Gageteers, we need a digital heading sensor [Archive]

Bill Daniels

June 16th 04, 06:34 PM

I've been analyzing the IGC files from my flights and comparing them to
others.

Generally, in good conditions, I'm circling less than 25% of the time.
Other, far better pilots than I, are circling less than 15% of the time.
This means that wind data that depends on the glider flying circles gets way
out of date during the long glides. OK, "S" turns can give the computer a
chance to compute wind if you remember to fly them but there are still a lot
of long, straight glides.

To compute real-time wind data we need Groundspeed, Ground Track (any GPS
gives these)True Airspeed (Some computers do this if they have OAT, Pressure
Altitude and IAS) and accurate heading data. Heading data it the tough nut
to crack.

So, how do we get Heading? One way might be to put a GPS antenna in each
wing and look at the carrier phase difference. If the computer saw a
constant track, it could assume the wings are level and determine a heading
value. This heading value might update an aerospace quality MEMS heading
gyro that would maintain a flow of heading data to the glide computer during
times when the wings were banked.

With good heading data we could get uninterrupted high quality wind data
regardless of the gliders' maneuvering or lack of it.

OK, RAS gageteers, how about it?

Bill Daniels

David Starer

June 16th 04, 06:39 PM

For calculating a final glide, you only need to know the wind component
along the final track; it isn't actually necessary to know the absolute wind
strength and direction. The difference between true airspeed (corrected IAS)
and ground speed (from the GPS) is equal to the component you need, so the
glider's heading isn't required.

David Starer

"Bill Daniels" > wrote in message
news:gw%zc.59643$HG.25574@attbi_s53...
> I've been analyzing the IGC files from my flights and comparing them to
> others.
>
> Generally, in good conditions, I'm circling less than 25% of the time.
> Other, far better pilots than I, are circling less than 15% of the time.
> This means that wind data that depends on the glider flying circles gets
way
> out of date during the long glides. OK, "S" turns can give the computer a
> chance to compute wind if you remember to fly them but there are still a
lot
> of long, straight glides.
>
> To compute real-time wind data we need Groundspeed, Ground Track (any GPS
> gives these)True Airspeed (Some computers do this if they have OAT,
Pressure
> Altitude and IAS) and accurate heading data. Heading data it the tough
nut
> to crack.
>
> So, how do we get Heading? One way might be to put a GPS antenna in each
> wing and look at the carrier phase difference. If the computer saw a
> constant track, it could assume the wings are level and determine a
heading
> value. This heading value might update an aerospace quality MEMS heading
> gyro that would maintain a flow of heading data to the glide computer
during
> times when the wings were banked.
>
> With good heading data we could get uninterrupted high quality wind data
> regardless of the gliders' maneuvering or lack of it.
>
> OK, RAS gageteers, how about it?
>
> Bill Daniels
>

Bill Daniels

June 16th 04, 07:33 PM

Partly true. If you have a 35 knot 90 degree crosswind, the wind component
along the final glide path is zero. However the penalty for crabbing into
that crosswind to maintain your course to the finish line is significant.

My concern is mountain flying. Mountain winds tend to change a lot in a
short distance. The sooner you know of a wind shift the easier it is to
take advantage of it. I still want highly accurate real-time wind data.

Bill Daniels

"David Starer" > wrote in message
...
> For calculating a final glide, you only need to know the wind component
> along the final track; it isn't actually necessary to know the absolute
wind
> strength and direction. The difference between true airspeed (corrected
IAS)
> and ground speed (from the GPS) is equal to the component you need, so the
> glider's heading isn't required.
>
> David Starer
>
> "Bill Daniels" > wrote in message
> news:gw%zc.59643$HG.25574@attbi_s53...
> > I've been analyzing the IGC files from my flights and comparing them to
> > others.
> >
> > Generally, in good conditions, I'm circling less than 25% of the time.
> > Other, far better pilots than I, are circling less than 15% of the time.
> > This means that wind data that depends on the glider flying circles gets
> way
> > out of date during the long glides. OK, "S" turns can give the computer
a
> > chance to compute wind if you remember to fly them but there are still a
> lot
> > of long, straight glides.
> >
> > To compute real-time wind data we need Groundspeed, Ground Track (any
GPS
> > gives these)True Airspeed (Some computers do this if they have OAT,
> Pressure
> > Altitude and IAS) and accurate heading data. Heading data it the tough
> nut
> > to crack.
> >
> > So, how do we get Heading? One way might be to put a GPS antenna in
each
> > wing and look at the carrier phase difference. If the computer saw a
> > constant track, it could assume the wings are level and determine a
> heading
> > value. This heading value might update an aerospace quality MEMS
heading
> > gyro that would maintain a flow of heading data to the glide computer
> during
> > times when the wings were banked.
> >
> > With good heading data we could get uninterrupted high quality wind data
> > regardless of the gliders' maneuvering or lack of it.
> >
> > OK, RAS gageteers, how about it?
> >
> > Bill Daniels
> >
>
>

David Starer

June 16th 04, 07:50 PM

Bill,

Sorry to disagree but a quick calculation shows that if you glide at 70
knots in a 35 knot 90 degree crosswind, you will experience the equivalent
of about 8 kts headwind component. This is the figure you would have to feed
into the calculation to find the height needed to complete your final glide.

