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http://www.spacedaily.com/2003/03031815 ... a5u.htmlIs this true?

There is a chance that the US DoD turn the GPS Selective Availability (SA) back on... but I really don't think so.On May 1st 2000, President Bill Clinton made a statement regarding the US decision to stop degrading the GPS accuracy and make a PORTION (L1 band) of the GPS signal available to the civilians... for ever. L2 band is still for a military use only (better accuracy)...If they decide to turn SA back on... they are obliged to issue a NANU (Notice Advisory to Navstar User)... because it is a BIG security issue for ships and airplanes using GPS. But there will be no danger for those using DGPS (Differential GPS).So, I don't think the War will affect navigation systems... but we'll see!Ref : - Selective Availability : http://www.navcen.uscg.gov/gps/selectiv ... ility.htm- NANUs : http://www.navcen.uscg.gov/ADO/GpsActiveNanu.asp

quote:So, I don't think the War will affect navigation systems... but we'll see!It is highly unlikely they will turn SA back on. GLONASS, the Russian GPS system, will provide an easy way around SA. So I don't think they will risk losing out to their system.

Think of "Selective Availability" as intentional error. GPS use to have it in the signal to make gps trackers less accurate, giving only the very accurate readings (down to a few centimeters), to the military. Among other things, they were scared that the system would be used to guide terrorist weapons...and bla bla bla...if it was set too accurate. Use to make gps only accurate within 100m or so. Now it is accurate with-in several feet, with SA turned off. Still not as accurate as the military has, but its accurate enough.

In fact, they're using DGPS (Differential GPS) combining the GPS signal to a beacon signal broadcasting the GPS corrections for every visible satellites from a Reference Station (RS) placed at a surveyed position. The RS knowing precisely where he is in longitude, latitude and altitude can then broadcast corrections. So, the DGPS is accurate in terms of centimeters (from 0 to 30 cm).And still in development... there is another system combining the GPS, DGPS and Loran-C... again to be more accurate! But how can you be more accurate than 0 to 30 cm provided by the DGPS?!?! I think that some developers are kinda obsessive... eheh

Yeh, I think 30 cm is probably sufficient when you're using 22,000 lb bunker busters anyway!

Will it help me find my keys?