In the 8+ years BioBase has been in service, we’ve seen our share of sonar logs and maps (both good and bad). We’ve learned some things and improved back-end processes that have resulted in you getting better maps processed faster. But we’ve also learned from you, our users, about strategies and techniques that result in better outcomes, and what to avoid. Here are eight of those lessons learned:
1. Good transducer installation is critical
You could be the most experienced hydrographer in the world and execute the perfect survey design, but your map will be mostly worthless if your transducer is not securely attached to your boat or is slanted at an angle. We’ve devoted a fair amount to this topic in previous blogs, so we won’t dwell on it here. The two key take aways are: 1) ensure the transducer is installed straight in all directions keeping in mind the slant of the hull in the water fully loaded. Replicate that tilt with your tongue jack when installing your transducer. 2) Install the transducer where the flow of water is smooth and laminar over the transducer face at all speeds. If you lose your transducer signal as the boat speeds up, you probably have an issue with cavitation (water turbulence) around the transducer face. Adjust the transducer height (sometimes only a very small amount) or move it away from rivets or anything else near the hull that could cause cavitation. One of the benefits of working with consumer devices like Lowrance and Simrad is that there is a wealth of online self-help resources and service centers that can help you install your transducer correctly. A simple Google Search “Lowrance Transducer Installation” will turn up all the resources you need. This one from Lowrance is one of our favorites. If you have multiple survey boats and want to make your unit portable, I strongly recommend purchasing and installing multiple transducers on all of your boats rather than a portable transducer bracket. In the grand scheme of things, consumer-sonar transducers are cheap and the consistent results you will get from a firmly mounted transducer is worth it!
EcoSat is a first of its kind semi-automated satellite imagery processing tool that’s part of the BioBase cloud mapping platform (Figures 1 and 2). EcoSat is helping several US states and countries map and monitor the status of shallow growing aquatic vegetation and benthic habitats. In this blog, we discuss several tips and tricks about how practitioners can maximize the accuracy and precision of their EcoSat vegetation maps.
We are grateful to the aquatic research community who continue to verify and validate Consumer Sonar Technologies (Lowrance) and BioBase automated mapping platform to produce scientifically valid outputs that benefit aquatic conservation. We are excited to see the recent publication of research out of the University of New Brunswick that evaluated the accuracy and precision of Lowrance and BioBase’s EcoSound depth and vegetation outputs. The research is published in the open access journal Diversity and can be downloaded here. Below is the abstract
The development of consumer hydroacoustic systems continues to advance, enabling the use of low-cost methods for professional mapping purposes. Information describing habitat characteristics produced with a combination of low-cost commercial echosounder (Lowrance HDS) and a cloud-based automated data processing tool (BioBase EcoSound) was tested. The combination frequently underestimated water depth, with a mean absolute error of 0.17 ± 0.13 m (avg ± 1SD). The average EcoSound bottom hardness value was high (0.37–0.5) for all the substrate types found in the study area and could not be used to differentiate between the substrate size classes that varied from silt to bedrock. Overall, the bottom hardness value is not informative in an alluvial river bed setting where the majority of the substrate is composed of hard sands, gravels, and stones. EcoSound separated vegetation presence/absence with 85–100% accuracy and assigned vegetation height (EcoSound biovolume) correctly in 55% of instances but often overestimated it in other instances. It was most accurate when the vegetation canopy was ≤25% or >75% of the water column. Overall, as a low-cost, easy-to-use application EcoSound offers rapid data collection and allows users with no specialized skill requirements to make more detailed bathymetry and vegetation maps than those typically available for many rivers, lakes, and estuaries.
