct seal putty. Care should be taken to remove all air bubbles from the mold before pressing in the transducer

James Johnson from Freshwater Scientific Services LLC (www.fixmylake.com) gets his Lowrance HDS-5 all set to log data. 

Tracks showing a concentric circle approach toward mapping ponds smaller than 10 acres.  This one is 3 acres located in an urban area of Minnesota near Minneapolis (Maple Grove).  Data took 30-min to collect

Blue-scale bathymetric output created after 10-minutes of data processing time by Contour Innovations servers after upload.  Map was produced by 1,000 passively acquired GPS and bottom points.  All map outputs (e.g., water volume or hardness - next picture) can be analyzed in your private ciBioBase online account or exported to GIS for more sophisticated data analyses and layering

Bottom hardness automated output automatically created along with bathymetric and aquatic vegetation layers  in ciBioBase.  Areas that are maroon represent hard areas that remained from the original construction of the pond.  Soft areas are represented by the lighter brown colors and represent sand deltas from parking lot runoff.  Hardness and bathymetric outputs can be used to assess whether storm water retention ponds require maintenance and where specifically to focus efforts

New ciBioBase Website and Mapping Dashboard

At Contour Innovations, ease of use, organization, and user experience are top priorities.  We recognized that our old site wasn't the best it could be, so over the last few months the website and dashboard have been rebuilt from scratch.  We've listened to all the questions our customers had and attempted to incorporate all of these into the new dashboard.   The result is a sleek, user friendly dashboard with a great user experience.  It's fast and has the features to sort, organize, and use the important data you upload to your account for automated processing.  Now you can maximize your BioBase experience!

New features include:

• Tagging - You are now able to add descriptive tags to each of your trips for better sorting
• Improved Search Capabilities - search all categories generally by user last name, lakes, and even tags
• Collapsing Trip Organization by Lake - Trips are categorized by lake in the dashboard and only loaded when you want them
• Trip Track Quick View - Each trip in the dashboard provides a snapshot of where your track is on the water body for quickly identifying a survey area
• Sort by Date - Trips can be filtered by date range so you're only looking at the trips you want to see
• Advanced Searching - This feature will allow you to sort by a specific category like file name, tags or water bodies
• Support Tab - Many of the methods that we blog about are now available as PDFs and step-by-step Powerpoint documents in your account
• Trip Support Request - Quick boxes within each trip allow you to communicate your questions directly to QC experts for a specific file or merge
• Overall cleaner look for a better user experience!

This dashboard should be much easier to use and was designed so the things you are looking for are right where they should be.  We're always interested in hearing from you so please log into your account and check out!  Let us know what you think and if you have questions about any of the new, powerful features

Detect Change in Your Lake Before it's Too Late!

Citizens all over the globe love their lakes and go to great lengths and spend lots of money to protect and manage them.  In the US, the Environmental Protection Agency supports a multitude of State, Local, and citizen efforts to monitor water quality in lakes and has implemented a rigorous National Lakes Assessment.  Despite these efforts, lakes across the nation continue to be impacted from runoff pollution and invasive species proliferation under our noses. How does this happen?

Unfortunately, despite well-intentioned efforts to monitor various lake parameters, established monitoring methods such as water sampling from the middle of the lake or presence/absence surveys of aquatic plants often do not change significantly until there has been a fundamental shift in a lake’s ecology.  We blogged about this concept in more depth last year.

The risks of not monitoring sensitive indicators are high.  First, once a lake has “tipped” into a new regime, it’s difficult if not impossible to restore the lake to its original condition.  Second, a lot of money is on the table for either watershed protection/restoration or lake management (e.g., herbicide or other remediation costs).   This reality demands that citizens and lake managers monitor lake parameters that respond quickly to environmental change and lake management interventions such that environmental or economic costs are kept minimal.

Aquatic plant abundance in lakes is responsive to change, frequency of occurrence is not

We discussed an interesting case study near the end of our Point-Intercept on Steroids blog last October about a moderately nutrient-polluted lake in Minnesota infested with non-native Eurasian watermilfoil.  A whole-lake herbicide treatment was applied to target and kill the Eurasian watermilfoil.  Unfortunately, there was little else growing in the lake that was not vulnerable to the herbicide.  The herbicide wiped out almost all submersed vegetation.  This had negative effects on the water clarity and fish habitat in the lake.  In glacial lakes, aquatic plants are often critical components of healthy lakes.

