I thought some of you might find the following article of interest,
if only to make your education concerning GPS more complete and on
the off chance that you might want to venture above 80 North or South.

http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=72174

A few excerpts.
Several unique phenomena affect GPS performance at high latitude,
where the satellite constellation changes dramatically due to the
inclination of the GPS satellite orbits. No satellites pass directly
overhead as one approaches the North Pole. Instead, all satellites
appear closer to the horizon, and at very high latitudes (greater
than 80 degrees) satellite visibility increases to 12 or more at
low-elevation angles. This produces a reduced geometry as well as a
high-potential multipath environment.

The northernmost settlement in Canada and in the world, Alert lies
450 nautical miles from the North Pole. Figure 1 shows elevation
angles for latitude 82 degrees north. As many as 15 or 16 satellites
may be visible during the day, but satellite elevations rarely rise
above 45 degrees. The resulting position dilution of precision (PDOP)
varies from a very respectable 1.5 to 2.0 to as high as 5.5 with
numerous spikes for short periods of time.

Regards,
Mike

Capt. Mike Maurice
Tualatin(Portland), Oregon

Last week, MSNBC had a brief article about the blast off of a rocket
containing the first of a whole new system of GPS satellites.  The new
system is supposed to be "bigger, better, more accurate, blah blah blah
(insert media filler here)...."  Very few details were given.  It sounds
great.  However, there was mention of a second frequency.  Does this
mean we will need new equipment?

Any insider info on TWL?

Eric Thoman
Abyssinia

There is a website named www.gpsworld.com . The following may be the "2nd"
channel. As far as I am aware, the "3rd" channel is a military positioning
system, although other sources suggest they have an independent system.

"Time Reference Frame - The Galileo System Time (GST) shall be a continuous
coordinate time scale steered towards the International Atomic Time (TAI)
with an offset of less then 33 nanoseconds. The GST limits, expressed as a
time offset relative to TAI, should be 50 nanoseconds for 95 percent of the
time over any yearly time interval. The difference between GST and TAI and
between GST and UTC(Pred) shall be broadcast to the users via the
signal-in-space of each Galileo service.
The Galileo ground segment will monitor the offset of the GST with respect
to the GPS system time and eventually broadcast the offset to users. The
offset could also be estimated in the user receiver by "spending" just one
satellite observation. The accuracy of the receiver solution would probably
be higher than the one (eventually) transmitted. Thus, broadcasting might
not be necessary for the general navigation user.

Ron Rogers

----- Original Message -----
From: "Kim Boyce and Eric Thoman" kimeric@seanet.com

| Last week, MSNBC had a brief article about the blast off of a rocket
| containing the first of a whole new system of GPS satellites.  The new
| system is supposed to be "bigger, better, more accurate, blah blah blah
| (insert media filler here)...."  Very few details were given.  It sounds
| great.  However, there was mention of a second frequency.  Does this
| mean we will need new equipment?
|
| Any insider info on TWL?

Further reading:

" The first IIR-M (replacement, modernized) GPS satellite has gone aloft.
Carrying the capacity to implement the new military signals (M-code on L1M
and L2M) and a second civil signal (L2C), the two-ton, $75 million GPS
IIR-M1 spacecraft rose successfully into a temporary orbit at 3:37 a.m. on
September 26."

[demime 1.01d removed an attachment of type image/gif which had a name of clear_dot.gif]

Hi list,

I recently had to replace the heat exchanger on one of my Perkins
6.354 engines.  The old one was cracked.  The dompany that supplied
the new heat exchanger recommended that I drain and replace all of
the coolant in the engine.  Here is my question:  Where is the engine
block drain plug on the Perkins 6.354 engine.  I've looked all over
the engine and can't find anything that looks like a coolant drain
plug.  I drained the tank and the heat exchanger before I removed
them, but now I need to also drain the engine block.

Thanks in advance

Dean Smith
Desiderata
Californian 38 Tri-cabin
Everett, WA

Thank you to all of the folks who sent me the "light reading" on GPS
signals.  The conclusions that I have gleamed are:

1. There will ultimately be three GPS signals to choose from for
   consumer purposes, L1, L2 and L5.  Each has a different frequency and
   attributes.  We are currently using L1 and it may eventually be tweaked
   to make it better.  It will not go away.  You will not receive L2 and L5
   with your L1 receiver.

2. Better consumer products will likely use multiple signals (for
   example L1 and L2) for accuracy and redundancy.

3. The rockets and satellites have fancy numeric names (such as 2R-M1)
   that the authors who write about this stuff like to throw around but the
   signals that they send is what really matters.  It is confusing because
   each satellite puts out multiple signals in order to operate the
   different systems, including military.

As navigators, how could you resist upgrading to the new products when
they come out?

Please feel free to add your own conclusions to the list.

Eric Thoman
Abyssinia