Depth finder chart speed??

[recke]

If some one could explain the chart speed to me I would really appreciate it. If you are sitting still in the water and the chart is moving, what is it doing relative to the bottom? Is it just running a loop of what is seen in the cone? Then when you are moving over the bottom slowly, what is happening regarding the picture that moves across the screen relative to what is moving by underwater. What if the boat is moving over the bottom faster than the speed of the chart -- or vise versa?? Confused. Thanks in advance.

 

[Drowned Rat]

Re: Depth finder chart speed??

Fisherman, the chart moving across the screen is showing the passage of time only. It doesn't represent distance or speed although some units have separate functions for this. When sitting still you are getting a "constantly updating" picture of what's underneath the boat. Same thing when moving, regardless of your speed.

 

[acc]

Re: Depth finder chart speed??

Wow....You need help......Too many questions....<br /><br />I'd suggest going to Lowrance or Eagle websites...Both have good sonar tutorials....<br /><br />Chart Speed relates to the repetition rate of the transmitted sonar pulses......A set of vertical pixels on your display represents that travel of that pulse of energy to the bottom surface and all of the echos from top to bottom. Chart speed does not relate to your movement relative to the bottom.

 

[Boatist]

Re: Depth finder chart speed??

Fisherman<br />The only thing that is under your boat is the right most row of pixels from top to bottom. after that echo comes back you move all the pixels to the left and send out another pluse and when the echo comes back you fill in the right most row again. Then you repeat the same thing. So what is under your boat is the right most row of pixel from top to bottom. Every thing left of that row is history or what was under your boat before.<br /><br />So your fishing at noon with the sun straight up and a fish near the bottom swims up and stops in the shade of your boat and where he stops he is in your transducers cone. What your will see is a line start on the right and move to the left at what ever depth the fish is at. When he moves on the line will clear on the right and then clear across the screen.<br /><br />Chart speed is just how fast you send out pulses. In general the higher the chart speed the eaiser it is to see fish arches, but what was under your boat will scroll off faster.<br /><br /> http://www.lowrance.com/Tutorials/Sonar/sonar_tutorial_01.asp

 

[imported_JD__]

Re: Depth finder chart speed??

fisherman42, <br />I don't know what type unit you have but if I increase the chart speed of my unit I am in actuality increasing the "ping" rate of my unit/transducer. If I were traveling at trolling speed a fish will be pinged several times allowing the unit to "paint" a complete picture but if I increase speed to let's say, 20-30 mph, fish that would normaly show up as a well defined arch now only appear as a blip on the screen because I am receiving fewer pings/returns per linear foot traveled. Increasing the chart speed will help compensate for the faster ground speed, to a point.

 

[rickdb1boat]

Re: Depth finder chart speed??

Don't know about you guys, but I always have my scroll rate on high. As was said, it will give you the most up to date info under the boat. But you have to keep a close eye on it...

 

[recke]

Re: Depth finder chart speed??

Thanks guys for the info. Now I get it.