Thread: Long and Maybe a bit OT, Santee navigation

Originally Posted by 91tiger

Google “Navionics Web App”. It will allow you to view Navioncs lake mapping on your computer or phone without paying a fee. It obviously does not show stumps but it does clearly show the boating lane exiting the canal and other marked boating lanes. Good thing to study before you go. You can also get the Navionics app for your phone and use it on the water to help with navigation.

Also, it’s not a great idea to idle around with the motor looking for boating obstacles. You will find them with the motor, just like you experienced. Raise your trolling motor way up and ease in and check if you must.

Yeah I got the Navionics app for a while now. I can see the usefulness of it, particularly following channels as you mention. It's also a great compliment to the new Garmin and checking contours, creek channels, points, etc. in most all the lakes around.
And to clarify, no, I wouldn't go looking for specific stumps and rocks with the main motor down. If there's something specific like the Santee rock piles I'd ease up with the trolling motor.

Originally Posted by Bigtrout

Yeah I got the Navionics app for a while now. I can see the usefulness of it, particularly following channels as you mention. It's also a great compliment to the new Garmin and checking contours, creek channels, points, etc. in most all the lakes around.
And to clarify, no, I wouldn't go looking for specific stumps and rocks with the main motor down. If there's something specific like the Santee rock piles I'd ease up with the trolling motor.

I've never used mapping on the Garmin but there does seem to be a push by the depthfinder manufacturers to provide much more accurate mapping. Lowrance came out with their CMap card which my understanding is they sent out teams to survey the lakes and create ultra high resolution mapping. I've never used it for Santee because I haven't fished there in years but it is unreal how good it is for Hartwell and Murray. But unfortunately it isn't accurate at all for Greenwood, Navionics is way more accurate there. But it may be worth talking to the local bass guys at Santee and see which card they like best for there. If you see one with three 12 inch screens at his console that's probably the one to ask. The bass guy I know that fishes Santee regularly really likes the Lake Master chip form Hummingbird but I don't think he has tried the Lowrance Chip there.

I have the Garmin ECHOMAP UHD 93sv. At Bass Pro I asked the guy about it. It comes with Garmins LakeVU maps of pretty much most inland lakes, and the GT54 transducer. I asked him why one was on sale and the other was almost twice as much. The one on sale is about 5 years old, discontinued to be replaced with a newer unit, and thus marked down. The newer unit has the newest GT56 transducer and Navionics. I asked about the difference between LakeVu and Navionics. He said LakeVu was Garmin's own lake mapping but that Garmin had bought Navionics and added it to their new units. I asked if one mapping had a definite advantage over the other. His response was, "Nah, not really". I decided to save the money and get the older unit and figure it is adequate for my needs.
And I figure the best one can expect at Santee anyway, is using mapping to mark the established channels. Well, and like any other lake, channels, dropoffs, humps, or other underwater features in the deeper water.

I used my new Garmin on Greenwood this week, rather extensively just to learn the basics. First it is awesome. The only thing I need to work on is tweaking the color/contrast/brightness to see the objects on SideView. I see the shadows clearly but have a difficult time seeing what is casting the shadow.

The other thing I noticed specific to mapping. I was looking at a place on Greenwood where a side creek channel joins the main channel. The Navionics app on my phone, and the mapping in my unit showed the same bottom contour, however, they did not show me in the same position on the lake. Close, but not the same. Cannot say for sure which one was off but could have been one or the other was updating GPS signal at the time. I'll check that again to see if it's consistent or just happened at that point.

Originally Posted by Bigtrout

The other thing I noticed specific to mapping. I was looking at a place on Greenwood where a side creek channel joins the main channel. The Navionics app on my phone, and the mapping in my unit showed the same bottom contour, however, they did not show me in the same position on the lake. Close, but not the same. Cannot say for sure which one was off but could have been one or the other was updating GPS signal at the time. I'll check that again to see if it's consistent or just happened at that point.

The few times I have used my phone app, the GPS position was not super accurate. You wouldn't want to use it to run a narrow stump lined channel like in the upper end of Clarks Hill.

Originally Posted by 91tiger

The few times I have used my phone app, the GPS position was not super accurate. You wouldn't want to use it to run a narrow stump lined channel like in the upper end of Clarks Hill.

Good to know. I have noticed on the phone app, if I'm trying to hit a specific point, the position icon sometimes stops moving then jumps or turns. Kinda glitchy like. I assumed that was the phone GPS updating the signal. May be the cause of what you speak of.

Be careful with ANY mapping, especially before you verify it, but I know of one lake in SC that Cmaps shows being 20-24ft deep, that's actually several acres of flats with stumps in it, that can even be seen via google earth/maps. I've alerted them about a year ago, but no change. Not that Im aware of anyway. I don't have a subscription to it, but use their web ap, and it's been down a while since their security breach a few weeks ago.

I may be totally off base here but I believe most maps that show lake bottom contour are based on topographic maps. So that would mean using topographic maps before the creation of the lake, since topographic maps were made using aerial photos, which were updated only after a period of years, and wouldn't detect lake bottom contours after creation of the lake. Something could have changed drastically between the last update and closing the dam to flood land. Siltation and erosion could be a huge factor in lake bottom changes.

I don't know if satellite imagery is used today, or if some technology exists that DOES actually map the bottom, like sonar soundings, etc. I'd have a tendency to trust Navionics most, since it IS specific to water navigation. That said, we used to navigate lakes BEFORE we had any type of mapping software, just using our brains. Which, at the end of the day, is our first and last line of defense.

I see many a boats running at speed in 5-6 feet of water. I always figured they just didnt know how shallow it really is. NOT what I wanna do though!Santee can be EXTREMELY dangerous to navigate if you dont know the lake.