Predictions do not match numbers on tidesandcurrents.noaa.gov

[akrenner]

The Bug

Predictions from tide_slack_data do not match figures on the official noaa.gov site. While figures for provided bandywine datasets still match fairly closely (10 to 30 min discrepancy), for 2024 there are wide discrepancies:

tide_slack_data(data.frame (Station=tide_stations("Brandy")
                            , DateTime=as.POSIXct(c ("2024-05-07 03:00",
                                                     "2024-05-07 09:00",
                                                     "2024-05-07 15:00",
                                                     "2024-05-07 21:00"),
                                                     tz="GMT")))
# 2024-05-05 03:15:33           0.303 low      
# 2024-05-05 09:15:33           1.35  high  
# 2024-05-05 15:15:33           0.377 low      
# 2024-05-05 21:15:33           1.29  high   

Whereas from NOAA:

00:26 1.87 m H

06:47 -0.17 m L

12:54 1.57 m H

18:48 -0.14 m L

Also note that the 2024 results from tide_slack_data are all the 15:33 min away from the provided times. This also holds true for other 2024 or 2025 times, but not for 2023-05-05.

[joethorley]

Thanks @akrenner

I'll try and tackle next week.

[akrenner]

Thank you so kindly! Martin

…

On Tue, May 7, 2024 at 2:36 PM Joe Thorley ***@***.***> wrote: Thanks @akrenner <https://github.com/akrenner> I'll try and tackle next week. — Reply to this email directly, view it on GitHub <https://github.com/poissonconsulting/rtide/issues/26#issuecomment-2099424991>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/APZWLP5OEVCJE6DOCDXEUITZBFJP3AVCNFSM6AAAAABHKSXFBSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAOJZGQZDIOJZGE> . You are receiving this because you were mentioned.Message ID: ***@***.***>

-- Martin Renner CSS, Inc. under contract to NOAA Kasitsna Bay Lab Marine Spatial Ecology Division National Centers for Coastal Ocean Science 95 Sterling Highway, Suite 2, Homer AK 99603 phone: 323 372-1870

[akrenner]

I revisited this issue recently, now using rtide v 0.0.11. For the same example as above, I now get different values, but they still appear to be wrong. Previously, all SlackDateTimes were 15 min past provided times, now they are all 44 min, 27 seconds later. That can't be and indeed does not match predictions from the NOAA site. My suggestions: pull data from the NOAA site directly, until the underlying issue here can be fixed (I can provide some code to do that, if that's of interest).

[joethorley]

@akrenner - I've had to step back from maintenance due to time constraints. I'm not sure about @millerlp availability?