Reply
 
Thread Tools Display Modes
 
Old 03-23-2015, 04:14 PM   #1
Guru
 
JDCAVE's Avatar
 
City: Lions Bay, BC
Country: Canada
Vessel Name: Phoenix Hunter
Vessel Model: Kadey Krogen 42 (1985)
Join Date: Apr 2011
Posts: 1,602
Tidal analysis using spreadsheets

Have any of the physicists on the forum taken the time to develop a tidal algorithm using information from reference and secondary ports?

This is what I am asking about:

"R. de Levie, Tidal analysis on a spreadsheet, Am. J. Phys. 72 (2004) 644-651.

Abstract available here:
Tidal analysis on a spreadsheet - ResearchGate




Jim
Sent from my iPad using Trawler Forum
__________________
Advertisement

JDCAVE is offline   Reply With Quote
Old 03-23-2015, 04:55 PM   #2
Guru
 
JDCAVE's Avatar
 
City: Lions Bay, BC
Country: Canada
Vessel Name: Phoenix Hunter
Vessel Model: Kadey Krogen 42 (1985)
Join Date: Apr 2011
Posts: 1,602
Ok. I found this calculator and verified the trend and it seems to make some sense.
http://www.linz.govt.nz/system/files...d=1&download=1
Still pretty cludgey. Looking for something more elegant.


Jim
Sent from my iPad using Trawler Forum
__________________

JDCAVE is offline   Reply With Quote
Old 03-23-2015, 05:01 PM   #3
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,720
That's a lot of work. lol Have you looked at WXTide 32? It's free and it also does currents. OpenCpn has good (free) tide and current information. We usually compare the 2, see what is actually happening and judge from there.

WXTide32 - Tides and Currents for Win9x/NT
Larry M is online now   Reply With Quote
Old 03-23-2015, 07:55 PM   #4
Guru
 
JDCAVE's Avatar
 
City: Lions Bay, BC
Country: Canada
Vessel Name: Phoenix Hunter
Vessel Model: Kadey Krogen 42 (1985)
Join Date: Apr 2011
Posts: 1,602
I've got AyeTides on the iPad and another program embedded in the Coastal Explorer. It's just the modeller in me that wants to explore my own models. I've since found the above "NZ" site that gets me close but I want more functionality and to make it more user friendly.

The physicist I used to work with did some pretty whizzy modelling of time series data including river heights, tidal cycles and fish flux dynamics, using "Fast Fourier Transforms". But that's a bit beyond a spread sheet tool.


Jim
Sent from my iPad using Trawler Forum
JDCAVE is offline   Reply With Quote
Old 03-23-2015, 08:08 PM   #5
GFC
Guru
 
GFC's Avatar
 
City: Tri Cities, WA
Country: USA
Vessel Name: Beachcomber
Vessel Model: Sea Ray 550 Sedan Bridge
Join Date: Nov 2012
Posts: 2,684
Dang, I read that first sentence on the first link and realized it's way beyond my simple minded little brain.

I'll stick with the tide tables or what I have on my phone.
__________________
Mike and Tina
Beachcomber 1995 Sea Ray 550 Sedan Bridge
GFC is offline   Reply With Quote
Old 03-23-2015, 09:33 PM   #6
Guru
 
JDCAVE's Avatar
 
City: Lions Bay, BC
Country: Canada
Vessel Name: Phoenix Hunter
Vessel Model: Kadey Krogen 42 (1985)
Join Date: Apr 2011
Posts: 1,602
It's beyond my simple pea brain too. However, I managed to get the calculator working fine, but it's "brute strength" and isn't smart. I'd like it to react and update with changing inflection points (High low tides) and changing times. I'm surprised there aren't spread sheet templates on the internet for these calculations.


