Chart speed and "time lags"

[Ratherbfishing]

Theoretically, I understand the concept and/or desireability of chart speeds (or maybe I don't)  but if you slow down the chart screen on a fish finder, does that not ALSO mean you are NEVER going to see, in real time, what is going on under your boat.  AND, the longer you use a slower chart speed, won't that just make the "time lag" that much longer?  I mean, after a while, wouldn't what is on the screen be TOTALLY different than what is actually under or around you?  Am I missing something here?

[Kevin22]

Slowing the chart speed actually slows the transmitting of the sonar signals, not just the screen. If you listen to your transducer when playing with the scroll speed you will hear it go from tick tick tick tick to tick....tick....tick...tick. So it slows everything down so there is no backlog. 

Hope that makes sense! 

[eddallen]

I'm not sure what you are saying, but, 'real-time' is ONLY as it starts to appear on the screen. All other is History. The only times I slow down the chart speed is when I am fishing dead-stopped. Even when I am only trolling at .75 mph I have the chart speed on Normal. When dead-stopped (in a slip) the bottom never changes because you are not moving. Technically, slowing down the screen speed changes the interpretation of what the firmware draws on the screen.

[Ratherbfishing]

33 minutes ago, Kevin22 said:

Slowing the chart speed actually slows the transmitting of the sonar signals, not just the screen. If you listen to your transducer when playing with the scroll speed you will hear it go from tick tick tick tick to tick....tick....tick...tick. So it slows everything down so there is no backlog. 

Hope that makes sense! 

I think so.  So, at a reallllly slow chart speed, won't it be a bit "jerky"?

[Kevin22]

Cheaper ones will, better ones with higher processors will be more fluid. 

I've never used mine less than "normal" and most of the time it is on fastest. I want to know whats going on below me NOW (fish), especially when moving slowly. When sitting still its always on fastest so I can see if there is a fish below me. I don't care to mark structure, that is what the DSI is for. Sonar is for fish, DSI for structure on my boat. 

[eddallen]

4 hours ago, Ratherbfishing said:

..., after a while, wouldn't what is on the screen be TOTALLY different than what is actually under or around you?  Am I missing something here?

If you are looking right at your sonar, the leading edge (right edge) of the screen is NOW, and everything LEFT of that point is 'history'. Unless you are not moving. So, when you see a fish in 'the middle' of your screen, it is not actually under or around your immediate location 'at that time'.

[WRB]

What may be missing is the basic concept of how your sonar unit works and what the display is showing. Everything printed on the screen is a history of what the sonar has returned. The only real time display is shown as a straight line flasher on the first 1/4" of the far right edge of the screen, top line is water surface and bottom lines indicate the lake bottom, everything in between are sonar returns within the cone angle of the transducer. If the transducer is mounted on one in the back of the boat everything shown is already in your wake...even the real time returns!

Chart speed is simply the speed the screen scrolls the display.

Ping rate determines how fast the transducer pulses.

Tom

 

[Neil McCauley]

I put mine on fastest possible. I want to know what's going on underneath by the second and when I'm moving don't want to miss anything. Why do anything other than fast chart speed? So you can look at a longer term record of it on your screen? I don't really care what happened 10 seconds ago or what I passed 10 yards ago. I want to know what's underneath at the moment, or have a decent graphical representation of the bottom and the things I pass over at 3-5mph.