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Navigation - Paper Charts or Electronic Charts?

9/19/2017

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I've read a few sailing forums recently where people say "paper charts are unnecessary."
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As a commercial skipper who's worked internationally, a recreational sailor (circumnavigating the planet one-and-a-half times, plus many inland waterways), and maritime teacher, I'd like to explain why you shouldn't just rely on electronic equipment AND why it is prudent to have several options.
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Extract from Cruisers' AA (Accumulated Acumen):

GPS (Global Positioning System) - Errors

GPS contains errors and therefore your position should always be checked via other methods.
Errors that occur within the GPS unit:
  • Systematic: Some errors are caused by the changing satellite geometry. This is called Dilution of Precision (DOP). For a three-dimensional fix, you need four satellites. Ideally, one of the satellites should be directly overhead, with the other three separated by 120 degrees of azimuth. An arrangement other than this ideal situation will cause DOP inaccuracy. A good value of HDOP (Horizontal DOP) is between two and four, values in excess of this size are of poor accuracy - you can check the values on the GPS.
  • Environmental errors: Moisture and salt in the air, poor weather conditions or lightning.
  • Ionospheric delay: Signals from satellites bend on entering the ionosphere (aka refraction) and their speed varies. (The ionosphere is the outer region of the Earth's atmosphere).
  • Multipath error: A satellite signal may be reflected off the water, or off metal objects on board your vessel. This may cause the GPS receiver antenna to receive the signal by two or more paths.
  • Receiver errors: Mismatch of satellite signals.
  • Selective Availability: SA is the military’s ability to scramble the GPS readings. At the time of writing, the USA is not scrambling the signal (the SA was turned off in 2000). DGPS (Differential GPS) was developed to reduce SA.
 
Common errors in using the GPS:
  • Offset: The main position fixing error occurs when using the GPS in combination with older charts. The correct offset from the chart needs to be applied to the GPS reading (see ‘Chart Errors’ earlier in this section for full details).
  • Ensure your GPS settings match the spheroid of your chart. The GPS operates on a spheroid called World Geodetic Spheroid 84 (WGS84). In the past, charts have been based on various spheroids, e.g., Australian Geodetic Datum 1966 (AGD66): You must check your chart to find out whether it is based on WGS84 or AGD66 and set your GPS accordingly.
  • Magnetic or True: You can select Magnetic or True settings for bearings and courses. Ensure you have selected your preferred setting before completing these calculations. (See ‘True to Compass or Compass to True’ under Charts, earlier in this section.)
  • Measurements: Are you reading statute miles or nautical miles for distance? Check your unit is set to nautical miles.
  • Measurements: Are you reading knots for speed? Ensure your GPS is set correctly.
  • Measurements: To reduce errors, check your GPS is set to degrees, minutes and decimals of a minute instead of seconds - to match your charts.
  • Location: Follow the manufacturer’s instructions when mounting your GPS. Obstructions can affect the signal and the GPS unit can affect the ship’s compass.
  • Input Errors: Double check the co-ordinates that have been inputted into the GPS. Ask someone else to read and check the numbers too.
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​Electronic charts: are fantastic, but they can have errors. They are an aid to navigation and should not be completely relied upon. Use electronic charts in conjunction with paper charts. You could lose your electronic charts with a flat battery or lightning strike, but you won’t lose your paper charts this way.
Zooming right in to every area may reveal all reefs and obstructions. BUT not zooming in enough may hide them. (We used two version of electronic charts as a backup/double check - at times they were spot on, other times they were off by a worrying distance.
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Paper Chart Errors
Chart Errors: If you are using very old charts you may find that the GPS co-ordinates put you on an island. In this case, the GPS is more accurate than the chart. All positions will need to be offset by the amount given in the title of the chart. Every modern chart will have a note stating whether the GPS co-ordinates can be plotted directly or an offset is to be followed. This is a good example that, shows that you must check all the information provided on the chart very carefully.
 
For example (1): Chart AUS 252 Whitsunday Group. Under the chart title it states:
 SATELLITE DERIVED POSITIONS
Positions obtained from the Global Positioning System (GPS) in the WGS 1984 Datum can be plotted directly onto this chart.
 
Example 2: Chart AUS 802 Cape Liptrap to Cliffy Island, states:
 
Positions are related to the Australian Geodetic Datum (1966)
(see SATELLITE DERIVED POSITIONS Note).
 
