NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: GPS time for celestial
From: Robert Goley
Date: 1997 May 23, 10:59 EDT
From: Robert Goley
Date: 1997 May 23, 10:59 EDT
I checked the 1995 edition of NIMA's Pub 9, aka Bowditch. Its
references to time, in Chapter 18, are essentially the same as
those in the 1984 edition, Vol. 1.
The 1996 edition of Pub 117, Radio Navigational Aids, has similar
information. Neither publication has much to say about "GPS
time" in their chapters on time.
However, they both have chapters on satellite navigation, Chapter
11 in Bowditch and Chapter 6 in Pub 117. Bowditch uses terms
such as "GPS system time", "clock data", "clock dither", and
"receiver clock bias". Quite frankly I have only a rough
understanding of what these terms mean. I have not and will not
have time to read the chapter in depth. But the following
sentence caught my eye and seems germane: "The navigation
message ... contains coefficients for ionospheric delay models
used by C/A receiver and coefficients used to calculate Universal
Coordinated Time (UTC)." From this I'm assuming (!!!!) that "GPS
time" is UTC.
Lt. Bob Goley, AP, Rockville (Md.) PS, D5
Nautical Cartographer
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