Scroll Speed - 2D Sonar
Written by Adam Broughton.
The scroll speed setting on most sonar units controls the speed of BOTH the 2D sonar and sonar imaging screens. However, each has totally different use on the water. So depending on which you're using (2D or imaging), you'll need to set your scroll speed accordingly.
Here is what you need to know about setting scroll speed on traditional 2D sonar screens:
The sonar information you see on your display is history. It isn't what is there now, it is what was there a few seconds ago. For example, if you see a classic fish arch on your display, that fish WAS, but IS NO LONGER under your boat. In most types of fishing, it is good to know that you passed over a fish. The history is useful to us and we should manage it properly. Note: scroll speed is sometimes called "chart speed" --same thing.
Information that is closer to the right is "fresher" history than information more to the left on the screen. Taken to an extreme, ice fishermen up north only care about what is happening at that moment. They don't care about history. The want to know when a fish is under the hole, and at what depth it is located. So those flashers that went away in the 1980's have made a (huge) comeback with ice fishermen. They are exceptionally popular because they simply show instantaneous sonar.
So you can think of scroll speed on your 2D sonar as controlling how much history you see over time. Slower scroll speeds cram more history onto the screen, and faster scroll speeds roll it off and show less. Functionally, on the water, this is the only factor that you need to consider when setting your 2D sonar's display scroll speed.
Under what conditions would you want to show more history and which less? The answer is how much time you spend looking at the display. If you look at it frequently, speed it up. If you glance now and again, slow it down. For example, if you are casting to visible structure, looking up and away from the boat, you probably want to slow the scroll speed to a crawl. It could be many seconds, if not minutes before you glance down and check it again. So slow it down and put more data on the display.
You would want to speed up the scroll speed if you are looking at the display frequently. A extreme case might be vertical fishing, like drop-shot fishing or jigging a spoon. When vertical fishing you are literally watching the display constantly, like an ice fisherman. So speed it up. If you are watching the display, turn the speed up all the way up.
You might have noticed an option for "RTS" in your menu. This acronym stands for "Real Time Sonar" and is the sonar intensity bar on the right side of the screen. You might want this ON when vertical fishing as it will help your eye focus on the most current data. Turn it OFF when you want to show more history so that it isn't taking up valuable real estate on the screen.