Trust your eyes, not the GPS - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
 Not a Member? 

Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


Reply
 
LinkBack Thread Tools
  #11  
Old 12-30-2009
Senior Member
 
Join Date: Jun 2006
Posts: 4,998
Thanks: 5
Thanked 18 Times in 18 Posts
Rep Power: 11
wind_magic has a spectacular aura about wind_magic has a spectacular aura about wind_magic has a spectacular aura about
GPS is great for getting a position fix, an electronic version of celestial, it gives very accurate fixes.

Charts (datum, projections, updating, accounting for errors, etc), using fixed lights and light lists, sounds and sound signaling (horns, etc), compasses (and correction), dead reckoning, piloting (soundings, turning, logs, bearings), reading shoals and banks, fog, tides, currents, radar (reflection, refraction, ranging, echos), route planning, celestial (sights, reduction, time keeping, sextant use and maintenance), sailings, keeping watches, voyage plans, ocean state (waves, currents, ice), weather (reports, forecasting, routing, etc), weather monitoring (pressure, humidity, etc), etc, ... all that pesky stuff that goes under the heading "navigation", all of that stuff remains relatively unaffected by the fact that we can get a very accurate fix from a GPS receiver. In fact, Bowditch, the 800+ page "The American Practical Navigator" devotes precious (even worrisome) few pages to using GPS to get a very accurate fix. Said another way, knowing where you are at has very little to do with whether you are about to be run over by a freighter in the fog, or be swept on to a lee shore because the wind is clocking ...
__________________
What are you pretending not to know ?

Please support my
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by wind_magic; 12-30-2009 at 11:15 AM. Reason: sp
Reply With Quote Share with Facebook
  #12  
Old 12-30-2009
BubbleheadMd's Avatar
Chastened
 
Join Date: Nov 2009
Location: Edgewater/Annapolis
Posts: 2,836
Thanks: 0
Thanked 54 Times in 50 Posts
Rep Power: 5
BubbleheadMd will become famous soon enough
Send a message via Yahoo to BubbleheadMd
This is outrageous. I spend hard currency on these devices to relieve my of the burden and responsibility of thinking for myself. Now I find out that they aren't 100% accurate, 100% of the time and they don't even warn me when I'm about to do something stupid?

I demand a refund and an apology.
Reply With Quote Share with Facebook
  #13  
Old 12-30-2009
AE28's Avatar
NON member
 
Join Date: Jun 2008
Posts: 546
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
AE28 is on a distinguished road
In another published report about the couple stuck off-road in Oregon, a law enforcement officer was quoted as saying their GPS was set up to show the shortest route.

I have almost no experience with GPS on the water but use one quite a bit for routing on land.

I still haven't read a report of their GPS malfunctioning, so I'll continue thinking the couple screwed up.

Paul
Reply With Quote Share with Facebook
  #14  
Old 12-30-2009
canadianseamonkey's Avatar
Caribbean Surveyor
 
Join Date: Sep 2006
Location: Now in Sosua, DR
Posts: 511
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
canadianseamonkey is on a distinguished road
My GPS saved me from grounding a few years ago while sailing in the fog. There's a time to use your eyes and brain, but technology is often relied upon.
Reply With Quote Share with Facebook
  #15  
Old 12-30-2009
Boasun's Avatar
Senior Member
 
Join Date: Feb 2007
Location: New Orleans, LA
Posts: 3,063
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 9
Boasun will become famous soon enough Boasun will become famous soon enough
Quote:
Originally Posted by padean View Post
This thread reminds me of a recent thread froma husband/wife team navigating into a new channel/port with the wife at the wheel and the husband down below calling out directions by looking at the chart plotter...

While chart plotters are a very nice navigation assistant, in close waters they do not replace two pair of eyes, one at the helm, one on the bow watching the water for obstructions.

I personally rely more on accurate maps, and use GPS primarily to help me with location of the boat, rather than navigation per se, except in deep water over long stretches. I have seen several unhappy boaters who thought GPS was a good alternative to eyesight in fog and paid for their mistake. Rarely would I use the GPS when going up a river or into a narrow channel. That is what all the channel markers are for, and even the best GPS maps don't account for local variation.

A good sailor uses all available tools for navigation aids - this ALWAYS includes eyes and maps, usually includes GPS, sometimes radar. The more accurate and up to date the input, the more sure the course....
Seeing that "MAPS" are for land, such as roads, political enities, (towns, counties, etc.) and so forth. Such as what highway to take from your town to the next.

