Selective Availability

[BullZie]

I was talking to my folks a few days ago and they heard on CBC that there is a risk of Selective Availability being turned on again due to the current war. This would making caching next to impossible as it was SA being turned off that prompted the whole concept of this game. I was wondering if anyone else had heard rumours of this.

 

Bullzie

[BullZie]

Ok, after a quick search I found that this is already a topic of conversation. Anyone have any bets to place an if this could become a problem?

 

http://www.igeb.gov/sa.shtml

 

Bullzie

[+Couparangus]

It is my understanding that SA may be turned on for certain geographic areas but not others. I can see merit for having it on in the gulf region right now, but not in North America.

[+PDOP's]

Copied this from the GPS newsgroup (sorry about the format)

 

The following message from the Office of the Executive Secretariat, Interagency GPS Executive Board (IGEB), confirms the current and continuing

policy on availability of GPS to civil users worldwide, except for possibly in the area of the Iraq conflict.

 

The complete policy statement is available at the IGEB website:

http://www.igeb.gov/sa.shtml

 

Additionally, the policy statement and additional information on GPS status are available at the U.S. Coast Guard (USCG) Navigation Center website for "GPS General Information"

<http://www.navcen.uscg.gov/gps/default.htm>

 

Feel free to distribute this notice to anyone else who may be concerned about continuing availability of GPS signals for the civil user community.

 

Should anyone experience problems in receiving signals from any of the GPS satellites, please contact the USCG Navigation Center

<http://www.navcen.uscg.gov>.

 

Information on GPS Service Interruptions

are found at: <http://www.navcen.uscg.gov/gps/gpsnotices/default.htm>

 

To report a GPS problem, go to:

<http://www.navcen.uscg.gov/gps/gpsuserinput.htm>.

"GPS Operational Advisory" is found at: <http://www.navcen.uscg.gov/ftp/gps/status.txt>.

 

The USCG Navigation Information Service watchstander is available 24 hours a day for handling user inquiries on GPS at: 703-313-5900, Fax: 703-313-5920, and <nisws@navcen.uscg.mil>.

 

PDOP's GPS Pages

[BullZie]

So I would read from that that they are able to selectively control SA then? Such as leaving it off in North American but turning it on over Iraq?

[+PDOP's]

quote:

---

Originally posted by Bullzie:

So I would read from that that they are able to selectively control SA then? Such as leaving it off in North American but turning it on over Iraq?

---

 

I think so. Look at this thread for more.

 

PDOP's GPS Pages

[+Bzzliteyr]

Well, I am going to assume that they have done nothing yet, and the ground war is already long underway.. the reason I say this is that I was getting +-3 meters accuracy yesterday on my Garmin Legend, that is rare for me on a regular day, let alone a war day!!

 

Bzz

[Peregrine007]

Apparantly, even when SA was active, your GPSr would not include the degree of error due to SA in its accuracy or "EPE" reading. The reasoning is that the GPSr has no way of knowing that SA is active, so it could still say that its accuracy was 3m even though SA would take its actual accuracy to over 100m. At least, that's what I understand... there's more on this topic in the book "GPS Made Easy" by Lawrence Letham.

 

[This message was edited by Peregrine007 on April 02, 2003 at 02:28 PM.]

[+Bzzliteyr]

So, theoretically I would have to go to a known waypoint on my GPS and stand near it and see if it gave me the same grid? That would be the best way to test if SA would be active or not, wouldn't it?

Bzz

[Peregrine007]

Yes, that would be one way of doing it... although I think even just standing in one place, the GPSr would tell you that you were moving all over the place. This is probably all irrellevant anyways, as I would highly doubt that SA will ever be reinstated anyways. Too many non-governmental people and organizations use GPS now that there would be huge repercussions if their accuracy were suddenly detroyed.