The fact that the herbicide “wiped out almost all vegetation” would have been nothing more than the desperate cries of a Fisheries manager or a concerned citizen who saw it “with their own eyes” if it was not for a hydroacoustic assessment of plant abundance that occurred before and two years following the treatment (Valley et al. 2006; Figure 1).  Concurrently occurring rake surveys of frequency of occurrence, although important for determining what species were growing at the time, did not detect the almost complete loss of submersed vegetation in the lake (Figure 1).  Figure 2 demonstrates why rake frequency surveys are so insensitive to changes in abundance.  To put it concisely, rake surveys are not abundance surveys, they are species occurrence surveys.  Large changes to the lake must occur before change is reflected in species frequency data.

Figure 1.  Frequency of occurrence of all plants estimated using the point-intercept method (numbers above bars) in a eutrophic Minnesota lake (Schutz)  treated with a whole-lake herbicide in June 2002.  The bars represent the whole-lake biovolume of aquatic vegetation in Schutz and a nearby reference lake (Auburn).   Average biovolume declined from 35% in 2002 before the treatment to 1.5% the year following the treatment.  Biovolume was assessed over the entire waterbody and more closely reflects the true changes in abundance than percent frequency or any other adaptation that uses qualitative estimations of abundance (e.g., abundance on a scale of 0-3).  Figure adapted from Valley et al. 2006

Figure 2.  Two drastically different environments that get the same data value (present) if a rake picks up the sprig in panel B.  Weighting by a rank (e.g., A = "3" or Abundant and B = "1" or Sparse) is only moderately more informative about true abundance since no quantitative judgement can be made by the ranks

Passive logging of acoustics by citizens to rapidly detect change in lakes


Lowrance™ HDS log up to 20 data points (pings) per second.  A GPS report of your location is automatically logged approximately every second.  Spend a couple of hours driving back and forth on your lake (like you may already do normally) and now you have a full system map incorporating 144,000 data points on plant abundance on a lake all summarized nicely in a map and summarized statistical reports (Figure 3).  By repeating this process multiple times throughout the year with other lake citizens (see our wisdom of the crowd blog) over several years, you will measure the “heartbeat” of your lake and begin to notice when an irregular rhythm shows up and what might be causing it.

Figure 3.  Sample output of vegetation abundance (red = vegetation near the surface, green = vegetation near the bottom, blue = no vegetation) and GPS tracks in a 235 acre Minnesota Lake.  Bathymetry, vegetation, and bottom hardness maps were created by simply logging acoustic data from Lowrance™ HDS, driving back and forth for 3 hours, and then uploading the data to ciBioBase

Infrequent plant species rake surveys or water sample monitoring in the middle of the lake will not give you the heartbeat of the lake; only a snapshot of the current conditions and whether your “patient” is in critical condition.  ciBioBase is your tool for good preventative lake health care.

Literature Cited

Valley, R. D., W. Crowell, C. H. Welling, and N. Proulx. 2006. Effects of a low-dose fluridone treatment on submersed aquatic vegetation in a eutrophic Minnesota lake dominated by Eurasian watermilfoil and coontail. Journal of Aquatic Plant Management 44:19–25.

Guest Blog: ciBioBase and Arctic charr habitat in Windermere, U.K.

By Dr. Ian J. Winfield and Joey van Rijn

The Arctic charr (Salvelinus alpinus) is well appreciated as an important fisheries species in many northern areas of the world.  In addition, it is equally important to evolutionary biologists because of this species’ frequent development of ‘morphs’ or 'types' and their bearing on our understanding of mechanisms of speciation (Figure 1).  In the U.K., this fascinating fish is also recognised as having great nature conservation value.

Figure 1.  A female (top) and male (bottom) Arctic charr from Windermere, U.K.  Photo courtesy of the Center for Ecology and Hydrology)

Windermere is England’s largest lake and has been at the forefront of several areas of Arctic charr research for many decades, with the notable exception of studies of their spawning grounds (Figure 2).  Despite their long appreciated significance for the coexistence of autumn- and spring-spawning Arctic charr types, local spawning grounds have not been studied in any detail since their original brief description in the 1960s.  At that time, laborious and spatially-limited direct observations by divers showed that spawning requires the availability of gravel or other hard bottom habitat.  New information on these critical areas is needed by ecologists and evolutionary biologists and, more urgently, by fisheries and conservation organisations responsible for the management of Windermere.

Figure 2.  Breathtaking view of Windermere's north basin; home to several spawning populations of Arctic charr.  Photo courtesy of Dr. Ian Winfield.

