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Old 01-04-2015, 15:37   #1
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OpenCpn Tide time 1 hour out

I've been using OpenCPN for about 2 years and have found it invaluable as a backup to my on-board Raymarine C80.
Whilst I do ot rely upon OpenCPN tide times I have found that it seems to display an error of 1 hour. The RED line (indicating present time) is alway 1 hour behind the PC system time. Maybe I haven't set something up correctly, but I can't seem to fix it.
Any suggestions on a possible fix would be extremely welcome.

I've tried to attach a screenshot which shows the error as indicated by the blue line between system time and current tide height (Using Ubuntu 14.04 but was the same in 12.04).
Sadly the marina wifi is veryvery slow where I am. Takes minutes to download a page view!

Addendum
I should add that the tide height at the red line seems to be correct, it's just the time-scale along the bottom that seems to be out by 1 hour, example High tide now at Dover (1st april 2015) is 22:51, 6.1m from Dover marina handbook. Graph from Open CPN shows 21:47, 6.09m, I'm happy with 4 minutes and 0.01m but the hour is a concern!
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Old 01-04-2015, 16:01   #2
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Re: OpenCpn Tide time 1 hour out

Never looked at that..but have noticed that it does recognize daylight savings time....

Yet like you...often find it is an hour different in reality to the actual tide...need to revisit the error I perceive.
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Old 02-04-2015, 01:17   #3
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Re: OpenCpn Tide time 1 hour out

The times given are in local time.
Under the graph is written Z +01:00, wich means Zonetime 1 hour east of Greenwich or in this case UK summertime
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Old 02-04-2015, 05:02   #4
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Re: OpenCpn Tide time 1 hour out

Here is the results of the vector average of 9 years of data for Dover, England. The predictions are for the full program. The zone time is GMT.
As you can see, there seems to be a little problem!
2015/04/01 04:13 04.951 feet
2015/04/01 09:33 19.282
2015/04/01 16:33 04.886
2015/04/01 21:50 20.129

Best Regards.
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Old 02-04-2015, 12:38   #5
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Re: OpenCpn Tide time 1 hour out

Quote:
Originally Posted by rooiedirk View Post
The times given are in local time.
Under the graph is written Z +01:00, wich means Zonetime 1 hour east of Greenwich or in this case UK summertime
I agree, the times are "Local time" which is presently Z+1.
The red line on the graph is 1 hour different to the local PC time which is Z+1.

For completeness I also checked it last month which was not daylight saving and we were Z+0 (GMT). the red line on the graph was still 1 hour behind the local PC time and the timescale under the graph read Z + 00:00.

In both cases the actual tide height at the red line was correct, it's just the timescal underneath which is always 1 hour behind the PC local time. Confusing!
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Old 02-04-2015, 13:06   #6
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Re: OpenCpn Tide time 1 hour out

Quote:
Originally Posted by P_Dub View Post
Here is the results of the vector average of 9 years of data for Dover, England. The predictions are for the full program. The zone time is GMT.
As you can see, there seems to be a little problem!
2015/04/01 04:13 04.951 feet
2015/04/01 09:33 19.282
2015/04/01 16:33 04.886
2015/04/01 21:50 20.129

Best Regards.
I'm not sure what you're quoting. I've got to admit you've lost me a bit there.

I'm not concerned about a few minutes either way or even fractions of a meter difference, that occurs using different tidal calculations and the accuracy is never that precise anyway, due mainly to atmospheric pressure.
The only concern I have is that the timescale under the graph on OpenCPN appears to be 1 hour behind what it should be. In the example I showed it was supposedly accounting for daylight saving but give the impression that this was not applied. In fact it did apply it but the time in the graph was wrong by 1 hour.

It was still 1 hour different 1 month ago when we were not in daylight saving time.

That apart, OpenCPN is still a brilliant package.
For information, I arrived in Dover this evening and noticed that an "aircraft" symbol appeared on screen as an AIS target, Investigation showed it to be a "Search and Rescue" aircraft which was in fact a helicopter. This did not show as a marker on my Raymarine plotter (which receives the same AIS info). I didn't realise they used AIS, This is brilliant, because, when in need, you can advise them what bearing and distance they are from you (assuming your electronics is still operational).
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Old 02-04-2015, 18:24   #7
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Re: OpenCpn Tide time 1 hour out

In the Harmonic file try to find the following:-

# British Data, TZ+0.0
# !longitude: 1.3181
# !latitude: 51.1165
Dover, England - READ flaterco.com/pol.html
0:00 :Europe/London
3.7564 meters


and enter the following line:-
# British Data, TZ+0.0
in the same place that I did put it
This would most likely be the cause of it.




If it does not work, then replace the line by this:-


# DOVER, ENGLAND 51d07.0'N 1d19.1'E
# METRES
# ENGLAND DATA, TZ+0.0
# (ANALYSIS 2009-2010 Chart Datum)
# !units: metres
# !longitude: 01.3183
# !latitude: 51.1167
DOVER, England
-00:00 :Europe/London
3.7643 metres
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Old 04-04-2015, 04:28   #8
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Re: OpenCpn Tide time 1 hour out

Quote:
Originally Posted by P_Dub View Post
In the Harmonic file try to find the following:-

# British Data, TZ+0.0
# !longitude: 1.3181
# !latitude: 51.1165
Dover, England - READ flaterco.com/pol.html
0:00 :Europe/London
3.7564 meters


and enter the following line:-
# British Data, TZ+0.0
in the same place that I did put it
This would most likely be the cause of it.




