I’m fixing to buy a kayak this Christmas, so I started looking into electronics. It seems like there’s a lot more to it than I initially thought. I understand what side imaging is, but what’s the difference between sonar, down imaging, CHIRP, and clear view (if there’s nothing else I’m missing)? From what I read on the internet, they look the same. All of the features seem a bit redundant to me. Then again, I haven’t the slightest clue where to start.
 

What should I look for? I’m mostly going to use my kayak to target crappie and offshore smallmouth. I might also use it for stripers in the bay.

First - each type has it's own active area. 2-D Chirp transmits/receives in a cone...the Yellow or Red area depending on frequency...so any 'blips' that appear could be in front, behind, to the left or to the right of you. DownScan (Garmin calls it ClearVu) is the Green line below...think of it like a slice through the cone...a blip could be to your right or left, but not in front or behind. SideScan is the most accurate of the three...Blue arcs...as it will show you if the blip is to the right or left.

Second - DownScan and SideScan show more detail...what looks to be a hump on 2-D might show up as a downed tree on DS or SS...you'll see the individual branches.

this is what a tree looks like on down scan

side scan looks the same but you dont have to be over it

on 2d it'll look like a blob instead

chirp is better quality 2d

 

Between 500-600 the 7" helix G3 with DI and SI is a great price. It's the older model but I don't think any of the g4 model changes are that useful anyway. Can get a g4 about that price new on ebay as well. I have this one, and I like it. I'm upgrading to get livescope, but otherwise have no issues with it at all. 

 

However, it can be a little overwhelming. You might get something like a standard helix 5 for $200 and learn the 2d first. Same deal with ebay, there a lot of people selling what they took off when they upgraded. 

 

Basically decide if you want to buy a starter unit and learn and then upgrade when you figure out what you care about, or bite the bullet and just buy once. There are a bunch of kayak anglers on here with electronics that can probably tell you about what they like. 

 

CHIRP isn't going to matter in a kayak unless you're fishing in 1000fow. Learning how to read sonar before you buy it should be your main goal. PLENTY of instructional videos on youtube. What you need to learn is "history" on the graph. Using 2D or DI, the rightest part of your monitor is the most recent ping(history). On SI, the top of the monitor is the most recent ping. Everything else is history. 

 

A sonar will only show a current image as something passes thru the beam. That means the vessel is moving and it shows what the vessel has passed over the beam or, the vessel is stationary and it shows and object that has passed thru the beam.

 

When using 2D the return is "harder" the closer it is to the center of the cone and "weaker" the further it is from the center of the cone.

 

In the example that @MN Fisher posted. The 75* cone at 455kHz. Lets say you have red set up as a hard return and yellow as a weak return. The red return is going to be something that passed directly under the boat. Any return that comes back as orange to yellow will be a return towards the side of the cone (vessel) or as an "outside" return. 

 

DI doesn't really differentiate between a hard and soft return and just shows what's going on under the boat. In the pic that @txchaser posted, in real time, you're already fishing in 75fow. The shelf,  ledge and trees are history.