Re: Emergency Braking Was: Re: Beresfield Accident Findings

[pierson@gone.enet.dec.com (dave pierson)]

Full accuracy GPS _IS_ Secret.  The data are there in the bit stream,
encrypted to prevent unauthorized use.  The added cost of decryption is
minimal.  (MY view is that the encryption is reeasonable.  The job of the
providers of the GPS system is NOT to provide precision targetting and
nav data for any government or terrorist with a few $1000.  That other users
COULD use the enhanced accuracy is not real relevant.)

There is 'differential' GPS, which can dedither the signal over a local area,
independent of the crypto, to accuracy of 'inches'.  There are other techniques,
i believe, to accomplish similar.  My understanding (article in RGI) was that
the PTS experiment in the US Northwest used GPS, accurized by axle rev counters
& beacons.

thanks
dave pierson                        |the facts, as accurately as i can manage,
Digital Equipment Corporation       |the opinions, my own.
334 South St                        |
Shrewsbury, Mass USA                 pierson@gone.enet.dec.com
"He has read everything, and, to his credit, written nothing."  A J Raffles
"....the net of a million lies...."	Anon