PRN133 ranging now useable for SoL, at non precision approach level

Since PRN133 was set healthy for WAAS corrections, its ranging was
kept at NM (Not Monitored) level, preventing its use for safety of
life applications, however in the last few days, its ranging improved
to UDRE 50 meters, which allows it to contribute for non precision
approaches.

With this improvement now all 3 WAAS satellites have ranging useable
for navigation. The other two WAAS satellites usually work at UDRE 7.5
meters which allows it to contribute even to precision approaches.

In contrast, GPS satellites normally operate at 3 meters UDRE, the
best accuracy WAAS allows any ranging source to achieve.

PRN133 has been performing at UDRE of 50 with some degradation to 150.

This is most useful in South America since PRN133 has the best view of
South America of all GEOs, and with a WAAS compatible receiver capable
of tracking two SBAS GEOs, you would effectively get two extra GPS
satellites.

Marcelo Pacheco

On 2011-10-30 16:44 , macpacheco wrote:
Since PRN133 was set healthy for WAAS corrections, its ranging was
kept at NM (Not Monitored) level, preventing its use for safety of
life applications, however in the last few days, its ranging improved
to UDRE 50 meters, which allows it to contribute for non precision
approaches.

With this improvement now all 3 WAAS satellites have ranging useable
for navigation. The other two WAAS satellites usually work at UDRE 7.5
meters which allows it to contribute even to precision approaches.

In contrast, GPS satellites normally operate at 3 meters UDRE, the
best accuracy WAAS allows any ranging source to achieve.

PRN133 has been performing at UDRE of 50 with some degradation to 150.

This is most useful in South America since PRN133 has the best view of
South America of all GEOs, and with a WAAS compatible receiver capable
of tracking two SBAS GEOs, you would effectively get two extra GPS
satellites.

I suppose at least you can use 133 for integrity information for the
rest of the satellites - at least those visible and monitored in N.A.

But the WAAS differential correction would not be applied in S.A. and
the range error from 133 would pollute GPS-only nav solutions in any
case - fine for terminals and en-route only.

--
gmail originated posts filtered due to spam.

On Oct 30, 4:44*pm, macpacheco wrote:

NASA JPL operates a Global Differential GPS system with worldwide
coverage. They claim 10cm performance.

http://www.gdgps.net/

'The NASA Global Differential GPS (GDGPS) System is a complete, highly
accurate, and extremely robust real-time GPS monitoring and
augmentation system'.

I believe the John Deere Starfire commercial service is based upon the
NASA system.

Why can't airplanes use it ?

--- CHAS

On Oct 30, 10:08*pm, HIPAR wrote:
On Oct 30, 4:44*pm, macpacheco wrote:

NASA JPL operates a Global Differential GPS system with worldwide
coverage. *They claim 10cm performance.

http://www.gdgps.net/

'The NASA Global Differential GPS (GDGPS) System is a complete, highly
accurate, and extremely robust real-time GPS monitoring and
augmentation system'.

I believe the John Deere Starfire commercial service is based upon the
NASA system.

Why can't airplanes use it ?

--- *CHAS

- 10 cm performance in real time kinematic or post processing ?

- 10 cm performance at what confidence level ? SBAS confidence levels
are 99.99% - 99.99999% performance, instead of the usual 50-95%.

- Any system with that kind of performance today HAS to use semi
codeless at the end user level (L2 band). The FAA/ICAO/EASA has this
ARNS paranoia mentality that considers any usage of signals outside
ARNS protected bands a BIG no-no for end user equipment. While I don't
agree, I understand that decision within their paranoia mentality.
That's because the biggest bottleneck in SBAS performance today is
IONO corrections that must be applied on a grid basis, SoL end users
can't use semi codeless for autonomous IONO corrections. SBAS iono
grids are broadcast on a 5x5 degree spacing, and their calculation is
extremely dependent on station density.

- Finally, end user receivers are not required to have extensive multi
path rejection, that's the second biggest error factor in SBAS.