David Starer

"Bill Daniels" > wrote in message
news:An0Ac.50845$0y.34865@attbi_s03...
> Partly true. If you have a 35 knot 90 degree crosswind, the wind
component
> along the final glide path is zero. However the penalty for crabbing into
> that crosswind to maintain your course to the finish line is significant.
>
> My concern is mountain flying. Mountain winds tend to change a lot in a
> short distance. The sooner you know of a wind shift the easier it is to
> take advantage of it. I still want highly accurate real-time wind data.
>
> Bill Daniels
>
> "David Starer" > wrote in message
> ...
> > For calculating a final glide, you only need to know the wind component
> > along the final track; it isn't actually necessary to know the absolute
> wind
> > strength and direction. The difference between true airspeed (corrected
> IAS)
> > and ground speed (from the GPS) is equal to the component you need, so
the
> > glider's heading isn't required.
> >
> > David Starer
> >
> > "Bill Daniels" > wrote in message
> > news:gw%zc.59643$HG.25574@attbi_s53...
> > > I've been analyzing the IGC files from my flights and comparing them
to
> > > others.
> > >
> > > Generally, in good conditions, I'm circling less than 25% of the time.
> > > Other, far better pilots than I, are circling less than 15% of the
time.
> > > This means that wind data that depends on the glider flying circles
gets
> > way
> > > out of date during the long glides. OK, "S" turns can give the
computer
> a
> > > chance to compute wind if you remember to fly them but there are still
a
> > lot
> > > of long, straight glides.
> > >
> > > To compute real-time wind data we need Groundspeed, Ground Track (any
> GPS
> > > gives these)True Airspeed (Some computers do this if they have OAT,
> > Pressure
> > > Altitude and IAS) and accurate heading data. Heading data it the
tough
> > nut
> > > to crack.
> > >
> > > So, how do we get Heading? One way might be to put a GPS antenna in
> each
> > > wing and look at the carrier phase difference. If the computer saw a
> > > constant track, it could assume the wings are level and determine a
> > heading
> > > value. This heading value might update an aerospace quality MEMS
> heading
> > > gyro that would maintain a flow of heading data to the glide computer
> > during
> > > times when the wings were banked.
> > >
> > > With good heading data we could get uninterrupted high quality wind
data
> > > regardless of the gliders' maneuvering or lack of it.
> > >
> > > OK, RAS gageteers, how about it?
> > >
> > > Bill Daniels
> > >
> >
> >
>

Bill Daniels

June 16th 04, 08:47 PM

OK, David, I hope you are right.

However, if the computer doesn't know the glider's heading, how does it
solve the wind triangle without turns? If the computer can't solve for the
true wind data how can it compute the headwind component?

People keep telling me that TAS + or - Groundspeed will give a "good enough"
headwind/tailwind component. My experience is that the wind data gets very
stale during a long final glide.
After a few circles to get fresh wind data, the final glide numbers look a
lot different. If the wind shifts or I descend through a wind layer, I need
to know it RIGHT NOW.

Bill Daniels

"David Starer" > wrote in message
...
> Bill,
>
> Sorry to disagree but a quick calculation shows that if you glide at 70
> knots in a 35 knot 90 degree crosswind, you will experience the equivalent
> of about 8 kts headwind component. This is the figure you would have to
feed
> into the calculation to find the height needed to complete your final
glide.
>
> David Starer
>
> "Bill Daniels" > wrote in message
> news:An0Ac.50845$0y.34865@attbi_s03...
> > Partly true. If you have a 35 knot 90 degree crosswind, the wind
> component
> > along the final glide path is zero. However the penalty for crabbing
into
> > that crosswind to maintain your course to the finish line is
significant.
> >
> > My concern is mountain flying. Mountain winds tend to change a lot in a
> > short distance. The sooner you know of a wind shift the easier it is to
> > take advantage of it. I still want highly accurate real-time wind data.
> >
> > Bill Daniels
> >
> > "David Starer" > wrote in message
> > ...
> > > For calculating a final glide, you only need to know the wind
component
> > > along the final track; it isn't actually necessary to know the
absolute
> > wind
> > > strength and direction. The difference between true airspeed
(corrected
> > IAS)
> > > and ground speed (from the GPS) is equal to the component you need, so
> the
> > > glider's heading isn't required.
> > >
> > > David Starer
> > >
> > > "Bill Daniels" > wrote in message
> > > news:gw%zc.59643$HG.25574@attbi_s53...
> > > > I've been analyzing the IGC files from my flights and comparing them
> to
> > > > others.
> > > >
> > > > Generally, in good conditions, I'm circling less than 25% of the
time.
> > > > Other, far better pilots than I, are circling less than 15% of the
> time.
> > > > This means that wind data that depends on the glider flying circles
> gets
> > > way
> > > > out of date during the long glides. OK, "S" turns can give the
> computer
> > a
> > > > chance to compute wind if you remember to fly them but there are
still
> a
> > > lot
> > > > of long, straight glides.
> > > >
> > > > To compute real-time wind data we need Groundspeed, Ground Track
(any
> > GPS
> > > > gives these)True Airspeed (Some computers do this if they have OAT,
> > > Pressure
> > > > Altitude and IAS) and accurate heading data. Heading data it the
> tough
> > > nut
> > > > to crack.
> > > >
> > > > So, how do we get Heading? One way might be to put a GPS antenna in
> > each
> > > > wing and look at the carrier phase difference. If the computer saw
a
> > > > constant track, it could assume the wings are level and determine a
> > > heading
> > > > value. This heading value might update an aerospace quality MEMS
> > heading
> > > > gyro that would maintain a flow of heading data to the glide
computer
> > > during
> > > > times when the wings were banked.
> > > >
> > > > With good heading data we could get uninterrupted high quality wind
> data
> > > > regardless of the gliders' maneuvering or lack of it.
> > > >
> > > > OK, RAS gageteers, how about it?
> > > >
> > > > Bill Daniels
> > > >
> > >
> > >
> >
>
>

Eric Greenwell

June 16th 04, 09:26 PM

Bill Daniels wrote:
> OK, David, I hope you are right.
>
> However, if the computer doesn't know the glider's heading, how does it
> solve the wind triangle without turns? If the computer can't solve for the
> true wind data how can it compute the headwind component?

The "headwind" = TAS - (Ground speed). It's the "effective" headwind
along your course (GPS ground track), not the actual headwind on the
glider's heading.

