Humminbird Side Imaging Forums
General => General Discussion => Topic started by: Deltaden on May 13, 2010, 09:25:45 AM
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I"m learning more every time I use my HB 898. but I still consider myself a novice and hope this is not a question that is way out of place or has been explained elsewhere. If my boat was "dead in the water" and sitting atop an object, like a sunken boat or something like that, why does it show up once on the screen then scrolls away. Would not the "ping" of the sonar refresh the image and keep the object on the screen? I have a hard time understanding the need for the scroll function of a fish locator.
Thanks anyone.
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I know this seems like a simple issue, but understanding how the SI works is the key. While the unit is on or lets say actively pinging, in order for it to show new data, it has to scroll the old data off the screen for each new ping from the transducer. So for Side Imaging to work the way it is supposed to, the boat has to be moving. Once you stop, the transducer is now pinging the same spot in the water over and over, and the image is going to look like lines at best.
Basically, the way Side Imaging works is to take thin slices (or pings) of an object or the bottom and display them on the screen. Each time the transducer pings (slices) it displays this slice to the screen at the top and moves the older slices down. As you move along, these slices are changing and you get the image of the wreck on your screen. Again, if you just take the same slice over and over (not moving) you are not going to have the pretty picture of the wreck.
If you are stopped over a wreck, I would suggest turning to a 2d view so you can see fish when they pass under your transducer!
Here is a wikipedia article on Side Scan Sonar. http://en.wikipedia.org/wiki/Side-scan_sonar (http://en.wikipedia.org/wiki/Side-scan_sonar)
If you ever get to the library, check out the book Sound Underwater Images (http://www.amazon.com/Sound-Underwater-Images-Generation-Interpretation/dp/0936972149/ref=sr_1_1?ie=UTF8&s=books&qid=1273760462&sr=1-1). It is considered the Bible on Side Scan Sonar.
I hope that helps a little.
Robert
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Unlike a TV or computer monitor the whole screen is not refreshed. Only the top line of pixles is refreshed with each ping and each line is moved down one row until it scrolls off the screen. One of these days we will have full screen refresh and the fish really will not have a chance.
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The last post by ETnNC hit the nail on the head for me. I never thought of it "that way".
Thanks to all.