Tidal data and course to steer

[MFox]

Is it possible to input UK and Europe tidal data into OpenCPN and if so where can I find that data and can OpenCPN calculate Course to Steer?
Thank you

[CarCode]

Look for HARMONIC file V9, V10 or from merak56 to have tidal data for european waters also. OpenCPN always shows you the course to steer, simple look in the user manual to know how.

[SamH]

Originally Posted by MFox

Is it possible to input UK and Europe tidal data into OpenCPN and if so where can I find that data and can OpenCPN calculate Course to Steer?
Thank you

You can find HARMONICS V10 here:
Martine, Pierre et leur voilier Logos

OpenCPN manual here:
https://opencpn.org/wiki/dokuwiki/do...s_and_currents

(The manual is almost up to date, but the buttons to display tide and stations is now under the menu available from the lower right corner)

[muttnik]

Originally Posted by CarCode

OpenCPN always shows you the course to steer, simple look in the user manual to know how.

Apologies in advance if the answer is "yes" but are you sure you understand what the OP means by "Course to Steer" in this context?

I'm definitely out of date with OCPN but I can't seem to find any mention of it in the manual

[CarCode]

Originally Posted by muttnik

Apologies in advance if the answer is "yes" but are you sure you understand what the OP means by "Course to Steer" in this context?

I'm definitely out of date with OCPN but I can't seem to find any mention of it in the manual

If you have no destination you will also have no course to steer. So where to go and where to steer? To understand how a navigation software works it is almost a good idea to study the manual.

[muttnik]

Originally Posted by CarCode

If you have no destination you will also have no course to steer. So where to go and where to steer? To understand how a navigation software works it is almost a good idea to study the manual.

I believe you are interpreting "course to steer" in a colloquial sense whereas the OP intended it in the navigational sense, i.e.:
Sailtrain: Navigation and Chartwork,

Some navigational software will work this out for you (although I've no experience with any that does) but I don't believe OCPN does...I could be wrong and happy to be corrected but I haven't found anything about it in the manual.

[CarCode]

Originally Posted by muttnik

I believe you are interpreting "course to steer" in a colloquial sense whereas the OP intended it in the navigational sense, i.e.:
Sailtrain: Navigation and Chartwork,

Some navigational software will work this out for you (although I've no experience with any that does) but I don't believe OCPN does...I could be wrong and happy to be corrected but I haven't found anything about it in the manual.

I know British people are something different than others. But sailing without knowing where to go is new for me. I have always a destination and sailing to this destination OpenCPN shows me the course to steer.

[muttnik]

Originally Posted by CarCode

I know British people are something different than others. But sailing without knowing where to go is new for me. I have always a destination and sailing to this destination OpenCPN shows me the course to steer.

Maybe it's because the tides are much stronger here than in Greece :-)

If I want to sail somewhere which is on a bearing of X degrees true from where I am, in a tidal area, leaving aside weather routing or leeway, if I just correct for variation and deviation then dial the resulting magnetic course into the autopilot I likely *won't* end up at my desired destination. Why? Because while I maintained a constant course through the water, the water itself was moving relative to the ground because of tidal currents. So "Course To Steer" (which is a particular phrase used for this calculation) needs to be corrected for the effects of tide. This becomes more involved the longer the leg you are calculating for because tides change not only with time but also location: In the classic example your average Brit will use for CTS calculations, ie crossing the channel / la manche, the tide runs harder in different parts of the channel so hourly tidal estimates need to be based not only on a time but an estimated location.

A lot of people would be more than happy to have the hard work taken out of that calculation. My chart plotter can't do it. Some higher end software claims to be able to and we've had discussions about that before. e.g:

https://www.cruisersforum.com/forums...re-233035.html

To summarise: I believe the question the OP was asking was "Can OCPN calculate the course to steer from A to B taking into consideration tidal effects between A and B". From looking at the manual I don't believe OCPN can but I'm happy to be corrected.

[dannc]

Originally Posted by muttnik

...

To summarise: I believe the question the OP was asking was "Can OCPN calculate the course to steer from A to B taking into consideration tidal effects between A and B". From looking at the manual I don't believe OCPN can but I'm happy to be corrected.

Yes, that was my understanding of the question and I would like to know if OCPN can do the calculations. I will be most impressed if it can.

Later,
Dan

[CarCode]

Originally Posted by muttnik

Maybe it's because the tides are much stronger here than in Greece :-)

So I wish you happy sailing and please stop your postings now...

[Hakan]

To summarize: I believe the question the OP was asking was "Can OCPN calculate the course to steer from A to B taking into consideration tidal effects between A and B". From looking at the manual I don't believe OCPN can but I'm happy to be corrected.

If you "draw a line from A to B": In practical is that what you do when you ask an Auto Pilot to navigate to a certain point. The initial course line could then be e.g. 200°. If you have a leeway by the current you'll be off the line after a while. OCPN is calculating the XTR that is the error the AP have to adjust to keep the COG pointing to B (or back to the line). After a while will the heading be e.g. 190° to have the COG pointing to 200°. That combined result is a "course to steer" 190° to maintain a bearing of 200°. OCPN is calculating the error and the AP is translating that to a heading.

[muttnik]

Originally Posted by Hakan

OCPN is calculating the error and the AP is translating that to a heading.

Bad example on my part: I should have talked about handing the CTS to the helmsperson rather than the autopilot. I pretty much exclusively use the autopilot to steer a fixed heading (and that's what I meant). I see my example created confusion because many people don't use an autopilot like that but instead put a GPS waypoint into the autopilot and say "go to waypoint", which I believe is what you're talking about here.

The discussion has been had several times before on cruisersforum (including a link I posted above) but going to a GPS waypoint rather than steering a fixed heading is inefficient when crossing a significant, changing tidal stream because whilst the autopilot keeps your course over ground constant, you end up travelling further through the water.

[dannc]

Originally Posted by muttnik

Bad example on my part: ...

I think you example is perfectly fine. People just don't seem to understand what you are asking.

Later,
Dan

[CarCode]

What about to take some lessons at a sailing school for you guys when you are new to sailing? I guess you will have sailing schools in your country. I'm not a teacher and a forum is also a bad place for teaching. So it will be better to get some lessons before going sailing. I'm sailing since more than 60 years now (about 40 years in the Mediterranian and 20 years in the North Sea) and can only shake my head when reading this thread. And if you want to have digitized sailing you need a boat with the suitable sensors, only a GPS is not suffizient.

[Dsanduril]

"Course to steer" is a pretty well defined navigational term and the point is being missed (by some). The point of CTS is to have XTE=0 at the end of your passage while steering a constant heading throughout the passage.

The AP XTE examples presented react in real-time to current XTE, with CTS you don't care about XTE now, you only care about XTE (as long as you don't pass over land or something like that) at the end of the passage. It takes planning for tidal currents, ocean currents, and leeway and so is only a guess (an educated one if you do it right).

Not using CTS, and using instantaneous XTE to keep correcting, with tide pushing one direction you may end up having to head up to the point of beating (probably against a contrary current), whereas if you had started out headed up a little bit because you planned for the tide you may be able to make your destination without having to tack. The distance sailed difference in most cases is relatively small, but the total time, especially if you end up beating at the end of the passage instead of close reaching from the start, can be significant.

I have not used it for this, but my recollection is that the weather routing plugin for OpenCPN can take into account currents, but I don't know if it can do so without a weather file (and polars) loaded at the same time.