Do some plotters have a depth alarm?

[Ships_Cat]

Re: Ok - lets look at the problem ...

Even in Vector charting sounding data is not a separate layer to work with - so how will program extract that info

I will have to have a play next time on the boat to see what happens in real life (no publically released S-57 cells for our local waters so haven't tried this bit for a long time but I can check as ECS can act as a simulator using vectors for other waters) but the ECS I use definitely does (with S-57 charts) things like use different colours for depths shallower than those nominated by the user, will cross hatch shallow area if shallower than those nominated by the user, draws safety contours according to depths set by the user, etc.

For the look ahead shallow warning it is described as "The Shallow Depth Area Ahead warning occurs when the vessel is located in or about to enter, within the vessel's Look Ahead time, a shallow area. Whether or not an area is defined as shallow depends on the Safe Depth (see VESSEL / Characteristics / Safe Depth of the ship relative to the depth of the water." The safe depth is that entered by the user into the table of vessel characteristics.

How it does it from the data in the chart file I have no idea - as I say I will run the simulator on a S-57 chart next time I get a chance.

John

 

[Guest]

CMapECS had a limited ability to ...

So maybe someone is developing that - but as far as I am aware - it's only Vector that could do it ... raster couldn't.

It's interesting that the Lowrance - if you set a route through suspect waters - it can advise against ... so maybe it's using same ability ?

 

[steverow]

Re: Ok - lets look at the problem ...

In many ways what we are looking at here is the Holy Grail of chartplotting and probably the next big leap forward.
The ability to know your depth at any time at any place and to have that depth displayed on the chart in real time...ie constantly changing depths displayed.
In theory it's possible now with tidal calcs added or subtracted from known spot soundings, but as Nigel has alluded to it's down to the way that vector charts are layered that is the problem.
I dont think that real time depths are very far away though on top end ECDIS systems, if someone comes up with the cartography system to enable it.

Steve.

 

[Malcb]

PC Planner, that comes with C-Map charts does have an anti gounding alarm.

However, would you really rely on the accuracy of a chart, plus the accuracy of the SatNav system to detrmine the depth under your keel. I know I wouldn't.

Today I ghosted my way up to Dell Quay, with a depth gauge showing less than 1 meter below the keel, jumping from 0.5 to 1.2 metres at times. Surely no chart is accurate enough, or up to date enough, (depths change) to be relied on wholly for navigation in shallow waters as far as depth is concerned.

The facility given on C-Map planner to give an alarm if you plot a course over shallow water (or land) is there to prevent major planning blunders like planning a course from Chichester Bar to Cowes and failing to prepare intermediate waypoints.

 

[Ships_Cat]

Re: CMapECS had a limited ability to ...

So maybe someone is developing that

I think if you read my post you will see that it is already developed. In fact I have been using that ECS for 3 or 4 years now.

it's only Vector that could do it ... raster couldn't

Yes, that is what I said, many times /forums/images/graemlins/smile.gif, and included many references in my post qualifying it was with S-57 charts /forums/images/graemlins/smile.gif.

You must read properly what others post /forums/images/graemlins/smile.gif.

John