Navionics vs others for tide depths
Discussion
I've seen several recommendations for Absolute Tides on some sailing forums.
If you're in the Thames estuary area and have internet access Harwich VTS publishes real time info on their website which you could use to extrapolate to the nearest secondary port to you or use that info and a chart to calculate the depth in your location. Could be other major ports offer the same.
Or simply do what I do anytime I need to know depth with a soft pencil, a 50p tide table and a set of these...

Both methods are equally valid IMO but as there's often little variation once you've taken current air pressure into account between predicted and actual depths pushing your luck between the two sets of numbers is seriously risky.
If you're in the Thames estuary area and have internet access Harwich VTS publishes real time info on their website which you could use to extrapolate to the nearest secondary port to you or use that info and a chart to calculate the depth in your location. Could be other major ports offer the same.
Or simply do what I do anytime I need to know depth with a soft pencil, a 50p tide table and a set of these...

Both methods are equally valid IMO but as there's often little variation once you've taken current air pressure into account between predicted and actual depths pushing your luck between the two sets of numbers is seriously risky.
Edited by Jaguar steve on Tuesday 31st August 08:15
Jaguar steve said:
I've seen several recommendations for Absolute Tides on some sailing forums.
If you're in the Thames estuary area and have internet access Harwich VTS publishes real time info on their website which you could use to extrapolate to the nearest secondary port to you or use that info and a chart to calculate the depth in your location. Could be other major ports offer the same.
Or simply do what I do anytime I need to know depth with a soft pencil, a 50p tide table and a set of these...

Both methods are equally valid IMO but as there's often little variation once you've taken current air pressure into account between predicted and actual depths pushing your luck between the two sets of numbers is seriously risky.
I suspect the OP is asking for the charts to show the 'actual' depths by taking the predicted tidal heights and adding them those normally displayed at chart datum.If you're in the Thames estuary area and have internet access Harwich VTS publishes real time info on their website which you could use to extrapolate to the nearest secondary port to you or use that info and a chart to calculate the depth in your location. Could be other major ports offer the same.
Or simply do what I do anytime I need to know depth with a soft pencil, a 50p tide table and a set of these...

Both methods are equally valid IMO but as there's often little variation once you've taken current air pressure into account between predicted and actual depths pushing your luck between the two sets of numbers is seriously risky.
Edited by Jaguar steve on Tuesday 31st August 08:15
Of course a better solution would be to take the reading from actual tide gauges, such as the one you mention, rather than using predictions but I'm still not convinced it is entirely a good idea.
L_G said:
Of course a better solution would be to take the reading from actual tide gauges, such as the one you mention, rather than using predictions but I'm still not convinced it is entirely a good idea.
As long as you have a decent safety factor you should avoid running aground. I am not surprised there is now "an app for that". lol
In my day we had to do it all from old fashioned paper tide tables and draw everything on the paper chart. Electronic charting software and tidal software was beginning to come of age but that was a back up and not to replace doing it "properly". The software was a very early version called "total tide" and to be fair to it, as long as you but decent data in it, the answers were correct.
I still remember the bane of having to draw up all the tidal stream atlas pages.
Psycho Warren said:
As long as you have a decent safety factor you should avoid running aground.
In my day we had to do it all from old fashioned paper tide tables and draw everything on the paper chart. Electronic charting software and tidal software was beginning to come of age but that was a back up and not to replace doing it "properly". The software was a very early version called "total tide" and to be fair to it, as long as you but decent data in it, the answers were correct.
Yup, me too.In my day we had to do it all from old fashioned paper tide tables and draw everything on the paper chart. Electronic charting software and tidal software was beginning to come of age but that was a back up and not to replace doing it "properly". The software was a very early version called "total tide" and to be fair to it, as long as you but decent data in it, the answers were correct.
I was taught to navigate at school in the '70s and did my RYA courses when GPS and chartplotters were still on the drawing board.
A chartplotter came with my boat but it's ancient and the last available update for it was 2006 and that means it's way too risky to even think about using it for navigation among the shifting sandbanks and swatchways where I sail.
Whenever I have to get serious with navigation I'll give one of the deck hippos a safety course to steer for 5 minutes and work out where I am and where I should be heading with a paper chart, tide tables and atlas.
Works for me.

Not 100% sure but think Savvy Navvy app may do stuff like that - i tried it for a small part of the free trial, but feel Navionics was a better bet for sailing. That said it has a lot more (paid for) features to aid navigation than Navionics, routing included wind directions which was a good idea.
Psycho Warren said:
L_G said:
Of course a better solution would be to take the reading from actual tide gauges, such as the one you mention, rather than using predictions but I'm still not convinced it is entirely a good idea.
As long as you have a decent safety factor you should avoid running aground. I am not surprised there is now "an app for that". lol
In my day we had to do it all from old fashioned paper tide tables and draw everything on the paper chart. Electronic charting software and tidal software was beginning to come of age but that was a back up and not to replace doing it "properly". The software was a very early version called "total tide" and to be fair to it, as long as you but decent data in it, the answers were correct.
I still remember the bane of having to draw up all the tidal stream atlas pages.
I suspect a similar situation could occur where the system thought there was a greater riser of tide than there really was and boat owners ended up aground because the chart software said there would be enough water.
That said, I know of someone who used the previous years tide tables by mistake when calculating when to arrive at a river with a shallow bar.
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