The Modern Navigation Trap

[colemj]

Non-sequitars always confuse me. How many rock jetties do you find in isolated cays? How many rocks do you need a chart to prevent hitting when out dinghying? Do you not expect any other fire-starting materials to be available when you are in your "real" survival conditions that you find yourself in every few days?

BTW, my waterproof handheld that also fits in my pocket allows me to sit right on top of a rock and draw the exact position on it. Using the battery in it, I can start a fire without matches when I am "really" surviving. Can't do that with a wet chart.

Mark

[noelex 77]

The advantage of radar is that it will show all the above surface chart errors even if you have never seen the anchorage/port/location before.

Traditional navigational techniques are much better than relying on GPS alone, but don't dismiss radar. As someone much more eloquent than me said it is the "killer app" for this sort of problem.

Not all boats can afford the cost and power consumption of radar and it is certainly not essential, but it is useful.

[wdkester]

I thought I might mention another tool for checking map accuracy in remote places, Google Earth.

When we were doing the Online DMA chart project (cancelled when we were told it was illegal) I would check the coast outlines against GE. Many charts were different by significant amounts. One doesn't know whether GE is wrong or the chart is wrong; but you do know to be cautious in this area.

In areas where I had reliable waypoints, I only found one area where GE was off (someplace in the Bahamas) and they have since corrected it.

GE, of course, doesn't give depths; but neither does radar. GE does allow you to plan ahead.

[noelex 77]

GE is a great source of information when entering a deserted, poorly charted anchorage.

Using all the available data is sound seamanship. Some relative weight and caution needs to applied. The traditional view of using only "official" charts is often less than optimum.

[Andrew Troup]

Thanks for all the thoughtful stuff in this thread, and it's great to see considerably less than the usual unhelpful fussing and fighting between proponents of convenience and proponents of efficacy.

As regards correcting erroneous chart info, it strikes me that this needs a bit more discussion and thought.

Those who favour a paperless nav station typically promote multiple redundancy (carrying multiple devices, using multiple types of electronic charts) in consideration of the volatility of electronic data.

This is also a favoured remedy to address various shortcomings of individual datasets, and styles of portrayal. (I personally feel uneasy about this, but that's another topic.)

I think it's worth reflecting on several ways this multiple-source nod in the direction of efficacy can extract a cost in convenience, if we are not careful.

One question is this: which dataset do you correct when you find an uncharted or mis-charted danger? And to what extent is that correction itself volatile?

A prudent mariner would correct all onboard data sources. In a perfect world each volatile data source would also be backed up an offsite location. Not to do the first of these things involves the risk that you might find yourself using the wrong dataset at some future date.

But that is starting to look like a serious amount of work, digging out all the various devices and data backups, and reacquainting oneself with how to make a permanent correction on each particular platform.

If you always use the same dataset, there is a risk attached to your resulting unfamiliarity with the alternatives, if access to that primary dataset is lost (which is clearly a strong possibility, otherwise why would anyone carry multiple alternatives?)

I reckon it is generally better to use a poor tool you're familiar with and whose shortcomings you can work around, than a good tool you don't fully understand, and whose more esoteric capabilities you are unable to command.

If I was running a paperless navigation station, I think (on superficial reflection) I would actually correct only one dataset, the one most commonly used, but I would also note all corrections in a durable notebook with waterproof pages. (Purists could instance the plastic nature of the pages to rebut accusations that their operation was no longer strictly 'paperless')

I would refer to this when using any but the 'master' dataset, and treat it as the durable, lifetime record of brushes with the dark side. I would keep it with my passport, and cherish it for all time.

[conachair]

Originally Posted by noelex 77

GE is a great source of information when entering a deserted, poorly charted anchorage.

Using all the available data is sound seamanship. Some relative weight and caution needs to applied. The traditional view of using only "official" charts is often less than optimum.

Agree completely, somewhat frowned upon but attitudes seem to be changing. GE can be a very useful source of nav info.