We are currently using the newly developed bottom hardness capability of ciBioBase to survey and characterise the spawning grounds of Arctic charr in Windermere.  Limited underwater video is being used for ground-truthing, but the combination of a Lowrance™ HDS-5 sounder with ciBioBase is allowing us to investigate the known spawning grounds with unprecedented speed (Figure 3).  For the first time, we have been able to document in detail the bathymetry and bottom features of a long-monitored (for spawning fish) spawning ground just north of the island of North Thompson Holme in the lake’s north basin.  ciBioBase is also enabling us to examine other known spawning grounds in Windermere and to expand our coverage to other potential areas previously unstudied.

Figure 3. An example ciBioBase output of bottom composition on and around the Arctic charr spawning ground of North Thompson Holme in the north basin of Windermere

The rapidity of the field component of hydroacoustic surveys is well known.  ciBioBase now offers us a similarly fast method of hydroacoustic data analysis for key environmental characteristics in relation to the spawning of Arctic charr.  This new approach helps us to dramatically increase our return on investment and also allows us to review results within hours of coming off the water, leading in some cases to us adapting our field plans on the basis of initial results.

Dr. Ian J Winfield is a Freshwater Ecologist at the Centre for Ecology & Hydrology in Lancaster, U.K.  He has over 30 years of research experience in fish and fisheries ecology, hydroacoustics, and lake ecosystem assessment and management.  Dr. Winfield sits on several regional, national and international advisory boards and is the current President of the Fisheries Society of the British Isles (FSBI).

Joey van Rijn is an undergraduate student currently following a BSc. degree course in Applied Biology at the University of Applied sciences, HAS Den Bosch, in the Netherlands. He is experienced in ecological and particularly phenological research including work on temperature-induced differences between urban and rural areas in the timing of blossoming and leaf unfolding in shrubs.  He has also been involved with the development of fish ways for standing waters in the Netherlands. Joey is currently undertaking a research internship at the Centre for Ecology & Hydrology in Lancaster, U.K., where his research mainly focuses on using hydroacoustics to investigate Arctic charr spawning grounds in Windermere.

GPS Accuracy Test of Lowrance HDS

At Contour Innovations we put Lowrance HDS to the test for GPS precision and accuracy.  We know the importance of accurate maps but also recognize that “consumer-off-the-shelf” doesn’t mean it won’t provide the type of accuracy needed for accurate acoustic mapping.  The question lies more in how precisely accurate we can map aquatic environments with a “survey-grade” versus consumer GPS.  There are a lot of considerations when mapping from the surface of a water body.  Not only the accuracy of the GPS signal itself but the movement of a survey vessel on a liquid surface, wind, number of points surveyed, survey design, depth, acoustic cone degree, etc.  The list goes on because plants grow, you’re usually in a boat and water moves.  But, we can still investigate the precision of the WAAS corrected GPS from Lowrance HDS.  We were happy with our test results . . . but not surprised!

Units Tested:

• Trimble GeoXH 6000 Series (post processing DGPS correction to 12” accuracy and precision)
• Lowrance HDS-5 (WAAS-Correction Enabled)
• Lowrance HDS-7 Gen2Touch (WAAS-Correction Enabled)

Methods:

• Two individuals recording tracks while walking in same footprints, units held at chest level
• One individual recorded a track with the Trimble Unit while the other held the HDS
• Process repeated with the Trimble and HDS7 Touch
• Data collected in a 2-acre soccer field in Minneapolis surrounded by trees
• GPS Track lines from both units were uploaded to ArcGIS and converted to points
• Point layers from both units were spatially joined and distance from each HDS track point to the nearest Trimble GPS track point was calculated
• Conditions: Clear skies and HDOP (Horizontal Dilution of Precision) was less than 3
• Testing Completed March 14, 2013

One glaring item that can be pulled from the chart above is the accuracy of the Trimble unit before DGPS correction.  Published accuracy is much different than actual accuracy.  You can see from the numbers above that the DGPS correction didn’t adjust the Trimble track by much. When compared against the static HDS output, the comparison hardly changes (from an average difference of .71m between the HDS7 Touch and Trimble™ DGPS before correction to .69m after correction and .45m to .83 respectively for the HDS5).  Even after DGPS correction, both HDS units performed extremely well with significantly less than 1m average difference between tracks (.69m for HDS7 Touch and .83 for the HDS5).  