>
> People keep telling me that TAS + or - Groundspeed will give a "good enough"
> headwind/tailwind component. My experience is that the wind data gets very
> stale during a long final glide.

Yes, and a way to handle in some glide computers is to manually update
the wind value in use, using the measured "effective" headwind.

> After a few circles to get fresh wind data, the final glide numbers look a
> lot different. If the wind shifts or I descend through a wind layer, I need
> to know it RIGHT NOW.

The effective "headwind" seems to do this quite well, based on my
experience with a 302 and Glide Navigator (GN). GN also displays the
error between the effective headwind and the headwind calculated using
the last vector wind determination. If the error is more than a knot or
two, I know the vector wind has changed.

Of course, knowing it's changed doesn't tell you what it is, but once
alerted, I can circle or deviate my course to pick up the new vector
wind. For mountain flying, I'm often turning frequently anyway, so it
hasn't been the problem that the long straight glides in the open
sometimes are. Still, having an update to the vector wind every 20
seconds or so would be a nice.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Eric Greenwell

June 16th 04, 11:16 PM

Todd Pattist wrote:

> "David Starer" > wrote:
>
>
>>a quick calculation shows that if you glide at 70
>>knots in a 35 knot 90 degree crosswind, you will experience the equivalent
>>of about 8 kts headwind component. This is the figure you would have to feed
>>into the calculation to find the height needed to complete your final glide.
>
>
> 1) It's not at all unusual for me to be high enough to final
> glide to a TP, then turn and glide home. I need more than a
> component of the wind to figure out if I can make it to the
> TP and then home.

If the wind is changing along your course, knowing it accurately right
at the moment probably won't help much. You'll still be guessing about
the wind along the rest of the course, 10-20-30 minutes later. I suggest
using the headwind component for the entire final glide.

>
> 2) To figure out which of five potential airports in the
> area you can safely get to with maximum remaining altitude
> needs more than the wind component along your current glide
> path.

Since you can easily make the turnpoint, this won't be an issue until
you reach it. When you make the turn at the turnpoint, the computer
will update the vector wind. This should improve the glide calculations
to your safety airports. If you have head for one, you can go back the
headwind value to improve the calculations.

>
> 3) I'm gliding down to the ridge from thermals and expect to
> arrive low over relatively poor landability terrain. I'd
> really like that real time wind speed and direction to
> comfort my fearful heart as I dump off precious altitude and
> descend to the ridge.

I think this is the kind of short term (a minute or two) situation -
getting close to the ridge where you either need to turn away or
continue - that wind updates every 10-20 seconds would be useful. The
other situations involved long (30-40 minutes) glides during which the
wind could change several times.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Andy Durbin

June 16th 04, 11:51 PM

"David Starer" > wrote in message >...
> For calculating a final glide, you only need to know the wind component
> along the final track; it isn't actually necessary to know the absolute wind
> strength and direction. The difference between true airspeed (corrected IAS)
> and ground speed (from the GPS) is equal to the component you need, so the
> glider's heading isn't required.
>
> David Starer

This is only true if you can wait for the solution until you are
established on the final glide from the last turnpoint. Most of us
want the solution before rounding the last point, or perhaps even
before the last several turnpoints if working close in points to use
up a good last thermal on a MAT or PST. The wind direction and
magnitude are both required to derive that solution.

Andy

Dave Nadler YO

June 17th 04, 04:04 AM

Bill - The heading is not required. In the ILEC SN10 we do this
without heading, and it normally has the wind by the time you're
off tow. Pilot feedback and measurements indicate that we do
it quite accurately. We just use TAS and GPS ground track over
multiple observations (TAS requiring accurate IAS, press, temp).
Best Regards, Dave "YO"

"Bill Daniels" > wrote in message news:<gw%zc.59643$HG.25574@attbi_s53>...
> I've been analyzing the IGC files from my flights and comparing them to
> others.
>
> Generally, in good conditions, I'm circling less than 25% of the time.
> Other, far better pilots than I, are circling less than 15% of the time.
> This means that wind data that depends on the glider flying circles gets way
> out of date during the long glides. OK, "S" turns can give the computer a
> chance to compute wind if you remember to fly them but there are still a lot
> of long, straight glides.
>
> To compute real-time wind data we need Groundspeed, Ground Track (any GPS
> gives these)True Airspeed (Some computers do this if they have OAT, Pressure
> Altitude and IAS) and accurate heading data. Heading data it the tough nut
> to crack.
>
> So, how do we get Heading? One way might be to put a GPS antenna in each
> wing and look at the carrier phase difference. If the computer saw a
> constant track, it could assume the wings are level and determine a heading
> value. This heading value might update an aerospace quality MEMS heading
> gyro that would maintain a flow of heading data to the glide computer during
> times when the wings were banked.
>
> With good heading data we could get uninterrupted high quality wind data
> regardless of the gliders' maneuvering or lack of it.
>
> OK, RAS gageteers, how about it?
>
> Bill Daniels

Bill Daniels

June 17th 04, 04:51 AM

Dave, can it give highly accurate, real-time wind data, second by second on
a straight one hour glide?

My last flight showed this problem during a long glide. For 30 miles the
wind data showed SW winds at 20 knots but then I noticed the glider drifting
to the west. Two 360 turns and the computer showed wind at 090 at 10 knots.
When I crossed the wind shift line I had a chance to change strategy. 30
miles later when the wind error became obvious it was too late.

More and more I think we need very accurate real-time wind data with no
requirement to be constantly changing heading. A cheap, reliable heading
sensor would make this possible.

