Trust your eyes, not the GPS - SailNet Community

   Search Sailnet:

 forums  store  

Quick Menu
Boat Reviews  
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Hatches and Portlights
Interior And Galley
Marine Electronics
Other Items
Plumbing and Pumps
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.

LinkBack Thread Tools
Old 12-30-2009
jackdale's Avatar
Senior Member
Join Date: Dec 2008
Location: Calgary, AB, Canada
Posts: 9,019
Thanks: 27
Thanked 56 Times in 53 Posts
Rep Power: 7
jackdale will become famous soon enough
Trust your eyes, not the GPS

I just saw this on one of our national news channels. I think it applies to boating as well.

CTV News | Couple stranded after GPS sends them down backwoods
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 Quick reply to this message Share with Facebook
Old 12-30-2009
tager's Avatar
Senior Member
Join Date: Nov 2008
Posts: 991
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 7
tager is on a distinguished road
I guess you can build a better mousetrap, but the mouse will always be the same.
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
Izzy1414's Avatar
Join Date: Apr 2007
Location: Grants Pass,OR
Posts: 395
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 9
Izzy1414 is on a distinguished road
Both of the incidences cited in the story happened in my neighborhood on roads that I have traveled countless times. While I'm not sure of the exact details of the recent one, I would imagine that the couple turned left prematurely (by a hundred yards or so) onto a USFS service road. It is well marked as not being a thru road. Or they relied on directions from their GPS that routed them over a road that is simply not maintained in the winter. In the highly publicized case in 2006, the Kim family passed several signs warning that the road they were on was not open to winter traffic. Apparently believing the directions of their GPS navigation system more than the signs, they continued on, until they were stuck in the snow, 25 or 30 miles from civilization. In subsequent years, truck dispatchers have sent highway trucks over the same road in the winter, also relying on GPS directions. And it would be unwise and illegal to route commercial trucks over the one lane road any time of the year. So far the only consequence of those debacles have been expensive towing bills when the trucks got stuck ..... Oh, and the fire damage one of the dimwits caused by spinning his wheels til his tires caught fire. Anyway, Jack, you are absolutely correct. People are putting far too much faith in technology (GPS in this case) and not paying enough attention to what their eyes and ears are telling them. The GPS navigation system on a boat or in a car is not a substitute for planning your route. It is a tool that should be used along with other tools and your senses to help you make sure you are where you planned to be.
S/V Boccata d'Aria

I'm not sure what Dickens are, but I think they may be important and I sure as hell don't want them scared out of me.......Izzy

Last edited by Izzy1414; 12-30-2009 at 03:48 AM.
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
Senior Member
Join Date: Dec 2008
Location: Chesapeake
Posts: 472
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
lapworth is on a distinguished road
Mine always takes me down one way streets the wrong way.
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
CaptainForce's Avatar
Senior Member
Join Date: Jan 2006
Location: living aboard since 1972
Posts: 1,712
Thanks: 0
Thanked 12 Times in 12 Posts
Rep Power: 10
CaptainForce will become famous soon enough
The following photo shows an image of my GPS screen and the track of my vessel while at anchor earlier this year.

The small loop at the upper left was my track when entering the area; the scramble around the boat icon was the track laid at anchor and the upper line to the right of the screen was laid at my departure. My anchor alarm was activated by a false reading when, within one second, my position was recorded at the acute angle to the right of the screen and again at a distant point off the screen where the two tracks at the lower left would meet. These anomalies are more likely to occur when a vessel is not underway, but it does happen. On another GPS several years earlier I had a momentary reading that my speed was over 60 knots! These are very brief incorrect data points, but they do occur. The real world always trumps your electronic image! 'take care and joy, aythya crew
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
NICHOLSON58's Avatar
Mark on Camper 58
Join Date: Feb 2009
Location: Grand Rapids Michigan
Posts: 199
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 7
NICHOLSON58 is on a distinguished road
It is well known that there are places where your GPS will show you sailing inland or where it may direct you over a reef. In these cases, the background map source data was bad. Some of the background maps were drawn by British seaman using a sextant over a hundred years ago. Garbage in - garbage out.

I have refused to own a GPS for inland driving. I always prefer maps. If I want the feel of a GPS, I read the map through a soda straw.