If it does not work, then replace the line by this:-


# DOVER, ENGLAND 51d07.0'N 1d19.1'E
# METRES
# ENGLAND DATA, TZ+0.0
# (ANALYSIS 2009-2010 Chart Datum)
# !units: metres
# !longitude: 01.3183
# !latitude: 51.1167
DOVER, England
-00:00 :Europe/London
3.7643 metres
Hi, Many thanks.
I tried both solutions but it made no difference.
After some further investigation I found that this wasn't just related to the UK.

I also tried (for the 1st time) loading and running OpenCPN in "WINDOWS"
I've not used Windows for ages and I needed to put the system clock back an hour.
I downloaded OpenCPN (4.0 - same as in LINUX)
All seemed OK there with the times being displayed correctly!!!

I then re-booted in LINUX (UBUNTU 14.04) and the 1 Hour error was back.
I even made sure this time that I used the same HARMONIC.IDX as windows was using "(Program Files (x86)/OpenCPN/tcdata/HARMONIC.IDX)"
It would appear then that this may not be an OpenCPN issue but an issue with the way that UBUNTU or LINUX deals with daylight saving times.

Trouble is - I just hate "Windows" these days.
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Old 04-04-2015, 09:35   #9
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Re: OpenCpn Tide time 1 hour out

silentwings39

I have no problem with my *buntu boxes

To make sure your Linux box is set to a correct time run
Quote:
$sudo dpkg-reconfigure tzdata
and enter the correct info.
I get this return from the command
Quote:
Current default time zone: 'Europe/Copenhagen'
Local time is now: Sat Apr 4 17:23:36 CEST 2015.
Universal Time is now: Sat Apr 4 15:23:36 UTC 2015.
At least, after this we will know your Linux settings.

Thomas
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Old 04-04-2015, 10:47   #10
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Re: OpenCpn Tide time 1 hour out

Hi Thomas/Cagney.

Tried that too now.... Still no better. The red line is still shown as 1 hour behind local time

the time settings appeared OK, I didn't have to change any and the result is:-
Current default time zone: 'Europe/London'
Local time is now: Sat Apr 4 17:41:04 BST 2015.
Universal Time is now: Sat Apr 4 16:41:04 UTC 2015.

I don't understand why the red line in the tide graph is different in Ubuntu from windows!
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Old 18-04-2016, 11:35   #11
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Re: OpenCpn Tide time 1 hour out

Quote:
Originally Posted by silentwings39 View Post
I've been using OpenCPN for about 2 years and have found it invaluable as a backup to my on-board Raymarine C80.
Whilst I do ot rely upon OpenCPN tide times I have found that it seems to display an error of 1 hour. The RED line (indicating present time) is alway 1 hour behind the PC system time. Maybe I haven't set something up correctly, but I can't seem to fix it.
Any suggestions on a possible fix would be extremely welcome.

I've tried to attach a screenshot which shows the error as indicated by the blue line between system time and current tide height (Using Ubuntu 14.04 but was the same in 12.04).
Sadly the marina wifi is veryvery slow where I am. Takes minutes to download a page view!

Addendum
I should add that the tide height at the red line seems to be correct, it's just the time-scale along the bottom that seems to be out by 1 hour, example High tide now at Dover (1st april 2015) is 22:51, 6.1m from Dover marina handbook. Graph from Open CPN shows 21:47, 6.09m, I'm happy with 4 minutes and 0.01m but the hour is a concern!
After several years without using the Tide calculator of OpenCPN I returned to it today. It is curious that 2 years ago it was ok but now the same error that you indicate appears on OpenCPN v4.2.0.

Any news about this bug since your last post?

Best regards

Joo Blasques

Lisbon, Portugal
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Old 20-04-2016, 15:50   #12
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Re: OpenCpn Tide time 1 hour out

The same problem here with Windows OpenCPN 4.2 and 4.2.1. OTCurrent and Tide-Finder are affected by these calculations.

Please can this be looked at quickly.

Mike
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Old 20-04-2016, 23:19   #13
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Re: OpenCpn Tide time 1 hour out

I think the problem may lie with how wxWidgets 3.0.2 handles daylight saving time (dst) (Windows only?).

Tested this by changing my pc date to 01 March 2016 and the problem disappeared. I have now reset the pc to today's date and utc without dst correction and again the predictions have the correct time. This will be my workaround at the moment.

(Working on the ncdf plugin recently I encountered a time anomaly when doing date/time calculations which involved daylight saving time)

Mike
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Old 21-04-2016, 15:17   #14
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Re: OpenCpn Tide time 1 hour out

Hi all

Yes I think there is a bug in wxWidgets 3x
It occurs only when meridian is UTC (London for example ) and time is DST.
In this case, there is no difference between UTC and Local time. In others terms, now() is equal to now().ToGmt() whereas there should be one hour offset.
(I had to fix a similar problem in grib_pi )
What worry me is the error I see under windows is the contrary the one you
see under Linux...
Nevertheless, the fix is easy and work fine at least under Windows (see second screen shot
Jean Pierre
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Old 21-04-2016, 15:41   #15
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Re: OpenCpn Tide time 1 hour out

There is no bug, the problem lies into the data itself, which were set up for the time of France ( GMT +1 as standard time and GMT +2 as summer time ).
I have redone everything and it works correctly. Someone must have done it to be used on the France time. Many stations were fairly incorrect in the predictions, due to incorrect processing. Unfortunately, I can not at the moment able to send you the file, being in the process of building my new computer with Windows 10 pro and not having time to do so.
Best regards to you.
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