Bill Daniels

"Dave Nadler YO" > wrote in message
m...
> Bill - The heading is not required. In the ILEC SN10 we do this
> without heading, and it normally has the wind by the time you're
> off tow. Pilot feedback and measurements indicate that we do
> it quite accurately. We just use TAS and GPS ground track over
> multiple observations (TAS requiring accurate IAS, press, temp).
> Best Regards, Dave "YO"
>
> "Bill Daniels" > wrote in message
news:<gw%zc.59643$HG.25574@attbi_s53>...
> > I've been analyzing the IGC files from my flights and comparing them to
> > others.
> >
> > Generally, in good conditions, I'm circling less than 25% of the time.
> > Other, far better pilots than I, are circling less than 15% of the time.
> > This means that wind data that depends on the glider flying circles gets
way
> > out of date during the long glides. OK, "S" turns can give the computer
a
> > chance to compute wind if you remember to fly them but there are still a
lot
> > of long, straight glides.
> >
> > To compute real-time wind data we need Groundspeed, Ground Track (any
GPS
> > gives these)True Airspeed (Some computers do this if they have OAT,
Pressure
> > Altitude and IAS) and accurate heading data. Heading data it the tough
nut
> > to crack.
> >
> > So, how do we get Heading? One way might be to put a GPS antenna in
each
> > wing and look at the carrier phase difference. If the computer saw a
> > constant track, it could assume the wings are level and determine a
heading
> > value. This heading value might update an aerospace quality MEMS
heading
> > gyro that would maintain a flow of heading data to the glide computer
during
> > times when the wings were banked.
> >
> > With good heading data we could get uninterrupted high quality wind data
> > regardless of the gliders' maneuvering or lack of it.
> >
> > OK, RAS gageteers, how about it?
> >
> > Bill Daniels

f.blair

June 17th 04, 06:36 AM

Why can't the GPS create the 'heading data' my $90 Etrex gives a heading
reading.

"Bill Daniels" > wrote in message
news:_y8Ac.53766$0y.15362@attbi_s03...
> Dave, can it give highly accurate, real-time wind data, second by second
on
> a straight one hour glide?
>
> My last flight showed this problem during a long glide. For 30 miles the
> wind data showed SW winds at 20 knots but then I noticed the glider
drifting
> to the west. Two 360 turns and the computer showed wind at 090 at 10
knots.
> When I crossed the wind shift line I had a chance to change strategy. 30
> miles later when the wind error became obvious it was too late.
>
> More and more I think we need very accurate real-time wind data with no
> requirement to be constantly changing heading. A cheap, reliable heading
> sensor would make this possible.
>
> Bill Daniels
>
> "Dave Nadler YO" > wrote in message
> m...
> > Bill - The heading is not required. In the ILEC SN10 we do this
> > without heading, and it normally has the wind by the time you're
> > off tow. Pilot feedback and measurements indicate that we do
> > it quite accurately. We just use TAS and GPS ground track over
> > multiple observations (TAS requiring accurate IAS, press, temp).
> > Best Regards, Dave "YO"
> >
> > "Bill Daniels" > wrote in message
> news:<gw%zc.59643$HG.25574@attbi_s53>...
> > > I've been analyzing the IGC files from my flights and comparing them
to
> > > others.
> > >
> > > Generally, in good conditions, I'm circling less than 25% of the time.
> > > Other, far better pilots than I, are circling less than 15% of the
time.
> > > This means that wind data that depends on the glider flying circles
gets
> way
> > > out of date during the long glides. OK, "S" turns can give the
computer
> a
> > > chance to compute wind if you remember to fly them but there are still
a
> lot
> > > of long, straight glides.
> > >
> > > To compute real-time wind data we need Groundspeed, Ground Track (any
> GPS
> > > gives these)True Airspeed (Some computers do this if they have OAT,
> Pressure
> > > Altitude and IAS) and accurate heading data. Heading data it the
tough
> nut
> > > to crack.
> > >
> > > So, how do we get Heading? One way might be to put a GPS antenna in
> each
> > > wing and look at the carrier phase difference. If the computer saw a
> > > constant track, it could assume the wings are level and determine a
> heading
> > > value. This heading value might update an aerospace quality MEMS
> heading
> > > gyro that would maintain a flow of heading data to the glide computer
> during
> > > times when the wings were banked.
> > >
> > > With good heading data we could get uninterrupted high quality wind
data
> > > regardless of the gliders' maneuvering or lack of it.
> > >
> > > OK, RAS gageteers, how about it?
> > >
> > > Bill Daniels
>

David Starer

June 17th 04, 07:20 AM

The GPS gives TRACK, not HEADING. It can't tell what direction the glider is
pointing in, only the direction its motion is taking it across the ground.

David Starer

"f.blair" > wrote in message
news:E5aAc.44219$2i5.30680@attbi_s52...
> Why can't the GPS create the 'heading data' my $90 Etrex gives a heading
> reading.
>
> "Bill Daniels" > wrote in message
> news:_y8Ac.53766$0y.15362@attbi_s03...
> > Dave, can it give highly accurate, real-time wind data, second by second
> on
> > a straight one hour glide?
> >
> > My last flight showed this problem during a long glide. For 30 miles
the
> > wind data showed SW winds at 20 knots but then I noticed the glider
> drifting
> > to the west. Two 360 turns and the computer showed wind at 090 at 10
> knots.
> > When I crossed the wind shift line I had a chance to change strategy.
30
> > miles later when the wind error became obvious it was too late.
> >
> > More and more I think we need very accurate real-time wind data with no
> > requirement to be constantly changing heading. A cheap, reliable
heading
> > sensor would make this possible.
> >
> > Bill Daniels
> >
> > "Dave Nadler YO" > wrote in message
> > m...
> > > Bill - The heading is not required. In the ILEC SN10 we do this
> > > without heading, and it normally has the wind by the time you're
> > > off tow. Pilot feedback and measurements indicate that we do
> > > it quite accurately. We just use TAS and GPS ground track over
> > > multiple observations (TAS requiring accurate IAS, press, temp).
> > > Best Regards, Dave "YO"
> > >
> > > "Bill Daniels" > wrote in message
> > news:<gw%zc.59643$HG.25574@attbi_s53>...
> > > > I've been analyzing the IGC files from my flights and comparing them
> to
> > > > others.
> > > >
> > > > Generally, in good conditions, I'm circling less than 25% of the
time.
> > > > Other, far better pilots than I, are circling less than 15% of the
> time.
> > > > This means that wind data that depends on the glider flying circles
> gets
> > way
> > > > out of date during the long glides. OK, "S" turns can give the
> computer
> > a
> > > > chance to compute wind if you remember to fly them but there are
still
> a
> > lot
> > > > of long, straight glides.
> > > >
> > > > To compute real-time wind data we need Groundspeed, Ground Track
(any
> > GPS
> > > > gives these)True Airspeed (Some computers do this if they have OAT,
> > Pressure
> > > > Altitude and IAS) and accurate heading data. Heading data it the
> tough
> > nut
> > > > to crack.
> > > >
> > > > So, how do we get Heading? One way might be to put a GPS antenna in
> > each
> > > > wing and look at the carrier phase difference. If the computer saw
a
> > > > constant track, it could assume the wings are level and determine a
> > heading
> > > > value. This heading value might update an aerospace quality MEMS
> > heading
> > > > gyro that would maintain a flow of heading data to the glide
computer
> > during
> > > > times when the wings were banked.
> > > >
> > > > With good heading data we could get uninterrupted high quality wind
> data
> > > > regardless of the gliders' maneuvering or lack of it.
> > > >
> > > > OK, RAS gageteers, how about it?
> > > >
> > > > Bill Daniels
> >
>
>