I prefer CHARTS for Water ways and coastal transits. Charts are for Navigators who want to know the channels, depths of waters and Navigational Aids, Navigational hazards and so forth...

I have my students bring in donuts everytime they make this mistake... Yah! I've put on weight.

Do you see the difference?
Do you understand the difference?
GPS is a good tool. But you should never rely 100% on it. Practice your Coast piloting, your celestrial (sextant required) and plot your course on a paper chart if you have them. With Guests on board or the Kids get them involved in Navigation. You will learn more and become comfortable in your skills while teaching others a new skill.
__________________
1600 Ton Master, 2nd Mate Unlimited Tonnage

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Maritime Instructor
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

S/V Rapture

Last edited by Boasun; 12-30-2009 at 12:22 PM.
Reply With Quote Share with Facebook
  #16  
Old 12-30-2009
MC1 MC1 is offline
Senior Member
 
Join Date: Jan 2008
Location: Lake Ontario
Posts: 277
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
MC1 is on a distinguished road
GPS has resulted in significant safety improvements in aviation where it's used in highly complicated and risky situations such as commercial airliners shooting instrument approaches in near zero visibility at congested airports.

How is this possible given the issues we're seeing with GPS usage for marine and land navigation? A couple critical differences:
1. Aviation GPS maps are specifically maintained and certified for navigation use
2. Pilots are legally required to have current map information loaded into their GPS units if they are being used for navigation
3. GPS equipment must be certified for specific uses (e.g., instrument approaches, enroute, Visual Flight Rules only)
4. Pilots working in poor weather conditions have significant other ground based support (i.e., control tower vectoring, radar services, etc.)

Until maine GPS units and maps are certified for specific marine navigational uses, they should only be thought of as helpful backups. We know they can help us stay out of trouble, but they can also get us into it if we trust them beyond their limitations.

The current situation where a combination of up to date and out of date (and sometimes very out of date) map information has now been converted into electronic form and loaded into GPS units that are highly accurate w.r.t. your position, creates a false sense of security for users that are not fully aware of the limitations.

I feel there's so much reliance now on GPS for marine use that there needs to be a more concerted effort to correct out of date mapping information, and also to make it more obvious to users when the maps they are using are presenting information that has not been recently verified. The maps may show when depth soundings were taken for example, but often times this doesn't get displayed clearly, and/or users are not paying any attention to the significance of this information.

It seems we need a better process for providing feedback to the map information source providers (e.g., US gvmt) when errors are found, and for them to be able to update and diseminate the information quicker. Maybe industry GPS leaders such as Garmin should be doing more to lobby for this. How can we get them to do that? Hold them at least partially accountable when information from their devices assists us in getting into trouble? Yes, as captains, we're ultimately responsible for our own navigation, but we also need to do something to presure suppliers to give us better quality information. They're making money on this after all.

As a manager once told me, "you deserve what you tolerate". Should we stop tolerating out of date and unverified mapping information being given to us and respectfully demand an improvement to the status quo?

Last edited by MC1; 12-30-2009 at 02:12 PM. Reason: (correction)
Reply With Quote Share with Facebook
  #17  
Old 12-30-2009
jackdale's Avatar
Senior Member
 
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 8,833
Thanks: 26
Thanked 36 Times in 33 Posts
Rep Power: 6
jackdale will become famous soon enough
MC1 reminded me of another issue with vector charts in chartplotters. They may not scan the data from the original sources correctly. Just south of Victoria BC harbour is a military exercise area WK, whiskey kilo. On at least one chartplotter that I have used, it shows as a "wreck."

I have not looked closely to see what other discrepancies exist.
__________________
__________________
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)
Reply With Quote Share with Facebook
  #18  
Old 12-30-2009
eherlihy's Avatar
Learning the HARD way...
 
Join Date: Jan 2007
Location: Boston Area
Posts: 3,458
Thanks: 107
Thanked 56 Times in 55 Posts
Rep Power: 8
eherlihy will become famous soon enough
GPS is an AID, not a Navigator

My wife bought a new car this past summer. It came with XM radio, and a fancy DVD/NAV package built in to the dash. The other day I tried the DVD player for the first time and found that it doesn't work with the engine running . What a POS - I would understand if it shutoff in D or R; but engine on = no DVD, engine off = no heat/AC!