I can't imagine being so incompetant with a piece of paper that you would throw all trust to a GPS. I was always suspicious but confirmed when a friend brought on along on a trip to Canada to fish. The first clue was that it didn't recognize rout 550 from Marquette west bound to Big Bay. It said we were driving for 20 miles in forest with no roads. The back roads through Canada were a real hoot.
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
SecondWindNC's Avatar
Senior Member
Join Date: Dec 2008
Location: Washington, NC
Posts: 519
Thanks: 3
Thanked 8 Times in 5 Posts
Rep Power: 7
SecondWindNC is on a distinguished road
This reminds me of Mapquest's directions to my parents' house. Instead of going down the one road that goes all the way from town almost to their front door, it tells you to turn off about a mile before you get there, then routes you through a neighborhood, down a "road" that doesn't exist (there's a trail through the woods there, but it's gated), and then loops back out through another side road to get back on track. Ta da!
Carolina Wind Yachting Center, Washington, NC
Charters * Brokerage * Pacific Seacraft * Zodiac

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

Who is staring at the sea is already sailing a little.
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
flyingwelshman's Avatar
Senior Member
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 1,775
Thanks: 20
Thanked 27 Times in 20 Posts
Rep Power: 8
flyingwelshman will become famous soon enough
I got a new Garmin chart plotter for my big trip last year.

I found the charts to be very accurate and made it home without incident.

Except: while going through some meandering channels behind Shawanaga Island, heading to Pointe Au Baril, I was conscientiously watching the screen on my plotter. There was a convenient mauve line heading off my bow, showing me the direction I was to travel. I made sure that I stayed on that line as the GPS knew which way I needed to go.

My wife piped up and asked where the channel was, as we were heading for some rocks and a small island.

Without looking away from the screen I said we were on course and there should be no island in front of us.

My wife insisted that there was indeed a non-watery obstruction in our path.

Why can't she just trust the technology?

I rolled my eyes and looked up - just to appease her of course, as I knew that I would see nothing but open water ahead: my GPS told me so!

Anyway, sure enough we were heading towards some keel-rending rocks and what looked exactly like an island.

I couldn't see any markers where I expected them to be - where my trusty GPS indicated they should be.

I looked off to starboard and saw something distinctly marker-like, about 100 yards away. 'Why the hell did they move the markers without updating the charts?'

I swung over, avoiding the rocks, and got back onto the channel.

I looked at my GPS and saw that the mauve line was still pointing off my bow in roughly the same direction as the channel.

It then dawned on me: the line was indicating the bearing to my next waypoint - it wasn't making accommodations for land etc. Had I followed the machine blindly our trip would have been cut very short (as would my keel!)

Lessons learned: RTFM; use the technology to assist, but rely on biology i.e. eyes, ears etc.; listen to the admiral.

Just as a footnote, upon arriving home after a two-week cruise around Georgian Bay I found a lovely letter from Garmin. The gist of the letter was that there was a recall of all of their electronic charts as they were off by a few feet. (when I contacted them Garmin informed me that my charts weren't affected by the recall)
1989 Hunter 30'
Southern Georgian Bay

The sea, once it casts its spell, holds one in its net of wonder forever. - Jacques Yves Cousteau
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
Great Lakes Sailor
Join Date: Jul 2001
Location: Saginaw, MI
Posts: 184
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
padean is on a distinguished road
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....
CS 34
Saginaw Bay, Michigan
"The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails." - William Arthur Ward
Reply With Quote Quick reply to this message Share with Facebook
Old 12-30-2009
Faster's Avatar
Just another Moderator
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 16,295
Thanks: 100
Thanked 301 Times in 291 Posts
Rep Power: 10
Faster has a spectacular aura about Faster has a spectacular aura about Faster has a spectacular aura about
Sailing Mexico's Gold coast last winter, the Raymarine plotter showed us a mile or more inland each time we anchored for the night. They've simply digitized the official Mexican charts.. and they are off by quite a bit.

Sure wouldn't consider making a landfall in the dark based solely on the plotter information....

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Reply With Quote Quick reply to this message Share with Facebook

Quick Reply

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

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 01:37 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2015, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) LLC 2000-2012

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