Mark Navarre

June 17th 04, 07:51 AM

>Subject: Re: Gageteers, we need a digital heading sensor
>From: "Bill Daniels"

>My last flight showed this problem during a long glide. For 30 miles the
>wind data showed SW winds at 20 knots but then I noticed the glider drifting
>to the west. Two 360 turns and the computer showed wind at 090 at 10 knots.
>When I crossed the wind shift line I had a chance to change strategy. 30
>miles later when the wind error became obvious it was too late.
>
>More and more I think we need very accurate real-time wind data with no
>requirement to be constantly changing heading. A cheap, reliable heading
>sensor would make this possible.

I very strongly agree, because I too am "cursed" with long glides between
thermals when flying long cross country flights. Air masses may change
dramatically in 10's of miles, but you won't know if you don't stop for a few
turns, also late in the day shear lines come through and cannot be easily
spotted on blue days without real-time wind info. This info WILL make the
difference between getting there faster or slower (or getting there at all!).
If you don't understand this, then you either haven't flown 50-60+ mile glides,
or are just not observant enough of the situation to care.
Our climb instruments have evolved to the point that we really know what the
air is doing in the vertical direction, it would sure be nice to have as much
info about the horizontal direction.

-
Mark Navarre
2/5 black ace
LoCal, USA
remove brain to reply
-

Dave Nadler YO

June 17th 04, 12:09 PM

Bill, you're absolutely right, during a dead straight glide
with constant airspeed their isn't enough information to
compute the result. With an SN10 you need to make an S-turn
at least to get an update.

The heading sensor issue is a bit difficult. Certainly it can
be done with GPS using multiple antennas (I can't remember the
commercial products that do this off-hand). Google and you'll
find a few research projects using GPS for attitude as well
as heading. Cost is not on for gliders real soon. Compasses
are very cranky beasts, especially if they need to be glider-
pilot-proof (about which I could tell stories for hours).
Making something that is low-cost, self-calibrating, immune
to stupid installations - that's the hard bit.

Hope that all makes sense,
Best Regards, Dave

PS: Haven't seen anyone suggest a sun-tracker yet ?
Or vision-system with terrain matching ?

"Bill Daniels" > wrote in message news:<_y8Ac.53766$0y.15362@attbi_s03>...
> Dave, can it give highly accurate, real-time wind data, second by second on
> a straight one hour glide?
>
> My last flight showed this problem during a long glide. For 30 miles the
> wind data showed SW winds at 20 knots but then I noticed the glider drifting
> to the west. Two 360 turns and the computer showed wind at 090 at 10 knots.
> When I crossed the wind shift line I had a chance to change strategy. 30
> miles later when the wind error became obvious it was too late.
>
> More and more I think we need very accurate real-time wind data with no
> requirement to be constantly changing heading. A cheap, reliable heading
> sensor would make this possible.
>
> Bill Daniels
>
> "Dave Nadler YO" > wrote in message
> m...
> > Bill - The heading is not required. In the ILEC SN10 we do this
> > without heading, and it normally has the wind by the time you're
> > off tow. Pilot feedback and measurements indicate that we do
> > it quite accurately. We just use TAS and GPS ground track over
> > multiple observations (TAS requiring accurate IAS, press, temp).
> > Best Regards, Dave "YO"
> >
> > "Bill Daniels" > wrote in message
> news:<gw%zc.59643$HG.25574@attbi_s53>...
> > > I've been analyzing the IGC files from my flights and comparing them to
> > > others.
> > >
> > > Generally, in good conditions, I'm circling less than 25% of the time.
> > > Other, far better pilots than I, are circling less than 15% of the time.
> > > This means that wind data that depends on the glider flying circles gets
> way
> > > out of date during the long glides. OK, "S" turns can give the computer
> a
> > > chance to compute wind if you remember to fly them but there are still a
> lot
> > > of long, straight glides.
> > >
> > > To compute real-time wind data we need Groundspeed, Ground Track (any
> GPS
> > > gives these)True Airspeed (Some computers do this if they have OAT,
> Pressure
> > > Altitude and IAS) and accurate heading data. Heading data it the tough
> nut
> > > to crack.
> > >
> > > So, how do we get Heading? One way might be to put a GPS antenna in
> each
> > > wing and look at the carrier phase difference. If the computer saw a
> > > constant track, it could assume the wings are level and determine a
> heading
> > > value. This heading value might update an aerospace quality MEMS
> heading
> > > gyro that would maintain a flow of heading data to the glide computer
> during
> > > times when the wings were banked.
> > >
> > > With good heading data we could get uninterrupted high quality wind data
> > > regardless of the gliders' maneuvering or lack of it.
> > >
> > > OK, RAS gageteers, how about it?
> > >
> > > Bill Daniels