Next to title it states:
 
SATELLITE DERIVED POSITIONS
Positions obtained from the Global Positioning System (GPS) in the WGS 1984 Datum must be moved 0.09 minutes SOUTHWARD and 0.08 minutes WESTWARD to agree with this chart.
 
 Making the corrections: In the case of chart AUS 802 the correction would be as follows:
 
GPS (WGS 1984) position
39° 00.00’ S
146° 15.00’ E

 + 0.09’ S
----------------
+ 0.08’ W
-----------------
 39° 00.09’ S
146° 14.92’ E
 
Corrections vary: Some South Pacific Island charts will note corrections that can be a nautical mile out! 
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Personally
I would not go to sea without paper charts and I'd certainly use electronic charts as well. However, understanding all the limitations of all types of charts, and GPS limitations is just as imperative as buying the right gear.

Oh, and I'd take a seaworthy vessel of course, too. (And a sextant).
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It's a Horse's Life!

9/1/2017

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Horses Rule Okay?

I treat my horses better than I treat myself.

In fact they have me pegged as their domestic servant, and I think they’ve nailed it.
 
Pedicures
They have a regular pedicure, performed by a professional. The closest I get to beauty treatment is discussing the possibility with the farrier.
 
“How much  does it cost for women to get a pedicure these days?” he asked while rasping at Charlie’s toes.
"No idea, the horses have one, I don't."
"Well I'll do one for you,"
he offers.
"I don't think your tools are up to the job!"
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Farriers file. Not sure it is strong enough for my nails!
Beauty Products
Years ago I painted one of my horses feet with Stokholm Tar. He was bare-foot (like ours are now), as he was terrified of being shod. Horses have nail varnish after pedicure. I’m lucky if my nails see a nailbrush once a week.

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Nourishment
The horses have all the food they need roaming 70 acres. Their menu consists of many different types of grass to fulfil all their dietary needs. They drink spring water from the creek.

We drink plastic tasting rain water from the new tank, which is sometimes smokey-flavoured when we've had the fire on and the smoke has 'flavoured' the roof (we catch all our own water).

As far as food is concerned, sometimes we find time to stuff two-minute noodles down our throats.
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More Beauty Treatment
The horses are groomed, mane and tails are combed, we scratch their itchy spots and they’ve even received a soft massage from Noel (he’s a trained masseur).
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It’s pretty rare for me to brush my hair more than once a week. That’s all I’ll say on that topic!
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Treats
Carrots are a big favourite here. They are regulated and only given after schooling as a reward. Our treat is a big Saturday where we may just manage to stay up to 8:30pm

Love
The horses receive pats, rub downs, plenty of praise and a lot of love.  They are told they are good – (particularly hard to do when Charlie takes twenty minutes to catch sometimes). Noel’s endearments to me are in the form of “pesky” or “nutcase”. And occasionally we’ll get to have a cuddle.
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Dental Treatment
I check their teeth and they are rasped when necessary.
There is no dentist for us unless we are in screaming agony and about to die of pain.

Healthcare
The boys receive appropriate jabs to maintain their health and well-being. The closest we’ve come to this is injecting coffee.
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Work
At the moment the horses are living a life of riley. Fortunately, our land is hilly and they enjoy a few good gallops each day. They walk many kilometres, up and down, selecting the best grazing each day.

When Noel is chopping wood for the fire, they stand in the sun and watch. When I’m using the Trimmer-on-Steroids (the Trimmer, not me!) to kill the bracken, they wander off to another part of grazing, quite put out that I am working where they want to eat.

Endearments and Encouragement
The boys are encouraged to try something new (I’ve just started in-hand schooling) – with lots of ‘good-boys’ and pats and 'you're so handsome!'

I can’t remember when I’ve said to Noel he looks nice, although I did tell him his hair needed a cut the other day.
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Yup, they’ve got it all – health, care, food, love, fun – regularly and top-notch stuff. Whereas I seem to stumble from one disaster to the next, with hunger pangs.
 
But their hoof-beats are my heart-beats, and I wouldn’t have it any other way.
Hoof Beats are my Heart Beats T-Shirt
Hoof Beats are my Heart Beats T-Shirt
by UnravelTravel
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Read more about our boys here - and our extraordinary journey together.

(Available in paperback, audio and kindle. If you'd like a paperback an live in Australia, let me know it's easier to purchase directly from me).

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