[darylat8750]

"If I was running a paperless navigation station, I think (on superficial reflection) I would actually correct only one dataset, the one most commonly used, but I would also note all corrections in a durable notebook with waterproof pages. (Purists could instance the plastic nature of the pages to rebut accusations that their operation was no longer strictly 'paperless')"

On my 3 systems very seldom are all three wrong in the US. ( Mexico is another story.) And if I may enter the affected area again I correct on the chart (s) that are incorrect. In Georgian Bay one chart had Pig Island and Sew Island. The other two had Pig Island and Sow Island. All three charts had the rocks in the right place. I didn't bother to change the name. I agree that familiarity with the systems is a requirement and a couple of hours of re acquaintance with the systems after a several month layoff is required for me. But then if I was still planning with paper it required as much time laying courses anyway. I really like laying Google Earth on top of a chart when internet is available. I've yet to see GE to be wrong. I really would like a forward looking sonar. Maybe someday when it gets a little less expensive.

[Littlechay]

What they all said about radar being your friend

[Oceanride007]

Last time I saw a commercial skippers standing orders, it read something like, "In sight of land always use coastal fix". Mind you on that vessel they had a interesting story to tell, when in one of the Gulf wars, the GPS had a bit of adjustment added to it, and although confusing I bet they were grateful to follow standing orders.
I suggest use coastal nav techniques closer to land.

[fryewe]

Coastal navigation techniques are commonly called piloting.

Near shore waters are commonly called piloting waters (waters where land features can be used to fix the boat's position).

When in piloting waters...pilot. Use GPS and radar as tools in piloting. In reduced visibility they may be the primary tools. In good visibility they may be backups. Piloting can be done on either paper or electronic charts.

The prudent mariner uses all means at his disposal to fix the boat's position to keep it safe...(I think I heard someone say once...or a thousand times...)

[captain58sailin]

I agree fryewe. Use all the tools in the box, including your brain, and senses, smell is always a good one near land. Hearing is a good one everywhere. I have used both disciplines Electronic & Paper for ocean crossings, and believe a combination of both is a good thing. I like paper because I am old school, I also like GPS, because I recognize it as a useful tool for navigation, but neither is the answer in all situations. There is no "one size fits all" answer to this equation. What works best for the individual and what gets the desired results is the right answer. Opinions are like noses everyone has one and they all smell.

[valhalla360]

Originally Posted by conachair

Agree completely, somewhat frowned upon but attitudes seem to be changing. GE can be a very useful source of nav info.

Love GE as a backup. The only problem is there isn't a simple way to download an area. In populated areas, you can turn on the internet card in a pinch but for regular use, it eats up a ton of data plan usage and in isolated areas where it's more useful, cell coverage tends to be poor.

There are some after market programs but the ones I've tried are a pain to use.

[wdkester]

You can make copies of the GE cache.

1. Bring up GE and Clear the cache.
2. Traverse the area of interest at the appropriate altitude(s).
3. Exit GE
4. WIN 7 - GE cache is found in C:\Users\{username}\AppData\LocalLow\Google\Google Earth

Copy the following 3 files to a folder
dbCache.dat
dbCache.dat.index
dbroot_cache

5. When you are away from wifi copy these files into the GE folder, bring up GE, and you are set.

Some cautions:
GE changes the file format occasionally, thus destroying your tedious work.

You should set the Cachfile size to the max limit.

You will need to keep an eye on the cache file and save it when it nears the limit. It ovewrites the oldest data.

I have saved the entire ICWW and I think it took 10 or so caches. Unfortunately they have changed the format since; but I got to use it for my last trip down.

[Heart of Gold]

Mainebristol, an excellent discussion, Thanks for this.

[valhalla360]

Originally Posted by wdkester

You can make copies of the GE cache.

1. Bring up GE and Clear the cache.
2. Traverse the area of interest at the appropriate altitude(s).
3. Exit GE
4. WIN 7 - GE cache is found in C:\Users\{username}\AppData\LocalLow\Google\Google Earth

Copy the following 3 files to a folder
dbCache.dat
dbCache.dat.index
dbroot_cache

5. When you are away from wifi copy these files into the GE folder, bring up GE, and you are set.

Some cautions:
GE changes the file format occasionally, thus destroying your tedious work.

You should set the Cachfile size to the max limit.

You will need to keep an eye on the cache file and save it when it nears the limit. It ovewrites the oldest data.

I have saved the entire ICWW and I think it took 10 or so caches. Unfortunately they have changed the format since; but I got to use it for my last trip down.

As I said, there isn't a simple way to save a significant area for offline use.