Chartplotter - can they do this?

[Alpha22]

I've only ever used Navionics on an iPad as a plotter so my knowledge is limited. Other than that I have always used a Yeoman... (I know, AND I'm under 45!!)

It strikes me that it would not be difficult to get a chartplotter to combine the vector chart information about depths and tidal predictions to produce an actual (although "forecast") depth and display this 'live'.

So if your plotter shows 10 meters of water, you are actually in 10 meters of water...... (give or take a bit) rather than showing LAT.

Routes could be plotted with start times and expected speeds so the depths could show the actual depth at the time you will be crossing that point.......

Dangerous??? Useful??? or do they already do this??

 

[prv]

It does seem a mildly useful function, but I've not heard of one doing this.

(And good call on the Yeoman )

Pete

 

[omega2]

use an admiralty chart, it's all on there

 

[Alpha22]

use an admiralty chart, it's all on there

Did you read the original post?? If so, I'm sorry, I don't understand your response. Could you explain how the Admiralty chart can show the actual live depth on a piece of paper?

 

[PilotWolf]

Transas certainly does tidal heights at given points along with tidal flow speed and direction in its' NaviSailor program but that is designed (and priced!) for big ships. But it is predictions just like the tide tables.

W.

 

[maby]

There would be a lot of interpolation involved - charts include some spot depths but the bulk of the data is contour lines at 5m depth intervals. It would certainly be possible to calculate estimates, but that is all they would be and I guess the plotter manufacturers might be concerned at the possibility of being sued because someone has put too much faith in the estimate and run aground. Also don't forget that weather conditions can have a big effect on tidal heights and the plotter will not know about them. Around the Thames estuary recently we have been seeing positive and negative tide heights of as must as 1.5m relative to predictions.

 

[omega2]

Did you read the original post?? If so, I'm sorry, I don't understand your response. Could you explain how the Admiralty chart can show the actual live depth on a piece of paper?

there are depth soundings all over the chart, and you should know if the tide is ebbing or flooding, also gives direction of flow in box at top left hand corner, before and after high water

 

[omega2]

There would be a lot of interpolation involved - charts include some spot depths but the bulk of the data is contour lines at 5m depth intervals. It would certainly be possible to calculate estimates, but that is all they would be and I guess the plotter manufacturers might be concerned at the possibility of being sued because someone has put too much faith in the estimate and run aground. Also don't forget that weather conditions can have a big effect on tidal heights and the plotter will not know about them. Around the Thames estuary recently we have been seeing positive and negative tide heights of as must as 1.5m relative to predictions.

+1 especially in the Thames Estuary.

 

[[70521]]

It strikes me that it would not be difficult to get a chartplotter to combine the vector chart information about depths and tidal predictions to produce an actual (although "forecast") depth and display this 'live'.

It is the tidal predictions that make this difficult, the prediction can be way out - think of the weather we are having and look at some of the actual tidal gauges on the Internet.

Drawing up the tidal curve for the day takes less than a min and a simple sum give you the depth pretty quickly and you can double check the maths.

 

[Gez]

I worry when people put too much faith in tide predictions, expecting accuracy down the odd cm.

Have a look at the National Oceanography Centre's (NOC's) real time tide gauge page, which shows predictions versus actual tides for a range of sites around the country:

http://www.ntslf.org/data/uk-network-real-time

Some strange weather effects lately. e.g. on 3rd Feb at Portsmouth, the midday high tide dropped 50cm in only half an hour (from observation).

Having said that, I think it would be useful to incorporate tide predictions into live navigation software - although I'm not sure how you'd deal with the usual "not to be used for navigation" disclaimer on tide predictions.

Gerry

P.S. I'm biased since I was involved with NOC's anyTide prediction app (as mentioned in Feb's MBY) ...