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Thread: Singlehanded "Anything Goes" North Bay Sailing Instructions Posted

  1. #11
    Join Date
    Dec 2022
    Posts
    147

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    Jonathan I think your chart is perfectly accurate --- if you're moving a 1600 ton vessel, bla, bla, bla, that is a regulated navigation area.

    The problem is figuring out what the restriction actually is. I'm reading CFRs and manually plotting points for that, so it's not like I have a good system.

    What I do have is a free system that puts me firmly in control if I'm willing to do a lot of work:
    * I grab the ENC vector charts directly from NOAA.
    * I pull the specific layers I want into a free Geographic Information System (GIS) tool. I used to use GRASS, but switched to qGISa few years ago.
    * I then putz around in GIS and read the specs for the S-57 format to figure out what I'm looking at in the raw ENC.

    To show a little of what that looks like, here's the US5CA31M chart, showing the usual layers I use, with my usual formatting:
    Name:  US5CA31M_basic.png
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    Regulated areas are the RESARE layer in the S-57 spec, so importing that for US5CA31M shows
    Name:  US5CA31M_resare_basic.png
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    Oh, look, the whole bay is a regulated area.

    Fiddling in gQIS to color code by RCID we can see the boundaries of each area:
    Name:  USCA5CA31M_resare_colored.png
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Size:  144.3 KB

    I know that doesn't look like it did anything, but what we're seeing is that one area, in blue, is the whole bay and it may be covering other areas. So we can use the power of qGIS to hide the blue polygon, RCID 3870:
    Name:  US5CA31M_resare_colored_2.png
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Size:  191.4 KB

    I'm going to ignore the blue area --- someone else can make a trivia contest question about what the restriction is for that.

    Moving right along, there's two areas here, in purple and gold-ish. Looking in the attribute table, or labeling them with the INFORM column (per the S-57 spec), we can see the CFR numbers:
    Name:  US5CA31M_resare_with_CFR.png
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Size:  160.3 KB

    And then I have to read the CFR to figure out what the restricted area actually means -- and for CFRs that call out multiple areas, as 33 CFR 165.1181 does, I have then generated my own polygons to know what sub-part is what. See earlier discussion.

    It's a little work, but if I can make slightly better races for the SSS members because of it, a little work is worthwhile.

    But I would not recommend it for the casual SSS racer. I'm sure Navionics is far, far more friendly.

    Richard, 2023 SSS Race Co-Chair.
    Last edited by fauxboat; 04-20-2023 at 08:56 PM.

  2. #12
    Join Date
    Dec 2022
    Posts
    147

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    I should add, the downside to doing all this is that I have probably formed an unrealistic impression of how easy or hard it is to go find buoys, when given the official buoy name and light list number.

    Is that not available in navionics, perhaps by clicking on some likely suspects? Other boat-owner chartplotter tools?

    For that matter, do people still use the paper charts NOAA is phasing out? PDF charts?

    Richard, 2023 SSS Race Co-Chair

  3. #13
    Join Date
    Jan 2008
    Location
    Santa Rosa
    Posts
    644

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    Have you thought about running all these charts and description by the Coast Guard Permit Office? Pat Broderick

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