What confidence do you have in your charts?

[MicHughV]

Paper charts come in a variety of different scales, which may limit the detailed information you may need, depending on which chart(s) you have.
Some electronic charts suffer the same lack of detail. I have electronic charts that show my boat position over land or crossing a shoal, where no shoal exists, etc.

You should read charts with a smidge of common sense. Terrain changes, depth changes, shoals appear out of nowhere, etc, etc.
It's good idea to keep a cruising guide handy of the place you intend to go as these invariable depict more " local" knowledge.

A pet peeve of mine, is that the modern day sailor has his/her eyes peeled to that magic marvel at the pedestal, instead of keeping an eye out to where the boat is headed.

[rslifkin]

Originally Posted by MicHughV

A pet peeve of mine, is that the modern day sailor has his/her eyes peeled to that magic marvel at the pedestal, instead of keeping an eye out to where the boat is headed.

I've never quite understood this mode of operation, short of running in weather where you can't see any useful distance outside anyway, so heads-down running by radar, AIS, and charts is the best you've got. In good weather, the chartplotter is there for an occasional check of "still on course?" and "what's coming next?" or "what buoys and land should I be expecting to see up ahead?"

[Benz]

Originally Posted by RaymondR

You'll end up confused.

A graticule is how Cartesian coordinates are represented on a sphere.

A grid how they are on a flat plane. Land maps of relatively small areas, such as UTM system, are presented on a grid.

We are not talking about land maps here, nor does the UTM grid enter into marine navigation.

[RaymondR]

Originally Posted by Benz

We are not talking about land maps here, nor does the UTM grid enter into marine navigation.

I was using it as an example of where the grid system of coordinates is used Ben.

And you never know, a knowledge of the various systems might come in handy some day.

The Great Barrier Reef marine park is divided into zones which define the allowable activities for each zone. From the coordinates used to define the boundaries it is quiet obvious that the government bureaucrats, with their land mapping mindsets, used UTM coordinates when drafting the boundaries, then converted them into graticular coordinates.

A fisherman taken to court in Cairns was able to successfully argue to a judge that since he was alleged to have been caught on a zone boundary when the alleged infringement occurred and that there was no exact way to transfer the coordinates between the graticular and grid systems the government could not reliably prove that he was inside the subject zone when the alleged infringement occurred. The judge ruled no case to answer on that basis.

[MicHughV]

People used to find their way around the world with a sextant and a lead line without too much trouble.
In my day, charts were very expensive, and to get each and every chart you needed was cost prohibitive.
Like others, I "traced" charts I borrowed from other cruisers that I needed and did not have. Still have 'em today.
Electronic charts were still a figment of the imagination back then, but most sailors of the day seemed to do just fine.

[Networker]

I have confidence, they know more than me in the well traveled areas.

In the less well travelled area; Relying on satellite photos, dinghy and lead line, as well as hand held depth finder. But for the most part, they’re a good starting point and eyes and sensors to ground truth it all.

[Networker]

Nice idea on tracing the charts, that makes sense.

[Benz]

Originally Posted by RaymondR

I was using it as an example of where the grid system of coordinates is used Ben.

And you never know, a knowledge of the various systems might come in handy some day.

The Great Barrier Reef marine park is divided into zones which define the allowable activities for each zone. From the coordinates used to define the boundaries it is quiet obvious that the government bureaucrats, with their land mapping mindsets, used UTM coordinates when drafting the boundaries, then converted them into graticular coordinates.

A fisherman taken to court in Cairns was able to successfully argue to a judge that since he was alleged to have been caught on a zone boundary when the alleged infringement occurred and that there was no exact way to transfer the coordinates between the graticular and grid systems the government could not reliably prove that he was inside the subject zone when the alleged infringement occurred. The judge ruled no case to answer on that basis.

Sooo, why is "graticule" a confusing word, as you claimed?
And doesn't your story prove my point that UTM is useless for marine navigation?

[boatman61]

Originally Posted by Networker

Nice idea on tracing the charts, that makes sense.

I used to get them copied in black and white back in the 80's, 90's.. then coloured them in during periods of boredom.

[MicHughV]

True, many of my tracings were done from black and white copies of the original. I also colored them in, some were.....er...quite "artistic"..

[MicHughV]

True, many of my tracings were done from black and white copies made from the original.
I colored mine.....er....in an " artistic" manner, priceless examples....should be in an art gallery somewhere..

[wyb2]

Originally Posted by MicHughV

Electronic charts were still a figment of the imagination back then, but most sailors of the day seemed to do just fine.

Except for the ones that ran aground and died. But yeah, other than that, they did great.

[RaymondR]

Originally Posted by Benz

Sooo, why is "graticule" a confusing word, as you claimed?
And doesn't your story prove my point that UTM is useless for marine navigation?

One does not want to confuse oneself if one happens to be one of those folks who indulges oneself in both land and marine navigation.

For example if one had been carrying out surveys on land using maps compiled using the UTM system there is no problem with using either the northings or eastings to measure off the distance between two points. However if one uses the latitude scale on a mercator projection to do the same error will result.

Whilst you may think that UTM is useless the bureaucrats who charted to zones did not and many boundaries are displayed in degrees, minutes and decimal minutes to three decimal places, which is a nuisance and they should not have done it that way. I suspect that the zones were delineated by scientists (who hate any numbering systems not based on pure decimal and in particular the sexagesimal of the Babylonians)

[Benz]

Originally Posted by RaymondR

One does not want to confuse oneself if one happens to be one of those folks who indulges oneself in both land and marine navigation.

For example if one had been carrying out surveys on land using maps compiled using the UTM system there is no problem with using either the northings or eastings to measure off the distance between two points. However if one uses the latitude scale on a mercator projection to do the same error will result.

Whilst you may think that UTM is useless the bureaucrats who charted to zones did not and many boundaries are displayed in degrees, minutes and decimal minutes to three decimal places, which is a nuisance and they should not have done it that way. I suspect that the zones were delineated by scientists (who hate any numbering systems not based on pure decimal and in particular the sexagesimal of the Babylonians)

Once again, the only confusion was introduced by you. I used a word perfectly suited to the conversation--which was about marine navigation--and you went off on a weird tangent about grids and governments.

Do you navigate on both land and sea? I congratulate you. But here we are talking about marine navigation, and the word is only confusing to those so insecure in themselves they need to find fault with everything.

[requiem]

Originally Posted by RaymondR

The Great Barrier Reef marine park is divided into zones which define the allowable activities for each zone. From the coordinates used to define the boundaries it is quiet obvious that the government bureaucrats, with their land mapping mindsets, used UTM coordinates when drafting the boundaries, then converted them into graticular coordinates.

I am curious as to how you concluded they were based on UTM. As far as I understand it, conversion between UTM and lat/lon should be accurate down to a few millimeters, if not nanometers these days.

On the other hand, rounding differences between DDMM.mmm and DDMMSS.s formats could be in the range of a few meters. For a rough estimate using "a minute's a mile", 0.001’ would be ~1.85 metres, and 0.1” would be ~3.1 metres. (Rough since even the latitude scale varies, although sufficiently small enough that the approximation works.)

There's also the minor problem that Australia is a bit of a speed demon; it's hurtling northward at about 7 cm per year and I believe just a few years back there was a 1.8 m correction to re-sync the Australian datum with WGS84.