Next Tide Event Time

[SerialHobbyist]

I'm not quite sure how to explain this...


The "Next tide event" column in route properties is calculating incorrectly for me.


I have "Time shown as" set to "Local @ PC". The next tide event column is, however, showing the next tide event AFTER local time + 7 hours. It appears to be treating UTC as local time, since I am UTC-7.


Does that make sense?

[bdbcat]

Serial...

What is your location/tide station?

Dave

[bdbcat]

Serial...

More info needed. Screenshots, route info, etc....

Thanks
Dave

[SerialHobbyist]

http://floogle.net/Screenshot2018-07-29.png

This shows the next tide event should be the low tide @ 11:40, however the route properties is showing the next event as the high tide @ 19:24.


Additionally, I modified the code to subtract a magic number of 7 hours (I'm at UTC-7) and it then displays the correct tide event info.

[bdbcat]

Serial...

This is indeed a bug. The logic to calculate the next BigEvent at a tide station is flawed, becoming offset by the local time zone.

Will be fixed in the next release.

Thanks for the catch
Dave

[SerialHobbyist]

I really wanted to submit a fix for it, but I'm not familiar enough with the code yet and I'm not sure how best to get the user's timezone. I think the value tz passed into RouteProp::MakeTideInfo with a value of 1 is specifying it should be in "pc local" time, right?

[bdbcat]

Serial....

Close. This issue was that GetNextBigEvent() should be called with local time, not UTC.

Try this code, which is the commit I will push when I get back to master branch again.

wxString RouteProp::MakeTideInfo( int jx, time_t tm, int tz_selection, long LMT_Offset )
{
    int ev = 0;
    wxString tide_form;
    
    // tm comes in as UTC...
    // convert to local time for GetNextBigEvent
    wxDateTime now = wxDateTime::Now();
    wxDateTime nowutc = wxDateTime::Now().MakeUTC();
    time_t t_off = now.GetTicks() - nowutc.GetTicks();
    
    wxDateTime dtmu;
    dtmu.Set( tm + t_off );

    time_t dtmtt = dtmu.GetTicks();
    
    if( gpIDX ) {
        ev = ptcmgr->GetNextBigEvent( &dtmtt,
                ptcmgr->GetStationIDXbyName( wxString( gpIDX->IDX_station_name, wxConvUTF8 ),
                        gpIDX->IDX_lat, gpIDX->IDX_lon ) );
    } else
        ev = ptcmgr->GetNextBigEvent( &dtmtt, jx );

    //convert event time back to UTC
    wxDateTime dtm;
    dtm.Set( dtmtt ).MakeUTC(); 
    
    if( ev == 1 ) tide_form.Printf( _T("LW: ") );
    if( ev == 2 ) tide_form.Printf( _T("HW: ") );
    
    tide_form.Append( ts2s( dtm, tz_selection, LMT_Offset, DISPLAY_FORMAT ) );
    if( !gpIDX ) {
        wxString locn( ptcmgr->GetIDX_entry( jx )->IDX_station_name, wxConvUTF8 );
        tide_form.Append( _T(" @~~") );
        tide_form.Append( locn );
    }
    return ( tide_form );
}

Dave

[SerialHobbyist]

Makes sense.


But, am I overcomplicating things, or doesn't it need to take into account whether the user has selected "UTC", "local @ PC", or "LMT"?


I guess I was assuming that it originally worked correctly for UTC.

[bdbcat]

Serial...

The user tz selection is only about what is displayed, and is handled by
ts2s() parameters..

But try it out, and let me know how it works in the various options.
This TZ stuff always leaves me head-scratching......

Dave

[SerialHobbyist]

I quickly tested your code change and it fixed my UTC-7 problem, and using the UTC setting also seems to work correctly with it.


I don't understand the use-case for LMT, so I didn't test it.

[skipperearly]

I often wondered what to expect in the route manager in the "next tide event" column. Is there any specific setting to be made to get these values calculated/shown.
Have also tried with the otcurrent_pi

In the manual I didnt find anything related.

Was looking for some recalculate or update option to plan a route with route manager and then finally activate it and get it updated on the way.

To show tidal information in the route plan would be really great.

[bdbcat]

Skipper...

If you do two things, the column is populated.

1. Before opening route manager, open the graphic for a specific tide station. This will be the location for which "next tide event" is calculated.

2. Open the route manager. Fill in a value for "departure time", and hit return.

The next event column will then be populated.

Dave

[SerialHobbyist]

Also, if you set the waypoint name in a special way, you can "tie" the waypoint to a specific tide station.


To do so, open the waypoint properties and change the name of the waypoint to include the special characters "@~~" immediately followed by the tide station name (or at least a unique beginning to the tide station name -- it will match the first tide station that begins with those characters). e.g. "001 @~~Port Townsend (Point Hudson), Washington" You still need to set a "Departure time" before the column will be populated.



Unfortunately, this does not work for current stations, which would be much more useful for me. I sail in the San Juan and Gulf Islands of the Pacific Northwest and it's an unusual day that the currents would not be an issue.


I'm currently testing a patch that does show the current data. However this method of modifying the waypoint name seems a bit of a hack -- I'd rather it was a more obvious and usable feature.


Chas

[skipperearly]

@SerialHobbyist thanks for this info - great feature and it works!
Got a bit confused with the date and time format and assume it works only with UTC flawlessly.
Only snag when printing the route the tide event column cannot be selected to get printed - and starting date/time doesn't get remembered.

[SerialHobbyist]

Yes, trying to use local PC time currently has a bug -- which started this thread.


I'm seeing the Departure Time randomly disappearing and I'm looking for what might cause it. It's really "bugging" me...


Chas