Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 26-08-2015, 06:34   #16
Registered User
 
Jon Hacking's Avatar

Join Date: Sep 2010
Location: Currently cruising Southern Indonesia, heading for peninsular Malaysia
Boat: Wauquiez 45' (now 48') catamaran
Posts: 523
Send a message via Skype™ to Jon Hacking
Re: GPS accuracy

Oh, yes, when you zoom OpenCPN way in, it produces a yellow shadow around your track. That's probably what you're seeing. Hadn't realized you were zoomed in that far...
__________________

__________________
-- Jon Hacking s/v Ocelot
Jon Hacking is offline   Reply With Quote
Old 26-08-2015, 06:47   #17
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
Re: GPS accuracy

(Edit, saw BCN was way ahead of me... ) Try turning off highlight tracks in the settings under the ships tab.

Sent from my HTC_0PCV2 using Cruisers Sailing Forum mobile app
__________________

__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 26-08-2015, 07:02   #18
Registered User
 
phiggins's Avatar

Join Date: Nov 2004
Location: Toronto, Canada
Posts: 1,288
Send a message via Skype™ to phiggins
Re: GPS accuracy

Found a program that comes with the GPS that gives info about it. I used it to turn on WAAS. Will do another run to see how it looks. The circle is the same size. The circle does not appear with tracking disabled.
Attached Thumbnails
Click image for larger version

Name:	GPSInfo.jpg
Views:	84
Size:	117.7 KB
ID:	107965  
__________________
Paul,
" One moment you are running along, the next you are no more." Dean Spanley
phiggins is offline   Reply With Quote
Old 26-08-2015, 07:43   #19
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,387
Re: GPS accuracy

WADR, who cares?

If anyone actually believes that GPS accuracy to 3 meters is important, then one must consider re-learning basic navigation 101.

GPS is a VERY, VERY good guide. Emphasis on GUIDE.

I recommend going back to the suggestion on page one and re-reading Calder's How to Read a Chart book or any other GPS guide on accuracy expectations.
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 26-08-2015, 08:23   #20
Registered User
 
phiggins's Avatar

Join Date: Nov 2004
Location: Toronto, Canada
Posts: 1,288
Send a message via Skype™ to phiggins
Re: GPS accuracy

Yes I guess its the circle around the track. If I turn off track highlighting it disappears. This what it looks like now after a few hours with WAAS on and also I changed the OpenCPN Tracking Precision from low to high so it shows most of the track points.

Well Stu I think a lot of sailors would like to know how accurate their instruments are, but as you say it still should be just a guide.
Attached Thumbnails
Click image for larger version

Name:	2015-08-26_10-15-57.jpg
Views:	90
Size:	327.5 KB
ID:	107971  
__________________
Paul,
" One moment you are running along, the next you are no more." Dean Spanley
phiggins is offline   Reply With Quote
Old 26-08-2015, 08:40   #21
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,387
Re: GPS accuracy

Quote:
Originally Posted by phiggins View Post

Well Stu I think a lot of sailors would like to know how accurate their instruments are, but as you say it still should be just a guide.
Paul,

When I first got my old Magellan Blazer 10 or 12 GPS, no charts, I watched it change the lat/lon every few seconds.

When I got my Garmin GPSMap 76 Cx maybe ten years ago, I watched my "location" jump around when I was in my slip. Gee, it still does! I did exactly what you're doing, by zooming way into "overzoom" on the chart.

What it taught me was never to use the GPS to get back to my slip in a complete whiteout.

They are just NOT that accurate, nor were they ever intended to be.

If you read a tad of history, for example, the old Loran C systems were actually much better at repeat-ability to get BACK to the same point than are old &/or more modern WAAS enabled GPSs.

Too many people think that, because of electronics, precision is enhanced. Nothing could be further from the truth for many reasons, reasons that folks have written entire books about.

That''s all I'm trying to say and it is the basics for navigation of ANY sort.

Also covered in the manual for your own GPS whatever it may be.

Continued Good Luck.
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 26-08-2015, 08:40   #22
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
Re: GPS accuracy

The gps skips the beat once and the two circles overlap giving an illusion of an ovalish shape.

b.
__________________
barnakiel is offline   Reply With Quote
Old 26-08-2015, 09:52   #23
Registered User
 
phiggins's Avatar

Join Date: Nov 2004
Location: Toronto, Canada
Posts: 1,288
Send a message via Skype™ to phiggins
Re: GPS accuracy

Yeah who really needs a GPS, be like Captain Ron...