Jim
Sent from my iPad using Trawler Forum
JDCAVE is offline   Reply With Quote
Old 03-23-2015, 09:36 PM   #7
Guru
 
JDCAVE's Avatar
 
City: Lions Bay, BC
Country: Canada
Vessel Name: Phoenix Hunter
Vessel Model: Kadey Krogen 42 (1985)
Join Date: Apr 2011
Posts: 1,602
Forgot the graph...
Click image for larger version

Name:	ImageUploadedByTrawler Forum1427160963.483908.jpg
Views:	70
Size:	76.7 KB
ID:	38480


Jim
Sent from my iPad using Trawler Forum
JDCAVE is offline   Reply With Quote
Old 03-23-2015, 09:47 PM   #8
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
What's the point?
Capt.Bill11 is offline   Reply With Quote
Old 03-23-2015, 10:02 PM   #9
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Quote:
Originally Posted by Capt.Bill11 View Post
What's the point?
Good question. Aside from the desire to do something oneself just for the challenge, it seems a lot of work just to get to the same place I can get to on my iPad with a couple of screen taps and then slide the timeline to see what the tide will be at any point during the 24 hour period.
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	51
Size:	114.9 KB
ID:	38481  
Marin is offline   Reply With Quote
Old 03-24-2015, 05:37 PM   #10
Guru
 
JDCAVE's Avatar
 
City: Lions Bay, BC
Country: Canada
Vessel Name: Phoenix Hunter
Vessel Model: Kadey Krogen 42 (1985)
Join Date: Apr 2011
Posts: 1,602
Quote:
Originally Posted by Capt.Bill11 View Post
What's the point?
Quote:
Originally Posted by Marin View Post
Good question. Aside from the desire to do something oneself just for the challenge, it seems a lot of work just to get to the same place I can get to on my iPad with a couple of screen taps and then slide the timeline to see what the tide will be at any point during the 24 hour period.
Because I wanted to. I felt the learning experience was worth it. Sure, I have 3rd party software as well, but I wanted a tool to explore the CHS Canadian Tide and Current Tables in more detail and I was unable to find a spreadsheet template for this purpose on the internet. Also, I have a sense that the 3rd party software may use Alaskan tidal stations for reference to predict Central Area Tides and Currents, rather than the CHS reference stations.

I now have a working model that is robust to changes in inputs. No, I didn't use anything fancy such as rigorous time series analysis. Such an analysis is only useful with large historical time series (50-100 years of tidal records). So I developed a simple model for a single day, using the daily tide tables published by CHS.

The model:
h = h1 + (h2 - h1)[(cosA + 1)/2],
where A = π([(t - t1)/(t2 - t1)] + 1) radians
(Australian Hydrographic Service).
h1 = height from tide table at time t1
h2 = height from tide table at time t2
h...hn = incremental height at time t....tn (to be calculated between h1 and h2)

The model can also be used for currents by substituting tidal height with current in knots (+/-). The prediction model for currents shows some bias in estimates of “time of slack water”, with deviation of +/- 2-15 minutes, with increasing bias with increased time interval between peak current. This is probably due to the model’s inability to capture the correct asymmetry inherent in CHS predictions. The prediction model for tidal height appears to be reasonable for most purposes.

Jim
JDCAVE is offline   Reply With Quote
Old 03-24-2015, 07:00 PM   #11
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,856
In many places the tidal predictions based on astronomy are sufficiently altered by environmental conditions ....fiddling too much with predictions might be a nice hobby...but useless for navigational purposes.

The predictions will give a ballpark and that's as good as it will get.

Some places with large tides and currents may be a better area for tweaking.
psneeld is offline   Reply With Quote
Old 03-24-2015, 08:04 PM   #12
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,720
Quote:
Originally Posted by Larry M View Post
...We usually compare the 2, see what is actually happening and judge from there....
Quote:
Originally Posted by psneeld View Post
...The predictions will give a ballpark and that's as good as it will get.

Some places with large tides and currents may be a better area for tweaking.
__________________

Larry M is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 10:26 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012