See we told ya

[byron]

<font color=blue>See! Duncan and I told you there would be no degradation of the GPS with the onset of the Iraqi war.
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[Steve_D]

I left my handheld outside for half an hour or so this evening and it so far has not shown any of the characteristic 'drift' that you used to see with the selective availability switched on, but I guess there's still time.

This may negate some of my own argument but there is an interesting article regarding the use of GPS in aviation at

http:// [url]www.caa.co.uk/docs/224/srg_gad_ssl25.pdf [/url]

a lot of the issues won't effect a boat because

a) there is going to be less interference around than on land
b) I would suggest that the poo hits the fan a bit slower on a boat than in a plane/glider.

but interesting reading non the less

Regards

Steve D

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[BrendanS]

Steve

I think you may be missing the point here. Selective Availability was usually switched OFF when wars kicked off, so that the GPS system provided the maximum accuracy. It was noticeable how much more accurate the system was during the last Gulf War.

However, it was decided some years ago to turn off the Selective Availability option some years ago, since when the GPS system has provided accuracy down to several metres. It would be counter productive to turn on SA during a war.

The link you provided didn't work as you had a space in between http:// and www

try this <A target="_blank" HREF=http://www.caa.co.uk/docs/224/srg_gad_ssl25.pdf>http://www.caa.co.uk/docs/224/srg_gad_ssl25.pdf</A>

Interesting site, but it's common sense not to rely totally upon GPS when navigating boat or plane, and I've done both. Look around the forums here and you'll see similar messages not to rely upon GPS, but SA and war are not the issues. The real issue is dependance upon electronic nav aids, rather than ability to combine using nav aids and traditional skills when the electronics go wrong

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[Steve_D]

I fully understood the point that was being made. But it was assumed that last time around the SA was switched off because the allied forces were reduced to using commercial equipment due to there not being enough milspec gear available.

I understand that this is not the case this time around, however the thread that appears elsewhere with the link to the navigation society explains the technology better and would indicate that the SA was switched off, in part, to allow the milspec equipment available at that time to function correctly. From that article I understand that this latter point is not now the case and they COULD switch off the SA without affecting the milspec sets which are now able to function using the longer 'key'. But that this is now largley redundant due to the development of 'theatre' methods of controlling the GPS system (this is also one of the points raised in the CAA article regarding flying around army exercises).

The Navigation society article indicates that as result of this latter development it is no longer neccessary to use SA and the US government has stated that it will not be used in the future.

I found both of the articles very interesting and informative and would advocate care when using any form of artificial navigation aid, including the humble compass, which, I would suggest, is more susceptable to interference than GPS. I'm sure that i'm not the only one to have placed a steel flask, phone, torch, etc too close to a compass.

Regards

Steve D

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