Reply
 
Thread Tools Display Modes
 
Old 09-23-2015, 08:34 PM   #1
Member
 
City: Sidney BC
Country: Canada
Join Date: Sep 2014
Posts: 6
Selective availability.

I was informed by an instructor of the Seamanship Course of the Canadian Power Squadron that the US Government re-introduced selective availability in their GPS Signals on or after 911. I have not heard of this before and cannot find a link to any suggestion that it happened. Does anyone know whether this allegation is factual? It was used as one reason why a seaman should never trust a GPS.
__________________
Advertisement

maac16324 is offline   Reply With Quote
Old 09-23-2015, 09:55 PM   #2
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 4,817
Won't speak to whether a seaman can trust it (I do). Just curious what he thinks all the airplanes are using, same system. While the accuracy is exceptional compared to loran, one is still limited by the interface between the map on your plotter and your very accurate position from GPS. The ability to turn the system off or increase a substantial error, exist in the event of a pending missile strike. If it were to have been turned off or accuracy altered as a preparedness test, the accidental deaths associated with it, would have been headline news for weeks.

Ted
__________________

__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 09-23-2015, 10:12 PM   #3
TF Site Team
 
FlyWright's Avatar
 
City: California Delta and SF Bay
Country: Sacramento, CA, USA (boat in Vallejo)
Vessel Name: FlyWright
Vessel Model: Marshall Californian 34 LRC
Join Date: Apr 2008
Posts: 10,180
Not true. SA has been turned off since the Clinton years.

Positioning has been improved in following years with WAAS and LAAS. A google search will explain those terms if you're not familiar.

Aviation systems depend on accuracy and have become more dependent on GPS each year. The 3D positioning accuracy is integral to the use of RNAV approaches and some departure procedures.

Wide areas of GPS signal jamming by the military and industrial testing are commonplace. These are normally made public through Notices to Airmen.
__________________
Al

Custom Google Trawler Forum Search
FlyWright is offline   Reply With Quote
Old 09-23-2015, 10:18 PM   #4
Guru
 
City: Satsuma FL
Country: United States
Vessel Name: No Mo Trawla
Vessel Model: Hurricane SS188
Join Date: Jul 2014
Posts: 1,681
Urban legend.

What I have read is SA was removed from future satellites starting in 2007 or 2008.
Donsan is offline   Reply With Quote
Old 09-24-2015, 07:12 AM   #5
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,530
"Wide areas of GPS signal jamming by the military and industrial testing are commonplace."

And many bars and truck stops as drivers do not want the boss to know their location.
FF is offline   Reply With Quote
Old 09-24-2015, 12:34 PM   #6
Member
 
City: Sidney BC
Country: Canada
Join Date: Sep 2014
Posts: 6
Instructor changed position.

The Canadian Power Squadron instructor changed their position saying that although it was discussed selective availability was never re-introduced on or after 911. I guess that means I don't have to throw my GPS chart plotters overboard.
maac16324 is offline   Reply With Quote
Old 09-24-2015, 01:21 PM   #7
Guru
 
TDunn's Avatar
 
City: Maine Coast
Country: USA
Vessel Name: Tortuga
Vessel Model: Nunes Brothers Raised Deck Cruiser
Join Date: Feb 2015
Posts: 672
I am not worried about it. My new antenna picks up GLONASS satellites too.
TDunn is offline   Reply With Quote
Old 09-26-2015, 12:31 AM   #8
Guru
 
MYTraveler's Avatar
 
City: West Coast
Country: USA
Join Date: Apr 2014
Posts: 852
It would make sense that they retained the capability to quickly turn it on in appropriate circumstances.
MYTraveler is offline   Reply With Quote
Old 10-03-2015, 07:00 PM   #9
Guru
 
High Wire's Avatar
 
City: Cape May, NJ and Englewood, FL
Country: USA
Vessel Name: Irish Lady
Join Date: Dec 2007
Posts: 1,602
If you ever decide to throw your plotters overboard again, PM me and I'll pay the shipping.
__________________
Archie
1984 Monk 36 Hull #46
Englewood, FL and Cape May, NJ
High Wire is online now   Reply With Quote
Old 10-03-2015, 07:10 PM   #10
Guru
 
City: Sydney
Country: Australia
Join Date: Jul 2015
Posts: 1,352
I'm presently within 500mm on my google map on my iPhone that's close enough for me .
gaston is online now   Reply With Quote
Old 10-03-2015, 08:22 PM   #11
Guru
 
Northern Spy's Avatar
 
City: Powell River, BC
Country: Canada
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 2,668
Quote:
Originally Posted by MYTraveler View Post
It would make sense that they retained the capability to quickly turn it on in appropriate circumstances.
The new birds have separate signals for military and civilian. I think the separate band intent is not for turning it off so others can use, but to keep the military signal from bring jammed. GPS III is way behind schedule.

Supposedly the new satellites don't even have SA capability anymore.

I find my GPS gets a quicker fix from the stronger signal strength if the Glossnas satellites.
__________________

Northern Spy is online now   Reply With Quote
Reply

Thread Tools
Display Modes

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





All times are GMT -5. The time now is 08:46 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012