Clint

June 17th 04, 01:26 PM

> To compute real-time wind data we need Groundspeed, Ground Track (any GPS
> gives these)True Airspeed (Some computers do this if they have OAT, Pressure
> Altitude and IAS) and accurate heading data. Heading data it the tough nut
> to crack.
>
> So, how do we get Heading? One way might be to put a GPS antenna in each
> wing and look at the carrier phase difference. If the computer saw a
> constant track, it could assume the wings are level and determine a heading
> value. This heading value might update an aerospace quality MEMS heading
> gyro that would maintain a flow of heading data to the glide computer during
> times when the wings were banked.
>

The LX 5000 has the facility for a digital compass - precisely for the
reason that you are looking for a solution for. I have not used a
digital compass with my unit so I have no idea if it works better than
the other estimation methods used by the unit without a compass
attached.

Clinton
LAK 12

Bill Daniels

June 17th 04, 02:23 PM

"Dave Nadler YO" > wrote in message
om...
> Bill, you're absolutely right, during a dead straight glide
> with constant airspeed their isn't enough information to
> compute the result. With an SN10 you need to make an S-turn
> at least to get an update.
>
> The heading sensor issue is a bit difficult. Certainly it can
> be done with GPS using multiple antennas (I can't remember the
> commercial products that do this off-hand). Google and you'll
> find a few research projects using GPS for attitude as well
> as heading. Cost is not on for gliders real soon. Compasses
> are very cranky beasts, especially if they need to be glider-
> pilot-proof (about which I could tell stories for hours).
> Making something that is low-cost, self-calibrating, immune
> to stupid installations - that's the hard bit.
>
> Hope that all makes sense,
> Best Regards, Dave
>
> PS: Haven't seen anyone suggest a sun-tracker yet ?
> Or vision-system with terrain matching ?
>

Bob Lepp e-mailed me info on a company called Aventech that makes wind
direction detection equipment for crop dusters. These folks need very
accurate winds aloft data to predict the drift of chemicals sprayed on
crops.

Their gadget works just like a glider computer with the addition of a
two-antenna GPS array that provides heading data accurate to .5 degree. To
cover any gaps in the GPS signal, they use a solid state inertial unit.

Sensors that detect the earth's magnetic field will always be tricky. GPS
heading sensing looks like a winner since we need the GPS receiver anyway.
Maybe a couple of self-contained Bluetooth GPS receivers attached to the
wingtips would work. An inertial measurement unit would be very useful for
applications other than wind data. These could determine true vertical
regardless of the glider's attitude and very accurately measure Z-axis
acceleration. What vario maker wouldn't love to have that data.

No doubt this will be expensive at first but then we couldn't afford GPS 20
years ago. Twenty years before that glider pilots couldn't afford radios.
Electronics always seems to follow a learning curve that exponentially
reduces cost.

Bill Daniels

Bill Daniels

June 17th 04, 04:11 PM

This is what we need but smaller, cheaper, lighter and all other good things
engineering-wise.
http://www.xbow.com/Products/productsdetails.aspx?sid=104

Bill Daniels

"Dave Nadler YO" > wrote in message
om...
> Bill, you're absolutely right, during a dead straight glide
> with constant airspeed their isn't enough information to
> compute the result. With an SN10 you need to make an S-turn
> at least to get an update.
>
> The heading sensor issue is a bit difficult. Certainly it can
> be done with GPS using multiple antennas (I can't remember the
> commercial products that do this off-hand). Google and you'll
> find a few research projects using GPS for attitude as well
> as heading. Cost is not on for gliders real soon. Compasses
> are very cranky beasts, especially if they need to be glider-
> pilot-proof (about which I could tell stories for hours).
> Making something that is low-cost, self-calibrating, immune
> to stupid installations - that's the hard bit.
>
> Hope that all makes sense,
> Best Regards, Dave
>
> PS: Haven't seen anyone suggest a sun-tracker yet ?
> Or vision-system with terrain matching ?
>
> "Bill Daniels" > wrote in message
news:<_y8Ac.53766$0y.15362@attbi_s03>...
> > Dave, can it give highly accurate, real-time wind data, second by second
on
> > a straight one hour glide?
> >
> > My last flight showed this problem during a long glide. For 30 miles
the
> > wind data showed SW winds at 20 knots but then I noticed the glider
drifting
> > to the west. Two 360 turns and the computer showed wind at 090 at 10
knots.
> > When I crossed the wind shift line I had a chance to change strategy.
30
> > miles later when the wind error became obvious it was too late.
> >
> > More and more I think we need very accurate real-time wind data with no
> > requirement to be constantly changing heading. A cheap, reliable
heading
> > sensor would make this possible.
> >
> > Bill Daniels
> >
> > "Dave Nadler YO" > wrote in message
> > m...
> > > Bill - The heading is not required. In the ILEC SN10 we do this
> > > without heading, and it normally has the wind by the time you're
> > > off tow. Pilot feedback and measurements indicate that we do
> > > it quite accurately. We just use TAS and GPS ground track over
> > > multiple observations (TAS requiring accurate IAS, press, temp).
> > > Best Regards, Dave "YO"
> > >
> > > "Bill Daniels" > wrote in message
> > news:<gw%zc.59643$HG.25574@attbi_s53>...
> > > > I've been analyzing the IGC files from my flights and comparing them
to
> > > > others.
> > > >
> > > > Generally, in good conditions, I'm circling less than 25% of the
time.
> > > > Other, far better pilots than I, are circling less than 15% of the
time.
> > > > This means that wind data that depends on the glider flying circles
gets
> > way
> > > > out of date during the long glides. OK, "S" turns can give the
computer
> > a
> > > > chance to compute wind if you remember to fly them but there are
still a
> > lot
> > > > of long, straight glides.
> > > >
> > > > To compute real-time wind data we need Groundspeed, Ground Track
(any
> > GPS
> > > > gives these)True Airspeed (Some computers do this if they have OAT,
> > Pressure
> > > > Altitude and IAS) and accurate heading data. Heading data it the
tough
> > nut
> > > > to crack.
> > > >
> > > > So, how do we get Heading? One way might be to put a GPS antenna in
> > each
> > > > wing and look at the carrier phase difference. If the computer saw
a
> > > > constant track, it could assume the wings are level and determine a
> > heading
> > > > value. This heading value might update an aerospace quality MEMS
> > heading
> > > > gyro that would maintain a flow of heading data to the glide
computer
> > during
> > > > times when the wings were banked.
> > > >
> > > > With good heading data we could get uninterrupted high quality wind
data
> > > > regardless of the gliders' maneuvering or lack of it.
> > > >
> > > > OK, RAS gageteers, how about it?
> > > >
> > > > Bill Daniels