- If SBAS end users were allowed to use semi codeless today, and L2C /
L5 as it became healthy for IONO corrections, the current VPL/HPL
(vertical/horizontal protection level) that range from 15-50 meters
today, would go down to 5-20 meters easily, but that's 5 meters at
99.999% level (or better), which easily means measured performance
would be sub-meter. Add extensive multi path rejection requirement and
UDRE would come down from 3 meters to 1.5 meters easily. With
protection levels in the 2-10 meters range. UDRE level includes a
multi path error budget for end user equipment. A smarter approach
would have been to exclude receiver errors from UDRE levels, and
determine receiver errors (including multipath) at equipment
certification time, and have the end user equipment add its own error
to the UDRE levels, providing for a more competitive landscape for
equipments with better multi path rejection (would be able to achieve
LPV200 approaches under scenarios that are forbidden today, and could
even provide a basis for CAT II approaches today).

Theoretically if you plug in SBAS corrections into an end user
receiver that uses the starfire logic, you should get half meter
performance or better. The difference is due to the absence of carrier
phase information in the SBAS data stream.

SBAS uses a 250bps data stream, if you remove the IONO grid from that
data stream, you take 80% of the data away, which would allow for a
five fold increase in clock/ephemeris updates. Or you could easily add
carrier phase information and still increase the update rate. LAAS has
carrier phase information for instance.

Finally, SBAS ephemeris/clock updates accuracy would improve
significantly if all SBAS systems use each other's pseudoranging, in
WAAS cases that would mean at least using three strategically selected
MSAS stations and four strategically selected EGNOS stations, allowing
for almost worldwide ephemeris/clock coverage. Today satellites flying
over the Indian Ocean get Not Monitored flags in WAAS, while
satellites over the south pacific get NM flags on EGNOS. EGNOS fares a
little better due to having one station in South Africa and one in
French Guyana (South America very close to the equator line).

If all SBAS systems used 100% of each other reference stations, they
would be able to provide worldwide clock/ephemeris updates (all
satellites) at UDRE 3 for all satellites north of 30S latitude and
mostly UDRE 3 for satellites south of that line.

Marcelo Pacheco

On 2011-10-30 20:08 , HIPAR wrote:
On Oct 30, 4:44 pm, wrote:

NASA JPL operates a Global Differential GPS system with worldwide
coverage. They claim 10cm performance.

http://www.gdgps.net/

'The NASA Global Differential GPS (GDGPS) System is a complete, highly
accurate, and extremely robust real-time GPS monitoring and
augmentation system'.

I believe the John Deere Starfire commercial service is based upon the
NASA system.

Why can't airplanes use it ?

First off it's proprietary - something WAAS/EGNOS avoid. Airlines are
loathe to add equipment and pay operating fees for it. (Not to mention
that JD would have to build (or have an avionics firm design, build and
certify) airborne Starfire receivers.

Secondly, Starfire receivers are L1+L2. More expensive than L1
receivers. L1+L2(codeless) phase comparisons provide for a lot of local
PR correction due to ionospheric delays. The data downloaded by
Starfire is thus limited to non-iono effects (ephemeris error, clock error).

So, an aviation certified L1/L2 antenna would be needed as well (I don't
know if any exist but surely a military antenna could be put through the
paces for DO-160D and whichever TSO applies to GPS antennas,
appropriately modified to cover L2 reception).

It doesn't provide (I assume) integrity signals - though likely it could
with little additional effort.

Aparently Starfire also uses the WAAS ephemeris/clock data even if it is
not as accurate as Starfire's own eph/clk data.

Finally, there may be various forms of liability issues both on the part
of JD and the national airspace services.

--
gmail originated posts filtered due to spam.

On Oct 31, 11:56*am, Alan Browne
wrote:
On 2011-10-30 20:08 , HIPAR wrote:

On Oct 30, 4:44 pm, *wrote:

NASA JPL operates a Global Differential GPS system with worldwide
coverage. *They claim 10cm performance.

http://www.gdgps.net/

'The NASA Global Differential GPS (GDGPS) System is a complete, highly
accurate, and extremely robust real-time GPS monitoring and
augmentation system'.

