[time-nuts] GPS Positions

[Brian Kirby]

Today I had to power down my equipment and reconfigure my power feeds 
and UPS system to the timing station.

When I brought everything back up and let it warm up, I started 
synchronizing my clocks to UTC via a HP Z3801A GPSDO.  Somehow, one of 
my GPS receivers, a Motorola Oncore VP, got a trashed position and it 
was showing time out by 140 milliseconds.  I brought up TAC32 and it 
showed the position was not where I surveyed it.  I did not think to 
record the bad position and the timing error.  But It gave me an idea 
and the un-scientific results are as follows.

I set the position off on the Oncore VP by -1 minute of latitude.  The 
time error was +1.4 uS.
-3 minutes was +4.2 uS.
-5 minutes was +6.8 uS.
-10 minutes was +13.3 uS
-30 minutes was +45.0 uS.

Then I put the unit back to its referenced position and played with 
altitude. 
I really could not see any big changes until I raised the position by 
500 meters, and it read +1.0 uS.
At +1000 meters, it was +1.7 uS.
At +5000 meters is was +9.7 uS.

Brian KD4FM