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  1. #1
    Join Date
    Nov 2002
    Location
    West Mersea
    Posts
    6,345

    Default SW Sunk swatchway

    Ian and Sarah crossed the SW Sunk swatchway yesterday at low water springs. They took great care to time, record and hold exactly to the recommended track using the three waypoints.

    Worse depths at chart datum had at least 3m in the swatch towards the east. The east side is, of course, the shallow side. Possibly the swatch has shallowed slightly but it is still very feasible. The depths recorded were:

    Depths taken
    Western side waypoint: 8.3m
    Midway Between the Western side and central point: 5m
    Central point waypoint: 5m
    Between the central point and the Eastern side: the shallowest was 3.8m
    Eastern side waypoint: 4.5m

    Margate predicted tidal height at the time was 0.74m, and based on PLA actual data 0.4m. Margate is within an inch or so of the SW Sunk swatch so can be used as a quick point of reference e.g. 3.4m worst.

    It may be the swatch has migrated a little - it has in previous years - but I would suggest the waypoints should continue to be used. As soon as I can get launched (and I'm ready) I shall do a comprehensive survey.

    Thanks to Ian and Sarah for their work.
    www.crossingthethamesestuary.com

  2. #2
    Join Date
    May 2012
    Location
    Summer Walton, Winter Iberia
    Posts
    9,305

    Thumbs up Re: SW Sunk swatchway

    Quote Originally Posted by tillergirl View Post
    Ian and Sarah crossed the SW Sunk swatchway yesterday at low water springs. They took great care to time, record and hold exactly to the recommended track using the three waypoints.

    Worse depths at chart datum had at least 3m in the swatch towards the east. The east side is, of course, the shallow side. Possibly the swatch has shallowed slightly but it is still very feasible. The depths recorded were:

    Depths taken
    Western side waypoint: 8.3m
    Midway Between the Western side and central point: 5m
    Central point waypoint: 5m
    Between the central point and the Eastern side: the shallowest was 3.8m
    Eastern side waypoint: 4.5m

    Margate predicted tidal height at the time was 0.74m, and based on PLA actual data 0.4m. Margate is within an inch or so of the SW Sunk swatch so can be used as a quick point of reference e.g. 3.4m worst.

    It may be the swatch has migrated a little - it has in previous years - but I would suggest the waypoints should continue to be used. As soon as I can get launched (and I'm ready) I shall do a comprehensive survey.

    Thanks to Ian and Sarah for their work.
    Great work✔️

    To make it easier to visualise, are they going to produce an unofficial diagram of their findings, with the usual disclaimer that the diagram is not for navigation and only used at a skippers discretion❓

    Although others may carry out a similar exercise, once I am back in the water, I will do the same thing, at the entrance to The Walton Backwaters, around Stone Point.

    After all you cannot have too much information.
    🏴󠁧󠁢󠁥󠁮󠁧󠁿Neither a Remainer or a Leaver be. Hoping for the best but planning for the worst✔️

  3. #3
    Join Date
    Nov 2002
    Location
    West Mersea
    Posts
    6,345

    Default Re: SW Sunk swatchway

    http://www.crossingthethamesestuary.com/page29.html - Third chart down. That is the 2016 chartlet which has endured accurately and Ian and Sarah's data, whilst not to exacting to CD standards, shows that it is still very feasible. When I have redone the survey it will be properly reduced to chart datum for this year. Unfortunately I am held in the queue for launching hence the delay.
    www.crossingthethamesestuary.com

  4. #4
    Join Date
    Jun 2001
    Location
    UK East Coast
    Posts
    1,767

    Default Re: SW Sunk swatchway

    Quote Originally Posted by tillergirl View Post
    http://www.crossingthethamesestuary.com/page29.html - Third chart down. That is the 2016 chartlet which has endured accurately and Ian and Sarah's data, whilst not to exacting to CD standards, shows that it is still very feasible. When I have redone the survey it will be properly reduced to chart datum for this year. Unfortunately I am held in the queue for launching hence the delay.
    How easy would it be to bring your kit to my boat and plug into my depth transducer? I could then take you out for a day of surveying. Am already in the water on the Crouch.

    www.solocoastalsailing.co.uk

  5. #5
    Join Date
    Nov 2002
    Location
    West Mersea
    Posts
    6,345

    Default Re: SW Sunk swatchway

    Very easy... providing there is one stream of NMEA with a contemporaneous stream of lat/long, time and depth. Several lat/long strings can suffice - GLL, GGA, RWC strings and a few others will give timed lat/long and DBT or DPT. I need a RS232 output: that will feed my laptop and hoover up the data. A plotter that displays track is important to ensure sufficient coverage i.e. seeing where she has been to see comprehensiveness but my laptop will do that. Some power for the laptop would be useful but hopefully not essential.

    Other preferences

    A tolerance of boredom ( 3 hours of trundling back and forth over the swatch)
    Timing to low water springs in the morning (Is it me or is LW am springs later than it used to be - suppose that's global warming) - May 5, 6 or 7 next.
    Preferably less than 10 kts of wind (please, please no Easterly winds - don't expect to get a run back home; the wind will change the moment the Cruising Chute is hoisted - the point about the East wind is a swell can cause rolling which can raise the issue of accuracy )
    A notebook and pen or pencil - ah that may be difficult for many - to note things like 'it's rolling in that section', 'It's windy now')
    VHF to listen in the PLA tide heights.
    Barometer

    Giving that there have been 500 views on this thread I am hoping I can persuade the yard to fit me in - I know, I know. There weren't 500 requests to get a survey but what little understand I have of social media I can exaggerate that this is a national issue Also if still in the car park by 1st May, I shall be hauled up before the Committee for having a boat (or two) in the car park in breach of the Club Rules!!!! Fingers crossed but it is an idea Plum.