I believe the John Deere Starfire commercial service is based upon the
NASA system.

Why can't airplanes use it ?

First off it's proprietary - something WAAS/EGNOS avoid. *Airlines are
loathe to add equipment and pay operating fees for it. *(Not to mention
that JD would have to build (or have an avionics firm design, build and
certify) airborne Starfire receivers.

Secondly, Starfire receivers are L1+L2. *More expensive than L1
receivers. *L1+L2(codeless) phase comparisons provide for a lot of local
PR correction due to ionospheric delays. *The data downloaded by
Starfire is thus limited to non-iono effects (ephemeris error, clock error).

So, an aviation certified L1/L2 antenna would be needed as well (I don't
know if any exist but surely a military antenna could be put through the
paces for DO-160D and whichever TSO applies to GPS antennas,
appropriately modified to cover L2 reception).

It doesn't provide (I assume) integrity signals - though likely it could
with little additional effort.

Aparently Starfire also uses the WAAS ephemeris/clock data even if it is
not as accurate as Starfire's own eph/clk data.

Finally, there may be various forms of liability issues both on the part
of JD and the national airspace services.

--
gmail originated posts filtered due to spam.

L2 isn't ARNS protected, so they are forbidden for aviation SBAS
receivers.
The only means for IONO corrections on SBAS receivers will be with L1/
L5, both in ARNS protected band, hence the importance of GPS L5
becoming operational for dual frequency SBAS (we might get Galileo
operational prior to GPS L5, and use Galileo dual frequency + GPS
single frequency for EGNOS).

On 2011-11-01 02:34 , macpacheco wrote:
On Oct 31, 11:56 am, Alan
wrote:
On 2011-10-30 20:08 , HIPAR wrote:

On Oct 30, 4:44 pm, wrote:

NASA JPL operates a Global Differential GPS system with worldwide
coverage. They claim 10cm performance.

http://www.gdgps.net/

'The NASA Global Differential GPS (GDGPS) System is a complete, highly
accurate, and extremely robust real-time GPS monitoring and
augmentation system'.

I believe the John Deere Starfire commercial service is based upon the
NASA system.

Why can't airplanes use it ?

First off it's proprietary - something WAAS/EGNOS avoid. Airlines are
loathe to add equipment and pay operating fees for it. (Not to mention
that JD would have to build (or have an avionics firm design, build and
certify) airborne Starfire receivers.

Secondly, Starfire receivers are L1+L2. More expensive than L1
receivers. L1+L2(codeless) phase comparisons provide for a lot of local
PR correction due to ionospheric delays. The data downloaded by
Starfire is thus limited to non-iono effects (ephemeris error, clock error).

So, an aviation certified L1/L2 antenna would be needed as well (I don't
know if any exist but surely a military antenna could be put through the
paces for DO-160D and whichever TSO applies to GPS antennas,
appropriately modified to cover L2 reception).

It doesn't provide (I assume) integrity signals - though likely it could
with little additional effort.

Aparently Starfire also uses the WAAS ephemeris/clock data even if it is
not as accurate as Starfire's own eph/clk data.

Finally, there may be various forms of liability issues both on the part
of JD and the national airspace services.

--
gmail originated posts filtered due to spam.

L2 isn't ARNS protected, so they are forbidden for aviation SBAS
receivers.

I was just answering HIPAR's general question. The same list applies to
L5 use as well. Of course L5 birds are rare so it will be a long time
before there are enough for actual aviation use.

The only means for IONO corrections on SBAS receivers will be with L1/
L5, both in ARNS protected band, hence the importance of GPS L5
becoming operational for dual frequency SBAS (we might get Galileo
operational prior to GPS L5, and use Galileo dual frequency + GPS
single frequency for EGNOS).

L5 isn't exactly usable yet with all of 2 sats in orbit. Will be a long
wait before any advance with any system. For simplicity sake (a good
thing in avionics) mixing GPS with EGNOS in a system won't be seen in
avionics for quite a while yet.

