Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 07-02-2016, 16:00   #46
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,713
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by OldFrog75 View Post
I have never seen seconds taken to 3 decimal points on a gps device whereas minutes are always taken to 3 decimal points - at least that's the way it is on my Garmin.

The OP was questioning which is better for navigation seconds or minutes. It devolved into a debate about which is more accurate. Perhaps I misunderstood but I assumed it was in the context of what information would be readily available on someone's gps device (handheld or otherwise) or a paper chart.
The information most readily available on the GPS is whichever the user has configured the GPS for.

The information most readily available on a paper chart is decimal minutes.
__________________

__________________
StuM is offline   Reply With Quote
Old 07-02-2016, 16:14   #47
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,713
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by estarzinger View Post
So, true cautionary tale about mis-communication with all these different formats. . . . . In the Aegean incident (boat lost in Mexico with all hands), SPOT (or more accurately GEOS, which is SPOT's emergency signal subcontractor), gave out a position of the SOS, which the family, race coordinator uscg interpreted as d MM.MMM. They also gave out a time for the SOS message, which was interpreted as local time. They wasted a bunch of time looking at that location and time/drift rate. And then it was discovered that the stated location was in D.ddddd and the time was in UTC. And it became very obvious where the boat was (ashore on a rocky island).
Interesting take on it, but that's not what I understand happened at all.

According to this article, there was no position data:

http://www.langleysquadron.com/uploa...nd_devices.pdf

And according to this one:

Maker of GPS device sued in yacht race crash that left 4 sailors dead - latimes

"Court documents state that about 1:30 a.m. April 28, 2012, the Aegean somehow became disabled. When the SOS emergency function on the Spot Satellite GPS Messenger was activated, emergency responders were never notified, the complaint alleges."
__________________

__________________
StuM is offline   Reply With Quote
Old 07-02-2016, 20:36   #48
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by StuM View Post
The information most readily available on the GPS is whichever the user has configured the GPS for.
As well, make sure your GPS (not chartplotter) is configured for the same horizontal datum which your chart(s) use(s).
__________________
ISPA Yachtmaster Ocean 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)
jackdale is offline   Reply With Quote
Old 07-02-2016, 20:41   #49
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Different numbers for "Seconds" in Lats and longs?

Should be required reading. SPOT is not an replacement for either PLBs or EPRIRBs.
__________________
ISPA Yachtmaster Ocean 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)
jackdale is offline   Reply With Quote
Old 07-02-2016, 21:24   #50
CF Adviser

Cruisers Forum Supporter

Join Date: Aug 2009
Boat: Custom Van De Stadt 47 Samoa
Posts: 3,744
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by StuM View Post
Interesting take on it, but that's not what I understand happened at all."
Stu, I was on the accident investigating team. I have all the raw data and inputs.

There was a sos message sent. With a time stamp, but no location data. However the spot had been set to auto position reporting (I think every 10 minutes), so there was also a track position (with valid location data) from only a short time before the sos message (I think 4 minutes).

There were further problem(s) with geos internal protocols, which caused all this to be reported hours after it should have been. But those are a bit off topic since the thread is about location formatting.

I have copies of all the spot messages and all the communications with the family, Rc and uscg and all of gros's internal protocols . . . As I was the team member specifically designated to dig into the spot aspect of the incident.
__________________
estarzinger is offline   Reply With Quote
Old 12-02-2016, 10:26   #51
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by jackdale View Post
I have asked a couple of squash friends who are geomatics engineers about that. I will post their response(s).

The "standard" used in the navigation programs that I teach is degrees, minutes, 10ths of minutes (AKA cables).
As promised.

Quote:
I wouldn’t say that there is necessarily a standard, Jack. In the world of engineers, most would likely prefer decimal degrees which is what you have indicated below. The main reason for this is it is easy for them to understand and use in calculations.

Surveyors often use a combination of Degrees, min, seconds and Decimal degrees. We always indicate bearings and azimuths as Deg,min, sec. latitude and longitudes are often provided in both dms and dd.