Paul Repacholi

June 17th 04, 04:47 PM

(Dave Nadler YO) writes:

> The heading sensor issue is a bit difficult. Certainly it can be
> done with GPS using multiple antennas (I can't remember the
> commercial products that do this off-hand). Google and you'll find a
> few research projects using GPS for attitude as well as
> heading. Cost is not on for gliders real soon. Compasses are very
> cranky beasts, especially if they need to be glider- pilot-proof
> (about which I could tell stories for hours). Making something that
> is low-cost, self-calibrating, immune to stupid installations -
> that's the hard bit.

Many of the Marine GPS units have a `compass' option to add a second
antena and give a heading.

But if you are going to add a second set of electronics, then it is
almost a done deal to add TWO sets and have the full 6D position and
orientation data.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

Derrick Steed

June 17th 04, 04:50 PM

Isn't there some form of flux gate compass which can be used? The GPS's we use originated in the maritime market (after NMEA is a maritime standard), surely there is a flux gate compass with NMEA output.

Rgds,

Derrick.

Andy Durbin

June 17th 04, 04:52 PM

"David Starer" > wrote in message >...
> The GPS gives TRACK, not HEADING. It can't tell what direction the glider is
> pointing in, only the direction its motion is taking it across the ground.
>
> David Starer

True, but the issue is confused because some Etrex models incude a
magnetic heading sensor.

Andy

Bill Daniels

June 17th 04, 04:59 PM

"Derrick Steed" > wrote in message
...
> Isn't there some form of flux gate compass which can be used? The GPS's we
use originated in the maritime market (after NMEA is a maritime standard),
surely there is a flux gate compass with NMEA output.
>
> Rgds,
>
> Derrick.
>
A flux gate compass is just another kind of magnetic compass. It eliminates
the jiggling of a pivoting compass card but it is still subject to
installation, variation and dip errors. The dip error means that it only
provides useful data when the wings are level. Still, they are probably
cheaper than GPS compasses.

GPS compasses are elegant in that they point to true north.

Bill Daniels

Chris OCallaghan

June 17th 04, 06:09 PM

Dave,

Posting to the group in hopes you answer might serve others...

My SN-10B serves me well. However, I am having a small problem based
on airspeed error. I have noted on ridge flights that after prolonged
high-speed flight without turns, the instrument starts counting up the
wind speed. On one leg, I saw a 25 knot increase. Clearly I need to
fix the asi error table, but if the SN-10 is counting up, which way do
I need to go in the table?

OC

Stephen Haley

June 18th 04, 12:14 AM

Marine users have been using electronic compasses for some time. These are
fluxgate compasses and most have NEMA output so what you want is not
impossible. The marine ones are expensive circa $400 but there are a new
bread of digital compasses some of which are included in GPS handhelds but I
cannot see if any have NEMA outputs. In addition there ae some aviation
sensors coming n the market (MEMS) (see
http://www.willow.co.uk/html/heading.html) You will need a NEMA sentance
output of HDM or better HDG from such a device and a NEMA concatenator to
meld the NEMA output into the IPAQ datastream.

On the Plus side
You would have a compass that had little lag - easier to roll out of
thermals onto heading
You would get your wind data

On the downside
Expensive as one-off
Yet more battery drain
Device would need A solid state memory for an electronic version of
deviation card
Device would have to be installed in tail as they are V sensitive
You only get Magnetic heading from device - GPS is essentially True and if
flying in areas of local magnetic anomalies you will get strange results.

Given most gliders fly Track as opposed to bearing it would be easier simply
to note magnetic heading & speed once on track and make sure that the two
remain constant if they diverge then your wind direction has changed and you
can either do the mental maths (or use a flight computer) or put in a 360.

What we are all really waiting for is a Touch Single panel display system
that would include something like this along with a Head-Up display. But the
market is just too small to make something like this a real economic
proposition at this time along with the associated battery drain. You would
be lucky to sell more than 500 units.