--
gmail originated posts filtered due to spam.

On 2011-11-01 09:25 , Alan Browne wrote:
On 2011-11-01 02:34 , macpacheco wrote:
On Oct 31, 11:56 am, Alan
wrote:
On 2011-10-30 20:08 , HIPAR wrote:

On Oct 30, 4:44 pm, wrote:

NASA JPL operates a Global Differential GPS system with worldwide
coverage. They claim 10cm performance.

http://www.gdgps.net/

'The NASA Global Differential GPS (GDGPS) System is a complete, highly
accurate, and extremely robust real-time GPS monitoring and
augmentation system'.

I believe the John Deere Starfire commercial service is based upon the
NASA system.

Why can't airplanes use it ?

First off it's proprietary - something WAAS/EGNOS avoid. Airlines are
loathe to add equipment and pay operating fees for it. (Not to mention
that JD would have to build (or have an avionics firm design, build and
certify) airborne Starfire receivers.

Secondly, Starfire receivers are L1+L2. More expensive than L1
receivers. L1+L2(codeless) phase comparisons provide for a lot of local
PR correction due to ionospheric delays. The data downloaded by
Starfire is thus limited to non-iono effects (ephemeris error, clock
error).

So, an aviation certified L1/L2 antenna would be needed as well (I don't
know if any exist but surely a military antenna could be put through the
paces for DO-160D and whichever TSO applies to GPS antennas,
appropriately modified to cover L2 reception).

It doesn't provide (I assume) integrity signals - though likely it could
with little additional effort.

Aparently Starfire also uses the WAAS ephemeris/clock data even if it is
not as accurate as Starfire's own eph/clk data.

Finally, there may be various forms of liability issues both on the part
of JD and the national airspace services.

--
gmail originated posts filtered due to spam.

L2 isn't ARNS protected, so they are forbidden for aviation SBAS
receivers.

I was just answering HIPAR's general question. The same list applies to
L5 use as well. Of course L5 birds are rare so it will be a long time
before there are enough for actual aviation use.

The only means for IONO corrections on SBAS receivers will be with L1/
L5, both in ARNS protected band, hence the importance of GPS L5
becoming operational for dual frequency SBAS (we might get Galileo
operational prior to GPS L5, and use Galileo dual frequency + GPS
single frequency for EGNOS).

L5 isn't exactly usable yet with all of 2 sats in orbit. Will be a long
wait before any advance with any system. For simplicity sake (a good
thing in avionics) mixing GPS with EGNOS in a system won't be seen in
..............
avionics for quite a while yet.

Sorry - meant to say mixing GPS with Galileo.


--
gmail originated posts filtered due to spam.

On Nov 1, 1:18*pm, Alan Browne
wrote:
On 2011-11-01 09:25 , Alan Browne wrote:







On 2011-11-01 02:34 , macpacheco wrote:
On Oct 31, 11:56 am, Alan
wrote:
On 2011-10-30 20:08 , HIPAR wrote:

On Oct 30, 4:44 pm, wrote:

NASA JPL operates a Global Differential GPS system with worldwide
coverage. They claim 10cm performance.

http://www.gdgps.net/

'The NASA Global Differential GPS (GDGPS) System is a complete, highly
accurate, and extremely robust real-time GPS monitoring and
augmentation system'.

I believe the John Deere Starfire commercial service is based upon the
NASA system.

Why can't airplanes use it ?

First off it's proprietary - something WAAS/EGNOS avoid. Airlines are
loathe to add equipment and pay operating fees for it. (Not to mention
that JD would have to build (or have an avionics firm design, build and
certify) airborne Starfire receivers.

Secondly, Starfire receivers are L1+L2. More expensive than L1
receivers. L1+L2(codeless) phase comparisons provide for a lot of local
PR correction due to ionospheric delays. The data downloaded by
Starfire is thus limited to non-iono effects (ephemeris error, clock
error).