Anyhoo, we've used the GPS many times to bring us hither and yon, and I like to have the map displayed to add to my situational awareness. The same day mentioned above we headed over to my brother-in-law's house (I was trying the DVD while waiting for the admiral to come out of the house - per usual ) and the GPS showed us CONSISTENTLY about 1/2 mile off the road (to the south) but paralleling it. It was a cloudy day, but the GPS indicated that it had a strong fix on more than 4 satellites. I tried everything, short of shutting off the car, that I could think of to re-boot the unit, hoping that it would correct the problem, to no avail.

I'm glad that I wasn't using this unit to navigate an unfamiliar channel!

GPS is an AID to; and not a substitute for, good navigational skills!
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

USCG Licensed OUPV Captain, ASA 101/103/104/105 Certified Instructor - Also certified in Recreational Marine Electrical Systems


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Getting back onto the water after undergoing knee surgery.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by eherlihy; 12-30-2009 at 03:27 PM. Reason: WOHOO!! Post 600 for me!!
Reply With Quote Share with Facebook
  #19  
Old 12-30-2009
Senior Member
 
Join Date: Jun 2006
Posts: 4,998
Thanks: 5
Thanked 18 Times in 18 Posts
Rep Power: 11
wind_magic has a spectacular aura about wind_magic has a spectacular aura about wind_magic has a spectacular aura about
Quote:
Originally Posted by MC1 View Post
I feel there's so much reliance now on GPS for marine use that there needs to be a more concerted effort to correct out of date mapping information, and also to make it more obvious to users when the maps they are using are presenting information that has not been recently verified. The maps may show when depth soundings were taken for example, but often times this doesn't get displayed clearly, and/or users are not paying any attention to the significance of this information.
My vote is that they put all the chart information into categories, and the worst categories of charts can only be displayed on GPS units as children's crayon drawings. That would let people know that they should use the information with a little more caution than what we hope will someday be certified charts.

MC1 is right, part of the reason for the problem is that those computer vectored edges are so crisp and clear, they just must be right! People don't even think about the datum, when they were updated, etc.
__________________
What are you pretending not to know ?

Please support my
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by wind_magic; 12-30-2009 at 03:09 PM. Reason: sp
Reply With Quote Share with Facebook
  #20  
Old 12-30-2009
eherlihy's Avatar
Learning the HARD way...
 
Join Date: Jan 2007
Location: Boston Area
Posts: 3,458
Thanks: 107
Thanked 56 Times in 55 Posts
Rep Power: 8
eherlihy will become famous soon enough
I took a week long cruise with a friend this past summer. He and I own the same portable GPS/Chartplotter unit (Garmin GPSmap478). I showed him how I use the unit, which varies from his former technique. I believe that he now uses it as I do. Assuming that you're interested, here is what I do:

First, I get a chart and figure out where I'm heading for the day. I mark the start point, the end point, and figure out a way of getting from one to the other without crossing rocks, ATON, or the yellow and green parts of the chart. Ideally, I like to stay in the white.

Once the plan is complete, I start out. I use the GPS to confirm where I think I am as I head out of the harbor. Once outside the harbor, I use the rocker switch to point to a random spot, where I think that I may have to do something (like change heading, look for a buoy, enter a harbor, etc.) along my intended path (already marked on the chart) on the chartplotter. In effect, as I move the cursor ahead of my current position on the chart I am verifying that the chartplotter matches my chart (and I haven't missed anything). I then navigate to the random point, using the chartplotter as an aid. Once I arrive at the random point, I repeat the process to another random point along my path.

I do NOT enter a detailed series of waypoints to bring me from start to finish and use the navigate route feature to guide me through them. I believe that this: a- takes too long given the input medium (rocker switches), b- if I missed an obstruction between waypoint x and waypoint y, I'm in trouble, and I won't know it until it is too late.
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Handheld GPS Overview Tom Wood Seamanship Articles 0 05-31-2001 08:00 PM
GPS Gets More Accuracy Jim Sexton Seamanship Articles 0 05-21-2000 08:00 PM
GPS Gets More Accuracy Jim Sexton Gear and Maintenance Articles 0 05-21-2000 08:00 PM
GPS Gets More Accuracy Jim Sexton Cruising Articles 0 05-21-2000 08:00 PM
Advanced GPS Interfacing Jim Sexton Gear and Maintenance Articles 0 10-07-1999 08:00 PM


All times are GMT -4. The time now is 09:51 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.