The statement below is true – it’s the preferred method when it comes to the ISO standard but we use whatever our end user requires.
__________________
ISPA Yachtmaster Ocean 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)
jackdale is offline   Reply With Quote
Old 12-02-2016, 11:50   #52
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,042
Re: Different numbers for "Seconds" in Lats and longs?

You could say the ISO standard is just that: Words on paper. There are ISO9000 standards for manufacturing and businesses, and when properly implemented they can be a great thing, but sailors tend to follow TRADITION unless someone has a Real Damned Good Reason for change. And since we all (ahem) already know, expect, and use the old DDD.MM.SS format...even if the ISO standard gives better precision, we generally can't use it. No one wants or needs to know their vessel position with two centimeters, really, do they? And if it takes a few less data bits to record or transmit, a little less bandwidth...we're already working with what we've got, aren't we?


So, "engineering" formats, for ships? Maybe first they could promote an ISO standard for a bottom paint that worked.(G)
__________________
hellosailor is offline   Reply With Quote
Old 12-02-2016, 12:06   #53
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,387
Re: Different numbers for "Seconds" in Lats and longs?

Interesting banter.

OK, I'll giver it a go.

It simply doesn't matter.

Why?

Which are "better?":

miles, kilometers, nautical miles, feet, inches, fathoms, cables...

They are all a measure of distance.

Analogous to this.

And meaningless differences in the real world, except for misusing or misinterpreting them.
__________________
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 12-02-2016, 12:53   #54
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,042
Re: Different numbers for "Seconds" in Lats and longs?

"10ths of minutes (AKA cables). " So the length of a Canadian Cable varies with whether it is being used for latitude or longitude, and at what point on the sea or earth?


Minutes, after all, unless being used as arc radial measurements, are of varying lengths, significantly varying lengths, at the equator and near the poles.


I find fathoms useful, in that the "average" man standing with arms fully outspread, will have about a six foot spread, so one "armspread" of line will often be close to a fathom.
__________________
hellosailor is offline   Reply With Quote
Old 12-02-2016, 13:16   #55
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by hellosailor View Post
"10ths of minutes (AKA cables). " So the length of a Canadian Cable varies with whether it is being used for latitude or longitude, and at what point on the sea or earth?


Minutes, after all, unless being used as arc radial measurements, are of varying lengths, significantly varying lengths, at the equator and near the poles.


I find fathoms useful, in that the "average" man standing with arms fully outspread, will have about a six foot spread, so one "armspread" of line will often be close to a fathom.
A cable is one tenth of a nautical mile, which is one minute of latitude on a chart.
__________________
ISPA Yachtmaster Ocean 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)
jackdale is offline   Reply With Quote
Old 12-02-2016, 13:25   #56
Senior Cruiser
 
jackdale's Avatar

Cruisers Forum Supporter

Join Date: Mar 2008
Location: Calgary, AB, Canada
Posts: 5,048
Images: 1
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by Stu Jackson View Post
Interesting banter.

OK, I'll giver it a go.

It simply doesn't matter.

Why?

Which are "better?":

miles, kilometers, nautical miles, feet, inches, fathoms, cables...

They are all a measure of distance.

Analogous to this.

And meaningless differences in the real world, except for misusing or misinterpreting them.

Rather the question is what is "conventional."

As we all know.

In the marine world, distances are measured in nautical miles, speeds (boat, wind, current) in knots.

Most of the world using meters, rather than fathoms and feet, for depths. Which why we have to read title blocks.
__________________
ISPA Yachtmaster Ocean 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)
jackdale is offline   Reply With Quote
Old 12-02-2016, 13:35   #57
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,387
Re: Different numbers for "Seconds" in Lats and longs?

Quote:
Originally Posted by jackdale View Post
Which why we have to read title blocks.
So very important, so little understood. Great point.
__________________

__________________
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

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
This viking longs to cruise. ulfurk Meets & Greets 2 08-01-2014 12:24
can I mix different rudder angle indicator and different autopilots awab Marine Electronics 11 24-04-2013 15:25
Racer Who Longs to Be a Cruiser kvidal Meets & Greets 5 26-07-2011 19:40
explosion at the lats and atts site irwinsailor The Library 5 24-02-2005 15:30



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 02:00.


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.