"Capt. Mooron" wrote :
Try not to talk down to someone that has spent time in cartography Jeff.
Why not? You talk down to everyone!
With an expected accuracy of 50 feet max... a GPS is accurate enough but not
pin point. I believe I stated it should be used in conjunction with a chart
and not as a stand alone based on waypoint data not verified to the chart
datum. If you have a chart whose GPS Data puts you aground by 100 feet...
you are either using errata datum or your chart is ****ed.
Yes - that's the point - there are still such charts out there!
Do you have any
comprehension of the sphere labeled as "sea level" and the fact it's
actually a not actually perfectly spherical?
Try not to talk down to someone who spent many years programming spacecraft navigation for
NASA. Geodesy was not my specialty, but I'm not unfamiliar with the basics. Is there a
point to this, or are you just being jaxian?
You want to really converse on the specifics of GPS with someone that has
utilized it for data triangulation. I have targeted data over a 48 hour
period based on surveyed benchmarks that clearly illustrates the accuracy
expected at differing latitudes and altitudes. It looks like a shot gun
pattern at 20 meters.[s/a off] I can still give you the error ratio for your
chart with 3 separate fixes confirmed and verified by alternate sources.
Now you're really sounding like Jax. Well, OK, Jax would have claimed he had an expert
friend that did it.
A correctly configured GPS is a great tool...... when used by knowledgeable
people and proper charts.
I'm not saying it isn't a great tool - but every now and then it can lead one astray, or
give one a false sense of security. Not every chart is perfect, and not every channel
stays where its supposed to.
--
-jeff
"Constant Vigilance!" - Frances W. Wright
CM
You can rely on a GPS to provide very usable data once you ascertain it's
accuracy on a chart by comparative data. Once that is established... you
should be well aware of your coordinates
"Jeff Morris" jeffmo@NoSpam-sv-lokiDOTcom wrote in message
...
| Its not that the ICW is poorly charted, its that the chart only has to be
off by 100 feet
| to put you on land. Its possible that the last time through SA was turned
on for a while,
| but I really had the feeling that several of the charts I was using was
simply displaced
| by 100 feet of so. So how often do you think the creeks in Georgia get
re-surveyed?
|
| For an article on the errors in Bimini, see:
| http://www.bluewaterweb.com/news/9-01gps.htm
|
| Your comments are inconsistent - first you say GPS "should never be relied
on as sole
| source" but you claim that you don't agree with "You should not rely on a
GPS when using a
| chart."
|
| Seems to me that you just like to argue and you don't care whether you
make any sense. At
| least Neal sticks to one position, albeit usually wrong.
|
|
| --
| -jeff
| "Constant Vigilance!" - Frances W. Wright
|
| "Capt. Mooron" wrote in message
| ...
| First off it's difficult to believe that any stretches of the ICW are
poorly
| charted. I'm not a big proponent of GPS accuracy... I do concur with
Jon's
| assertion that it's a tool... it has it's limits and should never be
relied
| on as sole source for navigation. That being said... I've seen
supposedly
| competent sailors use default datum or operate in 3D fix modes. What I
don't
| agree with is ...
|
| A]- "You should not rely on a GPS when using a chart"
| That position would have you question your radar, sonar, chronograph and
| compasses.. never mind the plotting tools!
|
| B]- "It tells you nothing about your actual position relative to actual
| obstructions"
|
| It does indeed confirm a fix if you have a chart..... so does radar.
|
| C]- "Charts are notoriously inaccurate and don't match long/lat info
|
| P-l-l-u-u-u-u-e-e-e-e-z-z-z-z-e-e-e...... they certainly are Not!.
| Especially if
| you can read one, verify fixes and have the latest datum.
|
| CM
|
|
|
|
|
|
| "Jeff Morris" jeffmo@NoSpam-sv-lokiDOTcom wrote in message
| ...
| | Jon has a point. There are certain locations that are notoriously
poorly
| charted,
| | datum-wise. The ChartKit I have for the Bahamas is way off. I also
| found that for long
| | stretches of the ICW, my charted position was on dry land.
| |
| | For most of where I sail, however, the GPS and the chart agree to a
boat
| length or better.
| |
| |
| | "Capt. Mooron" wrote in message
| | ...
| | Were did you dig up this crap Jon??? Learn how to enter correct
datum
| and
| | save yourself further embarrassment.
| |
| | It's a good thing both you and Neal sail in protected waters with
line
| of
| | sight navigation or there would be a lot less boats around.
| |
| | CM
| |
| | "Jonathan Ganz" wrote in message
| | ...
| | | You should not rely on a GPS when using a chart. It's a tool
| | | only. It tells you nothing about your actual position relative to
| | | actual obstructions. Charts are notoriously inaccurate and
| | | don't match long/lat info.
| | |
| | | "Simple Simon" wrote in message
| | | ...
| | | And, good morning to you, sir!
| | |
| | | With the advent of GPS and its accurate nature, plotting your
| | | position on a chart is a more accurate method than using
| | | depth readings and dead reckoning. It's that simple.
| | |
| | | S.Simon
| | |
| | |
| | | "Thom Stewart" wrote in message
| | | ...
| | | Good Morning Simple,
| | |
| | | Many of us SAILORS that sail among Whales use charts and depth
| finders
| | | to get a location of exactly where we are on the chart. This
is an
| | | accepted practest in DED piloting.
| | |
| | | We finally got a nice cleaning rain last night and we have
about
| 5mph
| | | wind at the house here. Waiting for my dog to wake up. We'll
| | probabilly
| | | spend the day out on the water. The Pilothouse will come into
| play.
| | Nice
| | | and dry and warm.
| | |
| | | OT
| | |
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