Learning to use 998c

I have spent several hours on the water and several more hours on the internet learning to use the 998c.

I am still having some issues which I know are my fault and not the machine.

The first is I am having a hard time in side scan mode determining the size of brushpiles logs etc that I see on the screen. I have decreased the range down to 50 feet on each side and i am having a hard time getting a feel if what I am looking at is large enough to fish or a small stump.

I have played with the settings and am running my scroll speed close to boat speed, I have played with the sensitivity and other settings.

The next issue is after marking brush etc. with the cursor in side imaging I am going to the split screen with chart and down imaging and still not confident that I am back over the object i marked. How accurate is the gps and is there some built in inaccuracy or is it affected by satellite reception etc?

I am sure a lot of this comes with experience but it is very frustrating.

Any advice or pointers will be appreciated!!!

You have already mentioned good starting points for settings.....

Chart speed to match boat speed....sensitivity to brighten or darken screen....side view out 2 to 3 times the water depth...

Now, when you mark structure on the SI....try to place the cursor and mark the point where the structure attaches to the lake bottom for the best accuracy....

1 tip I use when trying to "refind" structure (after marking) is to use the split screen SI/Chart...as you approach the structure watching the chart view...zoom in as you get closer to the WP....

Even then...It is very possible to miss going directly over it to show on the 2d.....this is where the SI comes in....the structure will show on the SI view either left or right of where you "thought " it was...giving you a better idea of where the structure actually is in relation to the WP you are seeing on the chart view..then switch to 2d/Chart to hone in on it...

After you are able to get close enough for the structure to show on the 2d...you may want to "remark" the structure with a new WP and delete the old one....

Inaccuracies in general public usable GPS are close..but sometimes not close enough when trying to "refind" already marked structure....

Trial and error will help you learn how big a brushpile is that shows on the SI screen...just remember that the farther out you have the side view reaching will make the image even smaller as the unit has to squeeze all that bottom coverage data into the same size screen....

Experiment with noticing how big a brushpile is on the 2d in relation to how that same brushpile is showing on the SI screen...I've generally noticed that a brushpile image on the SI screen is approximately 1/4 the size of the same brushpile image on the 2d screen...

Rickie

rnvinc,

Thanks for the tips. Do you prefer traditional 2d over downimaging for refinding marked spots?

DI vs 2d is a very opinionated discussion with these units.....

Some find DI as a replacement for 2d.....

Some find DI as an additional tool along with 2d...

Learn to understand the shape of the different sonar beam here...http://www.crappie.com/crappie/fishi...am-shapes.html ...

Use the info in how to best utilize that sonar beam shape for the type of fishing that you do....remembering that it doesn't matter if that object is under your boat...if that object is not in that sonar beam shape..it's not going to show on your screen....

Also remember that the DI image in the 1100, 900, 800, 700 series units is derived from the SI crystals in the xducer...(they do not have dedicated DI crystals like the newer 500 series DI units)....

Myself..in my 1197...I do not use the DI but very little....I feel the 2d is more sensitive to picking up the weaker returns....because of the lack of dedicated DI crystals in the xducer...

So, to answer your question...

I first search for wp's using split screen SI/ Chart.....

Then once I see the brush on my SI.....

I use the 2d/Chart to "refind' my WP's ......and for the following two reasons....
1. The cone shape of the 2d will pick up the brushpile in front of my boat before my boat gets to it...(The DI will only pick it up when the boat is actually on top of or to the side of the brush)
2. I feel the DI sensitivity in my 1197 is not as good at picking up weaker returns than 2d (because my 1197 doesn't have the dedicated crystals in the xducer)....

Rickie

Thanks. Excellent information. I really appreciate the help.

Thanks mvinc, very informative.......Thumbs UpThumbs Up

You can tell how large structure is by scaling it on the si screen. If your set to 50 ft range each side and the structure occupies approx 1/5 of that side of the screen then the structure is approx 10 ft wide. When I mark a spot and then go to fish it here's what I do. I approach the waypoint on the chart screen and when I think I'm there I drop a buoy. I then take a KY rig with a 1oz weight and start probing around the buoy until I feel the weight bouncing off the structure, then I know exactly where it is.

Another thing to consider when looking at GPS accuracy doesnt even have to do with the GPS itself, but with where your antenna is mounted. I used to notice my Waypoints were never that accurate then I realized I had my GPS antenna mounted on my console next to my unit which is about 10ft away from where my tranducer is. so I am automatically putting 10FT of error between what the image is showing and where the waypoint is actually marked.

Quote:

---

Originally Posted by jsplinter

Another thing to consider when looking at GPS accuracy doesnt even have to do with the GPS itself, but with where your antenna is mounted. I used to notice my Waypoints were never that accurate then I realized I had my GPS antenna mounted on my console next to my unit which is about 10ft away from where my tranducer is. so I am automatically putting 10FT of error between what the image is showing and where the waypoint is actually marked.

---

Great point.

I found that to be true. This spring i had my antenna moved to the back corner and just above the transducer of my 997csi unit. The previous spots i had marked, had to be re-marked as they were quite a bit off from the previous mark. Had my antenna up near the front last year and i have a 16 1/2ft boat. Marks were over 10ft off on all the old spots. Thats from the console. I have a seperate setup on the bow.