Just kidding Stu.
Attached Thumbnails
Click image for larger version

Name:	Capn_Ron.jpg
Views:	82
Size:	114.5 KB
ID:	107974  
__________________
Paul,
" One moment you are running along, the next you are no more." Dean Spanley
phiggins is offline   Reply With Quote
Old 26-08-2015, 10:46   #24
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: GPS accuracy

doesn't answer your original question but per monitoring your gps, Try "Visual GPS". My favourite. Has lots of info.

VisualGPS, LLC

you want VisualGPSView
http://visualgps.net/VisualGPSView/default.htm
or VisualGPS
http://visualgps.net/VisualGPS/default.htm
which is the one I am using for a long while
__________________
HappySeagull is offline   Reply With Quote
Old 26-08-2015, 10:52   #25
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,387
Re: GPS accuracy

Quote:
Originally Posted by phiggins View Post
Yeah who really needs a GPS, be like Captain Ron...

Just kidding Stu.
Ah, my favorite! Thanks for remembering, Kitty!
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 26-08-2015, 11:51   #26
Registered User
 
HappySeagull's Avatar

Join Date: Dec 2010
Location: B.C.,Canada
Boat: 29'
Posts: 2,395
Re: GPS accuracy

anyways, you can turn off "Tracking Highlight" in the toolbox and then the "issue" goes away. (If I don't understand it- I look for which wires to cut.Saves Brain Pain
__________________
HappySeagull is offline   Reply With Quote
Old 26-08-2015, 16:46   #27
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: GPS accuracy

Quote:
Originally Posted by Stu Jackson View Post
Too many people think that, because of electronics, precision is enhanced.
It is enhanced. Try taking 10 sextant shots or 10 DR's and see what your precision is.

The problem is that people confuse accuracy with precision.

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 26-08-2015, 20:29   #28
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,023
Re: GPS accuracy

What method of determining speed and position has greater accuracy than GPS?
__________________
transmitterdan is offline   Reply With Quote
Old 26-08-2015, 21:09   #29
Registered User
 
Alan Mighty's Avatar

Join Date: Mar 2014
Location: Scarborough Marina, Moreton Bay
Posts: 662
Re: GPS accuracy

Quote:
Originally Posted by transmitterdan View Post
What method of determining speed and position has greater accuracy than GPS?
For starters:

1. GNSS, or Global Navigation Satellite System, using several sat-nav systems such as the US GPS signals, the Russian Glonass signals, China's BeiDou signal, Japan's QZSS signal, etc etc.

2. GNSS coupled with ground-referenced signals. For example, Yanmar has tested in Australia (and Japan, Taiwan, and the Philippines) its agricultural machinery using Japan's QZSS signals and a local ground-referenced signal. Yanmar reported that its agricultural machinery (tilling soil etc) had horizontal in-accuracy of few centimetres.


3. Land surveying equipment has for several years now used GNSS receivers, some (but not all) with ground-referenced signal reception, with much lower horizontal inaccuracy. Of course that gear is much more expensive than the gear available to recreational sailors. Next time you see a surveyor team, go chat and ask them for a Captain Cook at their gear.

Al
__________________
“Only a fool learns from his own mistakes. The wise man learns from the mistakes of others.” - Otto von Bismarck
Alan Mighty is offline   Reply With Quote
Old 26-08-2015, 21:10   #30
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,387
Re: GPS accuracy

Quote:
Originally Posted by colemj View Post
The problem is that people confuse accuracy with precision.

Mark
Well put, thanks, that's where I was going with the thought.
__________________

__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Reply

Tags
gps

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Chart Accuracy and Detail Comparison r.fairman OpenCPN 15 20-01-2012 12:39
Accuracy of Passage Weather ? Sabbatical II Seamanship & Boat Handling 7 11-01-2012 16:30
iPad vs Garmin - Accuracy ? Username33 Marine Electronics 3 13-08-2011 19:32
Acceptable Accuracy in Celestial Navigation sneuman Navigation 43 02-02-2011 19:45
Astronav. Instrument accuracy and other meanderings. skookum Navigation 13 15-03-2009 11:03



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:37.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.