GPS Altitude with WAAS

The pigs will be flying long before there is a 5F day at OAK.

Mike
MU-2


"Fred E. Pate" wrote in message
...
John Bell wrote:
Let me add two links to the discussion:

This is on problems with cold weather altimetry:

http://www.aircraftbuyer.com/learn/train06.htm

This is about the accuracy of unaided GPS altitude in the context of
vertical guidance, but it bears some relavence to the discussion of the
accuracy of GPS altitude:

http://www.bluecoat.org/reports/Graham_2001_RawGPS.pdf

John Bell
www.cockpitgps.com


This one's for the Canadians on this thread. A notice on the new
Oakland, California (KOAK) "RNAV (GPS) RWY 29" approach
(http://www.myairplane.com/databases/.../OAK_agr29.pdf):

"BARO-VNAV NA below -15 deg C (5 deg F)"

And this is for a decision altitude of only 294 ft AGL. Seems like the
FAA is moving towards taking into account temperature errors in
barometric alitmetry. And, by implication, this supports the premise
that WAAS altitude figures are more accurate than the trusty old
"sensitive altimeter." (In the legend they specifically state that
WAAS-based VNAV can be used when BARO-VNAV is not approved due to
temperature.)

Sure, but that's not tne point. These restrictions will be standard on all of these types of approaches nation wide. Its the first time I am aware of that the FAA has included temperature altimetry errors in instrument procedures.

Mike Rapoport wrote:


The pigs will be flying long before there is a 5F day at OAK.

Mike
MU-2


"Fred E. Pate" wrote in message
...
John Bell wrote:
Let me add two links to the discussion:

This is on problems with cold weather altimetry:

http://www.aircraftbuyer.com/learn/train06.htm

This is about the accuracy of unaided GPS altitude in the context of
vertical guidance, but it bears some relavence to the discussion of the
accuracy of GPS altitude:

http://www.bluecoat.org/reports/Graham_2001_RawGPS.pdf

John Bell
www.cockpitgps.com


This one's for the Canadians on this thread. A notice on the new
Oakland, California (KOAK) "RNAV (GPS) RWY 29" approach
(http://www.myairplane.com/databases/.../OAK_agr29.pdf):

"BARO-VNAV NA below -15 deg C (5 deg F)"

And this is for a decision altitude of only 294 ft AGL. Seems like the
FAA is moving towards taking into account temperature errors in
barometric alitmetry. And, by implication, this supports the premise
that WAAS altitude figures are more accurate than the trusty old
"sensitive altimeter." (In the legend they specifically state that
WAAS-based VNAV can be used when BARO-VNAV is not approved due to
temperature.)

I agree in principle but in actuality it never gets cold enough in the US to
make a difference. The only times that we have really low temperatures (-40
and below) there is an inversion.

Mike
MU-2


wrote in message ...
Sure, but that's not tne point. These restrictions will be standard on
all of these types of approaches nation wide. Its the first time I am aware
of that the FAA has included temperature altimetry errors in instrument
procedures.

Mike Rapoport wrote:


The pigs will be flying long before there is a 5F day at OAK.

Mike
MU-2


"Fred E. Pate" wrote in message
...
John Bell wrote:
Let me add two links to the discussion:

This is on problems with cold weather altimetry:

http://www.aircraftbuyer.com/learn/train06.htm

This is about the accuracy of unaided GPS altitude in the context of
vertical guidance, but it bears some relavence to the discussion of
the
accuracy of GPS altitude:

http://www.bluecoat.org/reports/Graham_2001_RawGPS.pdf

John Bell
www.cockpitgps.com


This one's for the Canadians on this thread. A notice on the new
Oakland, California (KOAK) "RNAV (GPS) RWY 29" approach
(http://www.myairplane.com/databases/.../OAK_agr29.pdf):

"BARO-VNAV NA below -15 deg C (5 deg F)"

And this is for a decision altitude of only 294 ft AGL. Seems like the
FAA is moving towards taking into account temperature errors in
barometric alitmetry. And, by implication, this supports the premise
that WAAS altitude figures are more accurate than the trusty old
"sensitive altimeter." (In the legend they specifically state that
WAAS-based VNAV can be used when BARO-VNAV is not approved due to
temperature.)

Okay. But if you're on a precision approach you'll be below the inversion, no?

Mike Rapoport wrote:


I agree in principle but in actuality it never gets cold enough in the US to
make a difference. The only times that we have really low temperatures (-40
and below) there is an inversion.

Mike
MU-2

Mike Rapoport wrote:
The pigs will be flying long before there is a 5F day at OAK.

Mike
MU-2

Oh yeah, I forgot to add that those pigs will be using WAAS and LAAS
equipment to make their approaches into Oakland when it happens