NavList:

I have a friend in Israel whom I am helping to learn to use his sextant.  He is able to get down to the beach and take sights using the natural ocean horizon where his height-of-eye is 7 feet.  He has had several sights where the difference between his known location (as established by a Garmin GPS watch and confirmed by Google Earth) and his line of position is 2.5 nm. 

He has gotten some oddly inaccurate sights at times, so he has purchased Frank's Anti-Spoof app.  When he compares his work to the app, he gets terrific agreement.

However, he recently took two sights of Arcturus that were 3 minutes apart, and the difference between his known location and the LOPs was 36 nm and 40 nm.

We have confirmed the adjustment of his sextant mirrors, and the instrument has sustained no damage between one of his 2.5 nm sights and this pair of 36 and 40 nm sights.

I find it hard to believe that he could make an error of over 1/2° in his sextant height.  However, we know for sure that the Russians have been spoofing GPS from an airbase in Syria.

My question is this:  if the Russians are skewing the GPS readings on his Garmin device around, would that also lead the Garmin device to be displaying the wrong time?

Bob

He has used