Sonar VS downscan

[RJMOEN]

Looking at a Lowrance Mark 4 DSI/Gps or an Elite 4 Sonar/Gps color or an Elite 4 DSI/Gps color.... I think I understand what DSI is...gives you much better picture of the bottom... But does it give the same image of the water column that Im used to like on sonar(but better pic)? Trying to decide between the three...leaning towards the Mark 4 as the big C store has it cheap with 20% back in C-store points... ANY opinions or thoughts on the matter would be great. THanks

[BartmanMN]

Sonar will show you a blob of something on the bottom, down scan will show you that blob is a brush pile. Down scan is good at displaying detailed structure, where sonar is better at displaying fish arches. Both with show you different bottom composition once you learn how to read them

[RJMOEN]

I understand downscan is awesome at bottom detail but will i still get detail of suspended fish?

[Wish-I-Were-Fishn]

Just run it split screen mode and you will see both views.

[eelpout50]

Keep in mind that the lowrance dsi units are dsi only. They won't give you a traditional read out. The h birds at the same price point gives you the option of both views.

[Kyhl]

Things to consider.

One difference with the HDS is the DS is a straight line directly under the boat where the traditional sonar is a cone that covers a large cone under the boat. I would think that the DSI's would work the same way but would like to hear someone confirm.

I run the HDS in split screen and watch both the DS and the sonar. Sometimes things will show up on the sonar that are not right under the boat, in the cone, but they may not show up on the DS. (I will see these on side imaging but that's not an option to the OP).

The other difference is that I see things faster in sonar. Things will show up in the traditional sonar a second or two before I see them on the DS or SI.

If this is for a main finder then I would try to get something that shows both DS and traditional sonar.

[toddb]

Downscan cone angle will be smaller due to the higher frequency transducer employed. Lower frequency = more beam spread(higher cone angle). Transducer size also effects cone angle, but with all things considered(same transducer element size) a 200 kHz xducer will have close to 4 times the cone angle of an 800 kHz.

With the narrower cone angle of the higher frequency xducer the target will not enter the cone and be imaged as fast as the wider cone of the low frequency xducer. This, along with processing time may explain why they seem out of sync in split screen.

The downscan really shines when targets are tight to the bottom. The higher frequency allows better

resolution (buzzword "target separation"). When imaged, the responses from the higher frequency xducer provided a more detailed image. This is due to the fact that the unit is imaging the returns based on a programmed beam angle. When lower frequencies are used the time of flight from the returns near the edge of the cone have a longer water path than those near the center of the cone. The unit does not know these returns may be from the 10degree angle but will still image them at a 0 degree angle. With those added returns, targets will not be discernible from bottom/ structure due to the addition of bottom returns which are at the same water path. With higher frequencies the returns are at water paths close to the central beam angle allowing a more defined image.