We promote BioBase as an automated “easy-button” solution for creating aquatic maps, but unfortunately, mobile acoustic data collection is not something you can push a button and forget about and expect perfect results. Like using most other sophisticated instrumentation, users need to monitor that the instruments are performing as expected and sometimes make adjustments if they aren’t.
As such, we often stress the importance of monitoring your sonar and GPS display while logging sonar making sure you get a clear view of bottom with a continuous digital depth reading (Figure 1). If you can’t see a digital depth reading on your screen, add it (here’s how). And, add a depth line to your Sonar Screen in the Sonar View menu. If you’re a first timer not familiar with sonar of “fish finders” you should spend some time familiarizing yourself visually interpreting a sonar display prior to mapping “for real.”
Mapping Extremely Shallow Water: Tricks for a Tricky Environment
Areas of waterbodies less than 2 ft (< 0.75 m), are difficult to characterize with acoustics. Target separation between the bottom and the face of the transducer is extremely small and these environments are very acoustically noisy due to wind mixing. Accordingly, by default BioBase requires a minimum depth of 2.4 ft (0.76 m) to create vegetation and bottom hardness outputs. Reading depth alone is not as difficult and you may find your Lowrance unit providing reliable depths as shallow as 1 ft (0.3 m). But, as stated earlier, this is a tricky environment and the acoustic signal can easily be lost and difficult to recover, especially in Auto Range.
Alternative 1: Fix the Range (Shallow Water Only)
Fixing the Sonar Range to 5 ft in very shallow waters can be a tool to establish a known zone where the sonar should search for a bottom signal (Figure 3). This may ensure a more consistent bottom lock. But, Range should be reset to Auto if mapping in variable or deep waters to ensure the 3200 bytes of data are in the optimal range for bottom typing. Never change range during logging or it could corrupt the .sl2/.sl3 file.
Alternative 2: Use a Kayak