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!
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).
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.