So, an aviation certified L1/L2 antenna would be needed as well (I don't
know if any exist but surely a military antenna could be put through the
paces for DO-160D and whichever TSO applies to GPS antennas,
appropriately modified to cover L2 reception).

It doesn't provide (I assume) integrity signals - though likely it could
with little additional effort.

Aparently Starfire also uses the WAAS ephemeris/clock data even if it is
not as accurate as Starfire's own eph/clk data.

Finally, there may be various forms of liability issues both on the part
of JD and the national airspace services.

--
gmail originated posts filtered due to spam.

L2 isn't ARNS protected, so they are forbidden for aviation SBAS
receivers.

I was just answering HIPAR's general question. The same list applies to
L5 use as well. Of course L5 birds are rare so it will be a long time
before there are enough for actual aviation use.

The only means for IONO corrections on SBAS receivers will be with L1/
L5, both in ARNS protected band, hence the importance of GPS L5
becoming operational for dual frequency SBAS (we might get Galileo
operational prior to GPS L5, and use Galileo dual frequency + GPS
single frequency for EGNOS).

L5 isn't exactly usable yet with all of 2 sats in orbit. Will be a long
wait before any advance with any system. For simplicity sake (a good
thing in avionics) mixing GPS with EGNOS in a system won't be seen in

* * * * * * * * * * * * * * *..............

avionics for quite a while yet.

Sorry - meant to say mixing GPS with Galileo.

The FAA stated that GPS L5 WAAS will only be allowed once GPS L5 is
FOC, so 22 GPS launches to go before we get there. This was reiterated
in the current issue of FAA Sat Nav News (issued in the last few
days).

One of the reasons is they will replace the whole thing, all reference
receivers will then work only with L1+L5, all current ground semi
codeless will go at once, so once they migrate to L5 for the ground
infrastructure, even GPS IIR-M will no longer be used for WAAS.

It will be a temporary big step backwards, cause we'll go from using
all operational GPS satellites to using only L5 capable satellites,
reducing from 29-31 operational satellites to 24 initially.

That's stupid in my opinion, but that's their prerogative, they should
include support for L2C for the ground receivers, using L2C for IIR-M
and L5 for IIF + III, that would keep 29+ birds usable at all times.
And Galileo + Glonass should be rolled into WAAS as well.

That's only for aviation, other receivers outside the FAA's authority
could even use semi codeless today with any SBAS.

As far as Galileo or Glonass support for WAAS, theres no word
whatsoever in adding WAAS support for that, but the ARAIM work (which
makes WAAS obsolete) would include multi constellation end user
support.

On Nov 1, 9:25*am, Alan Browne
wrote:

....

L5 isn't exactly usable yet with all of 2 sats in orbit. *Will be a long
wait before any advance with any system. *For simplicity sake (a good
thing in avionics) mixing GPS with EGNOS in a system won't be seen in
avionics for quite a while yet.

--

I couldn't agree more that we need simplicity .. too many
constellations transmitting signals that are compatible only by the
definition of not interfering with each other. My head would be
spinning if I were tasked to perform a trade study defining the next
generation of avionics. But the GNSS community thinks this kind of
diversity is great so those geniuses like Marcelo (just joking) can
sort it out.

Would it have been nice if Galileo L5 and NAVSTAR L5 shared a common
ICD? Would it have been nice if there were a common L1 modernized
signal. That would be 'bound' the problem.

Regarding WDGPS, I really don't understand who actually controls
access to the system. If NASA operates the core system, what kind of
agreement does the US government have with Deere allowing them
exclusive commercial marketing rights under the Starfire trademark?
NASA/JPL doesn't say much about that.

I looked over a few of the easier to read references concerning the
JPL system. This one addresses the expected performance for a GDGPS
corrected C/A code system:

http://www.gdgps.net/system-desc/pap...leFreqCorr.pdf

Receiving L1 only, I'd say it might provide WAAS grade performance.
Getting back to simplicity, the need to receive the corrections from
another satellite system would complicate the actual operations.
Along with the other issues discussed, WAAS remains a more practical
system for airplanes.

--- CHAS