Read outward from the center
We like a good sonar screenshot as much as anybody. But a bright blob labeled 'probably a giant' is still a bright blob. Learn its shape, mark its location and go fish it. The center of a side-imaging screen represents the boat's path, with left and right returns displayed on their respective sides. The dark water-column area separates the track from the bottom image. A bright object can be rock, wood or another strong reflector. Its shadow is often the better clue: a raised object blocks sound behind it, leaving a dark area that helps reveal its shape and height.
Drive a line the image can explain
Idle straight and hold a reasonably steady speed. Sharp turns can stretch one side and compress the other because the transducer is sweeping through the scene unevenly. Start with a moderate range around a known feature, then narrow it when objects are too small to recognize. More range covers more water but assigns fewer screen pixels to each stump or fish.
Use shadows to choose what deserves another pass
A long branching return with a branching shadow may be a fallen tree. An isolated bright patch without clear shape may need a different approach angle. Compare the return and shadow together instead of calling every bright dot a bass. If the feature matters, pass from another direction. The new angle can separate objects that overlapped in the first image.
Save the target while it is in history
Place the sonar cursor on the object and use the unit's supported waypoint command. Do not substitute a current-boat-position mark when the object is off to one side. After marking, move away and return on a controlled approach to check the location. Use Down Imaging or conventional sonar when a crossing pass will help determine whether the cover rises above the bottom.
Choose a cast that uses the information
A tree extending off a bank can be approached along its outside edge before pitching into the branches. A hard-bottom patch beside softer bottom can be fished along the transition. The image has helped you identify geometry; it has not guaranteed fish. Fish the most accessible edge, note the bite location and move on if the feature produces neither useful returns nor a response.
Fix a bad side before changing the whole picture
If one side is consistently weak, inspect the transducer's line of sight for a motor, hull feature or other obstruction according to the installation guide. If both sides become poor at speed, consider water flow. Use chart-speed adjustments to improve proportions during a steady pass, not to disguise a constantly turning track.
Put it into practice
- Hold a straight course while building the image.
- Read the shadow together with the bright return.
- Use the cursor to mark off-track structure.