    Some of that in humour

    Oh, one other thing, what draught?
    www.crossingthethamesestuary.com

  6. #6
    Join Date
    Aug 2010
    Location
    Essex / sail out of Bradwell
    Posts
    550

    Default Re: SW Sunk swatchway

    Quote Originally Posted by nortada View Post
    Great work✔️

    To make it easier to visualise, are they going to produce an unofficial diagram of their findings, with the usual disclaimer that the diagram is not for navigation and only used at a skippers discretion❓

    Although others may carry out a similar exercise, once I am back in the water, I will do the same thing, at the entrance to The Walton Backwaters, around Stone Point.

    After all you cannot have too much information.
    Hi Nortada,

    We hope you are good.
    If you use Roger's chart it will serve you well.

    We are heading in your direction again for the may bank holiday.... how is Stone point? Are we ok to use the 2018 chartlet still?

    Ian and Sarah
    French Connection
    Yacht: French Connection / Jeanneau 37

  7. #7
    Join Date
    Feb 2007
    Location
    Essex
    Posts
    22,063

    Default Re: SW Sunk swatchway

    I look forward to the answer, but Stone Point doesn't seem to have changed much in the last couple of years so should be easy enough.
    Far away is near at hand in images of elsewhere

  8. #8
    Join Date
    Jun 2001
    Location
    UK East Coast
    Posts
    1,767

    Default Re: SW Sunk swatchway

    Quote Originally Posted by tillergirl View Post
    Very easy... providing there is one stream of NMEA with a contemporaneous stream of lat/long, time and depth. Several lat/long strings can suffice - GLL, GGA, RWC strings and a few others will give timed lat/long and DBT or DPT. I need a RS232 output: that will feed my laptop and hoover up the data. A plotter that displays track is important to ensure sufficient coverage i.e. seeing where she has been to see comprehensiveness but my laptop will do that. Some power for the laptop would be useful but hopefully not essential.

    Other preferences

    A tolerance of boredom ( 3 hours of trundling back and forth over the swatch)
    Timing to low water springs in the morning (Is it me or is LW am springs later than it used to be - suppose that's global warming) - May 5, 6 or 7 next.
    Preferably less than 10 kts of wind (please, please no Easterly winds - don't expect to get a run back home; the wind will change the moment the Cruising Chute is hoisted - the point about the East wind is a swell can cause rolling which can raise the issue of accuracy )
    A notebook and pen or pencil - ah that may be difficult for many - to note things like 'it's rolling in that section', 'It's windy now')
    VHF to listen in the PLA tide heights.
    Barometer

    Giving that there have been 500 views on this thread I am hoping I can persuade the yard to fit me in - I know, I know. There weren't 500 requests to get a survey but what little understand I have of social media I can exaggerate that this is a national issue Also if still in the car park by 1st May, I shall be hauled up before the Committee for having a boat (or two) in the car park in breach of the Club Rules!!!! Fingers crossed but it is an idea Plum.

    Some of that in humour

    Oh, one other thing, what draught?
    I can't help with the nmea/rs232 data but i can provide a bit of good humour and a ride out from Bridgemarsh Marina on May 2, 3 or 4 from 2 hours after low to 3 hours after high and motor up and down through the swatchway so you can collect the data. The downside will be you will be in a motorboat, the upside is you will stay dry and get home whatever the wind direction. Draft 1m.

    Www.solocoastalsailing.co.uk

  9. #9
    Join Date
    Nov 2002
    Location
    West Mersea
    Posts
    6,345

    Default Re: SW Sunk swatchway

    Quote Originally Posted by Plum View Post
    I can't help with the nmea/rs232 data but i can provide a bit of good humour and a ride out from Bridgemarsh Marina on May 2, 3 or 4 from 2 hours after low to 3 hours after high and motor up and down through the swatchway so you can collect the data. The downside will be you will be in a motorboat, the upside is you will stay dry and get home whatever the wind direction. Draft 1m.

    Www.solocoastalsailing.co.uk
    Some odd questions

    1. Dare I ask which plotter you use?
    2. Do you have a vertical stanchion - 1" dia?
    3. Do you have a 12v bayonet power source?

    Enormously happy in the dry. Gosh yes. Perhaps this is the time for me to confess: I now have a motorboat as well as TG, Intended, inter alia, to facilitate the surveys and to be dry. But both are ashore and I'm in the queue and it looks rather long.

    Fri 3rd we have a dinner arrangement, Sat 4th, we are at the Theatre, both evening jobs of course.
    www.crossingthethamesestuary.com

  10. #10
    Join Date
    Jun 2001
    Location
    UK East Coast
    Posts
    1,767

    Default Re: SW Sunk swatchway

    Quote Originally Posted by tillergirl View Post
    Some odd questions

    1. Dare I ask which plotter you use?
    2. Do you have a vertical stanchion - 1" dia?
    3. Do you have a 12v bayonet power source?

    Enormously happy in the dry. Gosh yes. Perhaps this is the time for me to confess: I now have a motorboat as well as TG, Intended, inter alia, to facilitate the surveys and to be dry. But both are ashore and I'm in the queue and it looks rather long.

    Fri 3rd we have a dinner arrangement, Sat 4th, we are at the Theatre, both evening jobs of course.
    I use an Android tablet running Marine Navigator and VMH admarilty charts.
    Yes, a short 150mm high 1inch vertical just ahead of transom
    I have 12v cigar type socket

    You can come over and test equipment on boat one evening beforehand.

    Www.solocoastalsailing.co.uk

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