External GPS antenna and WAAS?
 

On Sun, 18 Jan 2004 17:03:57 GMT, (Larry W4CSC) wrote:


On a more serious note, I don't believe the GPS has to have CONSTANT
WAAS data to make it accurate. The drift you get corrected for is
VERY slow moving, so if it had a lock on WAAS data every few minutes
that should be good enough for good correction, shouldn't it? I'd
think the manufacturers would tell the receiver to use the LAST
available data until new data arrives.

It is my understanding that the software in WAAS enabled receivers do
not check constantly - that is my understanding.

Curiously enough, I have a Magellon 315 and 330M and the 315 is a tad
more accurate (will show zero error for instance) than the 330 (I
never get zero error) which is WAAS enabled.

When I first noticed that, I thought that the WAAS receiver would be
more accurate.

Later,

Tom
S. Woodstock, CT
----------
"My rod and my reel - they comfort me."

St. Pete, 12 Lb. Test

External GPS antenna and WAAS?
 

That "error" calculation may not include the accuracy added by WAAS.
And it is a SWAG based on satellite geometry at the moment, and the
two receivers may use different SWAGs.

--
Chuck Tribolet

http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Short Wave Sportfishing" wrote in message ...
On Sun, 18 Jan 2004 17:03:57 GMT, (Larry W4CSC) wrote:


On a more serious note, I don't believe the GPS has to have CONSTANT
WAAS data to make it accurate. The drift you get corrected for is
VERY slow moving, so if it had a lock on WAAS data every few minutes
that should be good enough for good correction, shouldn't it? I'd
think the manufacturers would tell the receiver to use the LAST
available data until new data arrives.

It is my understanding that the software in WAAS enabled receivers do
not check constantly - that is my understanding.

Curiously enough, I have a Magellon 315 and 330M and the 315 is a tad
more accurate (will show zero error for instance) than the 330 (I
never get zero error) which is WAAS enabled.

When I first noticed that, I thought that the WAAS receiver would be
more accurate.

Later,

Tom
S. Woodstock, CT
----------
"My rod and my reel - they comfort me."

St. Pete, 12 Lb. Test

External GPS antenna and WAAS?
 

On Sun, 18 Jan 2004 19:57:09 GMT, Short Wave Sportfishing
wrote:


It is my understanding that the software in WAAS enabled receivers do
not check constantly - that is my understanding.

Curiously enough, I have a Magellon 315 and 330M and the 315 is a tad
more accurate (will show zero error for instance) than the 330 (I
never get zero error) which is WAAS enabled.

When I first noticed that, I thought that the WAAS receiver would be
more accurate.

Aboard Lionheart, leaving the Raymarine Raystar 120 Seatalk WAAS-GPS
and its RL70CRC Plus radar display/chartplotter on for long periods of
time tied to E-dock, I plot the Raystar 120's position centered around
its position on the hard top varying from about 30' off the stern to
near the bow to about halfway across the boats next door to port and
starboard, easily within the 3 meter accuracy circle that's specified.
The boat's in Charleston, SC, so has good WAAS view at about 45
degrees elevation.

It's not quite good enough for ILS approach, but damned close!

Clicking the waypoints on top of a bouy symbol is NOT a good idea....



Larry W4CSC

External GPS antenna and WAAS?
 

On Sun, 18 Jan 2004 14:11:09 -0800, "Chuck Tribolet"
wrote:

That "error" calculation may not include the accuracy added by WAAS.
And it is a SWAG based on satellite geometry at the moment, and the
two receivers may use different SWAGs.

Good point.

Later,

Tom
S. Woodstock, CT
----------
"My rod and my reel - they comfort me."

St. Pete, 12 Lb. Test

External GPS antenna and WAAS?
 

On Mon, 19 Jan 2004 03:21:07 GMT, (Larry W4CSC) wrote:

On Sun, 18 Jan 2004 19:57:09 GMT, Short Wave Sportfishing
wrote:


It is my understanding that the software in WAAS enabled receivers do
not check constantly - that is my understanding.

