Humminbird Side Imaging Forums

Side Imaging Forums => 997c SI, 998c SI & 999ci HD SI => Topic started by: fishbone on April 12, 2013, 03:56:42 PM

Title: Down image
Post by: fishbone on April 12, 2013, 03:56:42 PM

What is the differance between "sonar" and Down Image" views? Is it the source of the display?

Title: Re: Down image
Post by: rnvinc on April 13, 2013, 09:30:04 AM

Sonar is a general term for technology using sound pulses (pings) sent thru the water column to bounce off of objects in the water and then returned to the unit to show on the display as "Echo returns"...

There are 3 technologies in the general scope of Sonar...

This is 2d Sonar..(2dimensional)..it is created by sending many successive sound pulses (pings) thru the water column in a "cone shape"...and creates a "cartoon-like" display image of echo returns detected under the transducer in that "cone shape"...
(http://i477.photobucket.com/albums/rr134/rnvinc/HB/dualbeamPLUS_screenshots1.jpg)

This is DI (Down Imaging)...it is created by sending many successive sound pulses (pings) thru the water column in a "thin slice" shape...and creates a "picture-like" display image of echo returns detected under the transducer in that "thin slice" shape...
(http://i477.photobucket.com/albums/rr134/rnvinc/HB/SwitchFire_DI2.jpg)

The 3rd Sonar technology is SI (Side Imaging)... Of which you did not ask so we will leave that for a different discussion...

Rickie

Title: Re: Down image
Post by: fishbone on April 13, 2013, 09:56:28 AM

Great explanation, Rickie. Thanks

As I understand what you are indicating;     my 998SI is shooting an SI beam(s), two different freq cone beams and a side image shaped beam straight down for the "down image" display.

Or, is the electronics taking a "slice" reading from the cone beams?

Title: Re: Down image
Post by: Humminbird_Greg on April 15, 2013, 01:03:52 PM

fishbone,
Your 998c Si unit is shooting a 2D sonar beam (possibly two if you have the Beam Select set to 200/83kHz) and it is shooting two Si sonar beams.  The Si sonar beams are very wide and cover the area from the surface at the left side of the boat to all the way under and around the water to the surface on the right side of the boat.  The 998c Si unit uses the sonar information from both the left and right Si sonar beams to generate the Di sonar that you see on the screen.