One of BioBase’s strengths is its simplicity. You don’t need an advanced engineering degree in hydrography to make a high quality bathymetric map with an off-the-shelf sonar device. If you have your transducer installed correctly, settings correct on your Lowrance, and achieve good coverage on your waterbody of interest, then BioBase’s EcoSound algorithm will produce a very precise, high quality bathymetric map output within minutes of upload to biobasemaps.com. The speed and ease of bathymetric mapping wins the day for many of our users, but perhaps even more valuable, is the benchmark you are setting for an unknown day in the future when something has changed on the lake and you need to have some “historical” information to understand how much change has taken place
Use Case: Monitoring Sedimentation
One of our most frequently asked questions by new users is “will BioBase measure sediment thickness or the depth of the sludge?” This was a source of a recent blog. Interestingly, the answer is different depending on how long our customers have been using BioBase. For the user who has no prior information about how deep the lake or pond is supposed to be, BioBase may not provide detailed enough information about the actual thickness of the sediment (sediment depth is correlated with EcoSound hardness but it is highly variable; see this blog for further details). However, for the pond management consultant who happened to “BioBase” a client’s pond in 2013 while she happened to be on site for another matter and is now hearing from the client in 2019 that his pond is “filling in,” the answer about whether BioBase can tell him how much sediment has filled in is a most definite yes! For this pond consultant, it was a most fortuitous (or perhaps prudent?) thing that she decided to voluntarily map her clients pond in 2013. Now with a 2019 survey, she can precisely quantify exactly how much sediment has accumulated and where over the 7 years by doing a simple subtraction of the depth and water volume between surveys and comparing maps. The comparison of maps can be done a fancy GIS way like described in this blog. Or a quick and easy way through BioBase (see examples below).
We’re excited to announce the launch of the new biobasemaps.com website! You’ll find an image-rich professional look and feel as well as information segmentation into solutions and features that speak directly to the markets we serve (Aquatic Plants, Fisheries, Water Resources, Private Ponds, Coastal).
New visitors to biobasemaps.com will also see more information about our optional GIS Services that can take your BioBase maps and tailor them to your precise needs regarding image size, contour interval, custom legend, logos, etc.
Dabbling in GIS? We can help you get started in QGIS
Many of you also come to us with questions about how to do more with your BioBase outputs (e.g., custom contouring, water volume calculations, spatial data analyses). To empower you to fully leverage the potential of BioBase outputs we have prepared several step-by-step QGIS tutorials to get you the outputs you require for your work. See our Support Resources page for these tutorials along with other useful self help resources
I frequently get inquiries from current and prospective BioBase users about the accuracy of consumer-grade Lowrance GPS and whether survey-grade 3rd party receivers capable of differential correction (DGPS) or receiving positions from multiple satellite constellations (Global Navigation Satellite System – GNSS) could be used with Lowrance and processed with BioBase.
The first question about accuracy prompted a test in March of 2013 with a Lowrance HDS tested side-by-side with a Trimble GeoXH. I was pleased to find less than 1m deviation on average from post-processed Trimble DGPS positions. One meter accuracy and precision is typically sufficient for most boat-based mapping applications. Still, prerequisites for some projects require DGPS, and there are a number of BioBase users who have and still would prefer to have DGPS generated positions to use when logging trips. Thus, I was interested in exploring the capabilities of networking positions from a third-party receiver into a Lowrance HDS.
River channel thalwegs (the line of lowest elevation within a valley or watercourse) are often dynamic, and sometimes hidden features of large river systems. Especially low slope or impounded systems. The thalweg is a critical geomorphological feature of river and reservoir systems and affects everything from sediment transport, to fisheries habitat, to algae or invasive plant control.
Thus a good bathymetric contour map is a necessary pre-requisite for effective river and reservoir management. Here, we walk you through how to use new real time technologies (C-MAP’s Genesis Live) to produce smooth, precise, and accurate maps of hidden river thalwegs all within one trip to the site and with automated post-processing with BioBase’s EcoSound. We’ll use an annotated image gallery to take you through this process.
What is EcoSat?
EcoSat delivers a one-of-it’s-kind semi-automated cloud processing of very high resolution satellite imagery to map nearshore vegetation and coastal benthic habitats. EcoSat uses the latest multi-spectral imagery from reputable providers such as Digital Globe (World View 2,3 and 4), Airbus Defence and Space (Pleiades), and ESA’s Sentinel program and industry standard image processing techniques. Sophisticated Amazon Web Service cloud infrastructure rapidly processes imagery, creates reports and imagery tiles, and delivers detailed habitat maps to user’s BioBase dashboard where it can be analyzed and shared. Average turnaround time from imagery tasking order to delivery of results is 60 days. The rapid and standard processing methods are allowing entities like the Florida Fish and Wildlife Conservation Commission to establish regular monitoring programs for emergent vegetation. The extremely long and expensive one-off nature of conventional remote sensing mapping projects using non-repeatable tailored techniques has prevented natural resource entities from assessing the degree that habitats are changing as a result of environmental stressors such as invasive species invasions and climate change.