Curiously enough, I have a Magellon 315 and 330M and the 315 is a tad
more accurate (will show zero error for instance) than the 330 (I
never get zero error) which is WAAS enabled.

When I first noticed that, I thought that the WAAS receiver would be
more accurate.

Aboard Lionheart, leaving the Raymarine Raystar 120 Seatalk WAAS-GPS
and its RL70CRC Plus radar display/chartplotter on for long periods of
time tied to E-dock, I plot the Raystar 120's position centered around
its position on the hard top varying from about 30' off the stern to
near the bow to about halfway across the boats next door to port and
starboard, easily within the 3 meter accuracy circle that's specified.
The boat's in Charleston, SC, so has good WAAS view at about 45
degrees elevation.

It's not quite good enough for ILS approach, but damned close!

Clicking the waypoints on top of a bouy symbol is NOT a good idea....

I could tell you a story, but it would take to much bandwidth. :)

I tried the same thing by comparing the Furno to the Megellon
handhelds by leaving them all on at a dock one day while I was helping
my brother with his boat.

They were all pretty accurate within their specifications.

Later,

Tom
S. Woodstock, CT
----------
"My rod and my reel - they comfort me."

St. Pete, 12 Lb. Test

External GPS antenna and WAAS?
 

On the west coast, the WAAS birds are only about 15 degrees above
the horizon . . .

If the DirecTV test below is accurate, it's 33.4 degrees @ Portland,
still quite blockable in terrain and urban canyons.

External GPS antenna and WAAS?
 

The drift you get corrected for is
VERY slow moving, so if it had a lock on WAAS data every few minutes
that should be good enough for good correction, shouldn't it?

On a good day, yes, but on a bad day in some parts of the globe
ionospheric propagation delay can change rapidly, to the point of
scintillation.

External GPS antenna and WAAS?
 

On 22 Jan 2004 19:39:21 -0800, (Mark) wrote:

The drift you get corrected for is
VERY slow moving, so if it had a lock on WAAS data every few minutes
that should be good enough for good correction, shouldn't it?

On a good day, yes, but on a bad day in some parts of the globe
ionospheric propagation delay can change rapidly, to the point of
scintillation.

WAAS isn't global. The footprint is very defined, like any
geostationary satellite.


Larry W4CSC

Is it just me or did the US and UK just capture 1/3
of the world's sweetest oil supply? What idiot wants to
GIVE IT BACK?!!
Let's do what Europeans have been doing for centuries.
DIVIDE UP THE SPOILS OF OUR CONQUEST! Gas will be
$US0.50/US gallon again, STUPIDS!

External GPS antenna and WAAS?
 

The DirecTV test is wrong because the DirecTV bird is much closer to due south
of the western US than either of the WAAS birds. I dug up the orbital elements
for the WAAS birds and plugged them into a satellite position calculator I had.
It's about 15 degrees.

--
Chuck Tribolet

http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Mark" wrote in message om...
On the west coast, the WAAS birds are only about 15 degrees above
the horizon . . .

If the DirecTV test below is accurate, it's 33.4 degrees @ Portland,
still quite blockable in terrain and urban canyons.

External GPS antenna and WAAS?
 

Here are URLs for calculating how high above the horizon the WAAS birds a

http://www.lyngsat.com/tracker/inmar3f3.shtml
http://www.lyngsat.com/tracker/inmar3f4.shtml


--
Chuck Tribolet

http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Chuck Tribolet" wrote in message ...
The DirecTV test is wrong because the DirecTV bird is much closer to due south
of the western US than either of the WAAS birds. I dug up the orbital elements
for the WAAS birds and plugged them into a satellite position calculator I had.
It's about 15 degrees.

--
Chuck Tribolet

http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Mark" wrote in message om...
On the west coast, the WAAS birds are only about 15 degrees above
the horizon . . .

If the DirecTV test below is accurate, it's 33.4 degrees @ Portland,
still quite blockable in terrain and urban canyons.