At Contour Innovations we’re focused on best and uniform geostatistical models, acoustic processing, number of data points, and other key standard operating/data collection procedures to create good maps.  The average difference shown in the chart above could even be significantly less than the size of your acoustic cone (depending on cone angle and depth).  Spacing of your sample points is also very important.  The Lowrance HDS system records up to 20 pings per second.  The precision and accuracy of a map created from such voluminous data sets is unmatched.  When analyzing this much data during your survey the geostatistical model and spatial references are substantially improved.

Geo-statistical algorithms:  No acoustic map is made up of a complete data set.  Data sampling points with less that 100% coverage still require a statistical model of extrapolation or interpolating of neighborhood points.  All aquatic maps are created with some level of geo-statistical model like kriging.  Ensuring accuracy of actual points will help decrease error coefficients of estimated data but more important is the type of geo-statistical model and spacing between data sampling sights.  There is a positive correlation of error coefficient and transect spacing.  We recommend transect spacing of less than 50m and even higher resolution and lower spacing depending on mapping objectives. 

Geostatistics is a branch of statistics focusing on spatial datasets originally developed to predict probability distributions.  A number of simpler interpolation methods/algorithms, such as inverse distance weighting, bilinear interpolation and nearest-neighbor interpolation, were already well known before geostatistics, but it goes beyond the interpolation problem.  Kriging, the model we use, is a group of geostatistical techniques used to interpolate the value at an unobserved location from observations of its value at nearby locations.  This means that as you collect data along a transect, those data can be used to predict unobserved data between points to a statistically significant probability.  A good geostatistical model and the number of sample point are key to a complete and accuracy map! 

A couple things to consider that could influence the accuracy and precision of your maps:

• Pitch, Roll and Yaw - Wave action or other movements of the boat as you take a physical samples
• Tree Cover - which isn’t as common when mapping open water like lakes
• Relation of GPS antennae to transducer - Even with 12 inch DGPS accuracy, if you’re standing 3 feet from your transducer your data points will be off.  If you take a core sample and enter the results into a GPS device, your boat could easily have drifted a lot more than your potential error.   With Lowrance HDS we provide an external antennae that can be mounted directly above your transducer so your data collection is happening at the point spot of your GPS signal.
• Overall Survey Design – The spacing of your transects is key as it relates to the ability to confidently make predictions in unsampled locations with your geo-statistical model. 
• Speed of Travel – When looking at a wide range of data collection techniques and methods, speed is always the biggest consideration for accuracy and coverage.

“Published Accuracy” is much different than actual accuracy.  A lot of this is a guarantee from the manufacturer to be less than a certain error threshold at least 60% of the time and is not a minimum.    

Because of this, there’s an opportunity to use scare tactics to discount the power of an off-the-shelf acoustic unit or GPS.  But, as we’ve described here, there’s a lot that goes into making a map!

We were very impressed with the performance of the WAAS corrected Lowrance™ HDS when compared against a system like the differentially corrected Trimble™ unit.  Though, we can’t say we’re surprised!

For more information on getting the best and most accuracy maps please contact one of our fisheries biologists and GIS experts.   

Lowrance™ and Trimble™ are registered trademarks of Navico, Inc. and Trimble Navigation Limited respectively.  Neither Company contributed, authorized, or requested this testing.       

ArcGIS Mapping Tutorials

ciBioBase is much more than a powerful data processing engine, it is also a complete data services package.  Contour Innovations' Biologists and GIS Specialists on staff can help you get the data products you need to efficiently assess waterbodies and make sense of your output.

With your subscription to ciBioBase, you get access to basic GIS and survey tutorials and technical support for everything from suggested transect spacing to ways of analyzing ciBioBase outputs.

Access to ArcGIS Tutorials are available to all subscribers

Tutorial 1 covers converting ciBioBase grid point feature outputs into raster datasets (requires Spatial Analyst extension for ArcGIS).  Although many types of analyses can be done on the grid point data, converting to raster allows users to run a wider range of analyses, custom contouring and imagery, compare maps over time, and to create unique maps (e.g., plant canopy height grid).

Tutorial 2 covers a step-by-step process of creating transect lines in ArcGIS, converting the shapefile to a .gpx file, and then uploading as tracks/trails to your Lowrance HDS.

Transect lines can be created using an ArcGIS utility and converting the shapefile to a .gpx file for importing into your Lowrance HDS as a Trail.

Pre-planning transect coverage and following the lines on your HDS Chart ensures complete coverage of the area you intend to map.

ciBioBase provides all the tools and features necessary to users with no GIS experience to automatically create maps and data reports to carry out effective lake monitoring and management.  Nevertheless, CI supports a range of custom GIS and data analysis needs through these tutorials and help from technical support staff.  CI also has a range of contract offerings for bigger GIS or data analysis training needs or special jobs.  ciBioBase is more than an algorithm, it is a service that helps lake managers and researchers more efficiently and precisely measure the aquatic systems they are charged with understanding and managing.

