Navionics Web App Symbol Help

[Avalonjohn44]

I've been looking around at the Navionics site planning out my next few trips and cannot identify a common feature that I keep running across all over the lake (Lake Anna in VA).

All over the lake there are dotted lines of plus symbols: ++++++. I downloaded the US Chart Symbols and Terms guide and I can't match the symbols up. The closest I can guess is gravel beds, but I'm far from certain.  Below is a screen shot of what is puzzling me.  Sorry if this is a completely obvious question. I'm a total noob on the Navionics so far...

 

 

[gulfcaptain]

Looking on Noaa's ChartNo1pdf, I would say that is likely a rock area that is a hazard to navigation.  The definition given is "dangerous underwater rock of uncertain depth."  I'd say fish it, but don't run over the top of it.

[A-Jay]

I'd say @gulfcaptain has it right. 

ChartNo1 has it as  "Danger line: A danger line draws attention to a danger which would not stand out clearly enough if represented solely by its symbol (e.g. isolated rock) or delimits an area containing numerous dangers, through which it is unsafe to navigate"

 

Translated into "Bass Head" that may mean "Throw Squarebills & Jigs here with wreck less abandon".

A-Jay 

[Avalonjohn44]

That makes sense, but there are many other instances of the same +++++ lines in 35 to 50 feet of water,with no shallows nearby where the navigation wouldn't be at all hazardous.  The instance I happened to clip was in shallow water, but they are all over the place which was why I was thinking it indicated gravel beds rather than danger line. Here is another example in deep water:

 

 

 

[gulfcaptain]

Got me on the deeper depths without really looking at the chart as well as having a paper chart to reference and cross check.

[tigar]

Could the deep water danger be standing timber which would be under the surface? 

[Ohio Archer]

The Navionics app will tell you what it is. Put the ++++++ area in the center of the screen. Tap it once and the cross hairs will come up. Press the ? Symbol and the next screen should show "Obstruction" at the bottom. Select "Obstruction" and is will tell you what it is. Works that way on my iPhone. 

 

On your computer place the mouse inside the area you want to see and do the same thing.  They are not all obstructions but also restricted areas, i.e. "Information: elk creek boat access restricted to residents only".

[Avalonjohn44]

4 hours ago, Ohio Archer said:

The Navionics app will tell you what it is. Put the ++++++ area in the center of the screen. Tap it once and the cross hairs will come up. Press the ? Symbol and the next screen should show "Obstruction" at the bottom. Select "Obstruction" and is will tell you what it is. Works that way on my iPhone. 

 

On your computer place the mouse inside the area you want to see and do the same thing.  They are not all obstructions but also restricted areas, i.e. "Information: elk creek boat access restricted to residents only".

 

Yes, this is the first thing I tried, but it does not give any entry for these symbols...

[Ohio Archer]

2 hours ago, Avalonjohn44 said:

 

Yes, this is the first thing I tried, but it does not give any entry for these symbols...

Where on Lake Anna is this spot?  All the lakes I have that have these symbols give me a description of the obstacle.

 

 

[Avalonjohn44]

 

20 minutes ago, Ohio Archer said:

Where on Lake Anna is this spot?  All the lakes I have that have these symbols give me a description of the obstacle.

 

Directly cross the lake from Anna Point Marina...  After re-reading your post, I went thru a few of the line and double clicked on several different areas along the line. On most portions of the +++ areas double clicking only lists the county, state and depth. On a few of the individual plus symbols it does say underwater obstruction, snag/stump (Stump field?).  Even on the deeper ones. I am now guessing the shallow ones like my first screen grab are for careful navigation, the super deep ones at 35+ feet are for being careful during anchoring...

[Ohio Archer]

Looking at your first picture I would say they clear cut that point but left the stumps.  Yeah, I wouldn't be running across it unless I had graphed it extensively.  If the stumps are still there it may be an excellent place to fish. 

[J Francho]

An underwater obstruction at greater depth is probably warning against anchoring due to pipes, power lines, or just snaggy territory.  Actual obstructions will get their own icons, like stumps, houses, roadbeds, etc.  A good example of this would be Santee Cooper, in SC.  Lake Marion has plenty timber, just below the water's surface, in deep water.  Running lanes are clearly marked, as are the stump hazards.  Just to the south, in shallow Lake Moultrie, there are roads, houses, and stumps.  Locals love to watch out of towners tear up their LU, while they run the known safe areas.  Took me a couple days of trolling around before I'd even get on plane in that place.  Maps help, but they're not perfect.  Pay attention, and mark safe boating trails to follow.

[Wayne P.]

I have a few of the old paper maps of Lake Anna. Those areas are designated as stumps.

 

Navionics has been adding those notes back to their maps after they lost the rights to publish those map details around 2009.

[Avalonjohn44]

That's good to know. I wonder why they just didn't use the stump symbol or, as I've seen on different areas of that map, just the words 'stump field'.

[Wayne P.]

Additionally the Humminbird units with ContourXD background mapping have most of the stump areas marked since ContourXD is the 2006 Navionics Hotmaps Premium map.

[Ru5tyNut5]

Could this also be lilly pads?  when I click on the lines on a local lake it just says obstruction and when I look at the lake from google maps the areas outlined all are full of pads.  if that's the case it make them easy to navigate.