Contour Innovations Becomes ESRI Partner!

Contour Innovations is excited to announce a new partnership with ESRI (Environmental Science Research Institute), the company that has set the global standard for GIS (Geographic Information Systems).  This direction and partnership allows us to continue to grow and provide the type of tools our customers need to get the most out of their time on the water.  Our partnership with ESRI also supports our ability to expand our offerings to better support the GIS needs of our clients through GIS training webinars or custom GIS analyses and layouts using ciBioBase datasets. 

Contour Innovations has automated the basic GIS mapping and analysis tools (e.g., exported imagery, polygon tool and automated reports) with ciBioBase to produce a fully functional geospatial data analysis and warehousing platform for users who need "turn-key" solutions for water resource assessments.

However, the true power of ciBioBase lies in its ability to rapidly produce high resolution spatial datasets that can be exported out of ciBioBase and brought into to third party software platforms such as ArcGIS.  Multiple layers such as hyperspectral imagery of floating-leaf or riparian vegetation, upland terrain, plant species survey points, land use, or other in-lake features can all be overlain onto one image (Figure 1).

Figure 1. Example layout of aquatic plant biovolume (% of water occupied by vegetation) collected with Lowrance HDS depthfinders, processed by ciBioBase and brought into ArcGIS.  Species sampling points, aerial photos, or other spatial data layers can be overlain and displayed together.

Or, one could explore a range of powerful spatial and image analysis tools and extensions such as Spatial Analyst, 3D Analyst, Geostatistical Analyst or ArcGIS for Maritime: Bathymetry.  For example, the raster calculator feature of Spatial Analyst is an amazingly simple and powerful tool for spatially comparing and visualizing differences between map outputs and the creation of unique maps.  For instance, by simply multiplying a ciBioBase bathymetry raster grid by the vegetation raster grid, you can create a plant height grid (Figure 2).

Figure 2. Plant canopy height grid created by multiplying the ciBioBase depth grid by the biovolume grid using the raster calculator in ArcGIS Spatial Analyst.  Plant canopy height ranged from 0 (blue) to 10 ft tall (red)

The sky is the limit with regard to what you can do with ciBioBase datasets to help managers and researchers better understand and manage water, aquatic plant and fisheries resources.  Contact rayv@contourinnovations if you are interested in learning more about how CI can help maximize the value of your ciBioBase outputs.

Portable Lowrance HDS Units and ciBioBase

We recently sent out a mailer to our subscribers letting them know about the portability solutions that we have come up with.  Within minutes we received photos and details from many of our customers about how some they have used a little ingenuity to mount their Lowrance HDS units on unique water craft.  A couple examples include an inflatable for seagrass mapping on the west coast and an airboat for Florida lake mapping.

Coastal SeaGrass  Mapping

Rick Ware, Senior Marine Biologist with Coastal Resources Management, Inc. sent us these images of his set up for portability on their Achilles inflatable.  He commented that the same system can be used on his single and double kayaks as well.

Creative Kayak Set-up

 

When the water body you plan to map calls for a small craft . . .

Florida Air Boat

Dean Jones, with the University of Florida Extension sent us these images of his portable set up on the back of an air boat.  Since the early goings of vegetation mapping with ciBioBase we've worked hard to find and test a good mount for an airboat.  Dean has found a great solution that works every time!  He's getting great maps

Although the Lowrance units are always easy to install sometimes our users need a little creativity to meet their unique requirements.  Necessity is the mother of invention . . .

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.

Is StructureScan worth it? You be the judge

Debating whether it's worth the upgrade to the new HDS7 Gen2 Touch StructureScan bundle?  Outside of the bigger screen and more intuitive touch technology than its older generation HDS5 sibling, the imagery produced by StructureScan should be reason enough!

Below are the same areas of a lake in Minnesota using the traditional 200 khz signal (top) and the 455 khz DownScan add-on (bottom).  A school of fish hovering over Eurasian watermilfoil plants is clearly resolved in the bottom image.  The wider cone angle of the traditional signal cannot adequately resolve these minute features.  BioBase leverages both signals to produce accurate map data sets and reproduce spatially explicit imagery for plant cover typing.  Contact us if you would like to know more about HDS features or are interested in purchasing a unit