rgds
stephen

"Bill Daniels" > wrote in message
news:_y8Ac.53766$0y.15362@attbi_s03...
> Dave, can it give highly accurate, real-time wind data, second by second
on
> a straight one hour glide?
>
> My last flight showed this problem during a long glide. For 30 miles the
> wind data showed SW winds at 20 knots but then I noticed the glider
drifting
> to the west. Two 360 turns and the computer showed wind at 090 at 10
knots.
> When I crossed the wind shift line I had a chance to change strategy. 30
> miles later when the wind error became obvious it was too late.
>
> More and more I think we need very accurate real-time wind data with no
> requirement to be constantly changing heading. A cheap, reliable heading
> sensor would make this possible.
>
> Bill Daniels
>
> "Dave Nadler YO" > wrote in message
> m...
> > Bill - The heading is not required. In the ILEC SN10 we do this
> > without heading, and it normally has the wind by the time you're
> > off tow. Pilot feedback and measurements indicate that we do
> > it quite accurately. We just use TAS and GPS ground track over
> > multiple observations (TAS requiring accurate IAS, press, temp).
> > Best Regards, Dave "YO"
> >
> > "Bill Daniels" > wrote in message
> news:<gw%zc.59643$HG.25574@attbi_s53>...
> > > I've been analyzing the IGC files from my flights and comparing them
to
> > > others.
> > >
> > > Generally, in good conditions, I'm circling less than 25% of the time.
> > > Other, far better pilots than I, are circling less than 15% of the
time.
> > > This means that wind data that depends on the glider flying circles
gets
> way
> > > out of date during the long glides. OK, "S" turns can give the
computer
> a
> > > chance to compute wind if you remember to fly them but there are still
a
> lot
> > > of long, straight glides.
> > >
> > > To compute real-time wind data we need Groundspeed, Ground Track (any
> GPS
> > > gives these)True Airspeed (Some computers do this if they have OAT,
> Pressure
> > > Altitude and IAS) and accurate heading data. Heading data it the
tough
> nut
> > > to crack.
> > >
> > > So, how do we get Heading? One way might be to put a GPS antenna in
> each
> > > wing and look at the carrier phase difference. If the computer saw a
> > > constant track, it could assume the wings are level and determine a
> heading
> > > value. This heading value might update an aerospace quality MEMS
> heading
> > > gyro that would maintain a flow of heading data to the glide computer
> during
> > > times when the wings were banked.
> > >
> > > With good heading data we could get uninterrupted high quality wind
data
> > > regardless of the gliders' maneuvering or lack of it.
> > >
> > > OK, RAS gageteers, how about it?
> > >
> > > Bill Daniels
>

Dave Nadler YO

June 18th 04, 02:27 AM

Hi Chris - Clearly you need our compass option ;-)
Give a call over the weekend to discuss your issue,
and also to tell me where you've located such a long ridge,
Best Regards, Dave "YO"

(Chris OCallaghan) wrote in message >...
> Dave,
>
> Posting to the group in hopes you answer might serve others...
>
> My SN-10B serves me well. However, I am having a small problem based
> on airspeed error. I have noted on ridge flights that after prolonged
> high-speed flight without turns, the instrument starts counting up the
> wind speed. On one leg, I saw a 25 knot increase. Clearly I need to
> fix the asi error table, but if the SN-10 is counting up, which way do
> I need to go in the table?
>
> OC

uavscience at NOSPAMmsn dot com

June 19th 04, 05:56 PM

One thing that a lot of the UAV guys are doing, is to use a magnetic
heading sensor coupled with a MEMS gyro, or if more money is available,
a FOG. The magnetic sensor can be used to periodically determine heading
and to correct for signal drift from the gyro. For instance, the gyro
can be used as the primary source for heading info, while the magnetic
sensor is used during long, stable glides. Very similar to how the DG
and compass are used in power planes. Of course, the gyro would have to
be either mechanically gimbaled to remain parallel to the horizon, or,
alternatively, several gyros on different axes can be used together to
determine actual heading change, rather than yaw rate.

Using some basic Kalman filtering, it should be possible to get fairly
accurate (<5-8 degree) heading info. This will, of course, be magnetic
heading, and subject to the usual accuracy issues. However, it might be
possible to correct the data to true heading by loading a map of lines
of deviation and magnetic anomalies (which can also be fed into the
Kalman filter). Simply feed the wind component data from the GPS, the
raw heading info from the magnetic sensor, and the stabilized data from
the gyro into a Kalman filter, and pretty stable and accurate heading
data should be available.

Definitely do-able. Let's do it! :O)

BTW, check out www.rotomotion.com. These guys have several fairly cheap
AHRS', as well as several cheap IMU's. They've also published a bunch of
open source code on Sourceforge under the Autopilot project
<http://autopilot.sourceforge.net/> with an effective Kalman filter to
integrate GPS, IMU, and magnetic sensor data.

- Robert

Dave Houlton

June 23rd 04, 12:02 AM

Derrick Steed wrote:
> Isn't there some form of flux gate compass which can be used? The GPS's we use originated in the maritime market (after NMEA is a maritime standard), surely there is a flux gate compass with NMEA output.
>
> Rgds,
>
> Derrick.

Hi, Bill.

The Garmin eTrex Vista includes GPS, barometric altitude, and electronic
compass. IIRC all the above data are output on the serial interface as
NMEA or Garmin sentences.

Can you get by with +- 2 degrees heading accuracy? No idea how big the
dip error is when wings banked, but maybe your flight computer could be
smart enough to use the compass when straight & level and switch to
turning-base wind calculation when banked?

http://www.garmin.com/products/etrexVista/spec.html

Dave

Bill Daniels

June 23rd 04, 12:23 AM

"Dave Houlton" > wrote in message
...
> Derrick Steed wrote:
> > Isn't there some form of flux gate compass which can be used? The GPS's
we use originated in the maritime market (after NMEA is a maritime
standard), surely there is a flux gate compass with NMEA output.
> >
> > Rgds,
> >
> > Derrick.
>
> Hi, Bill.
>
> The Garmin eTrex Vista includes GPS, barometric altitude, and electronic
> compass. IIRC all the above data are output on the serial interface as
> NMEA or Garmin sentences.
>
> Can you get by with +- 2 degrees heading accuracy? No idea how big the
> dip error is when wings banked, but maybe your flight computer could be
> smart enough to use the compass when straight & level and switch to
> turning-base wind calculation when banked?
>
> http://www.garmin.com/products/etrexVista/spec.html
>
> Dave

The "compass" on many handheld GPS units really shows ground track although
I think some of them have electronic flux gate compasses. To compute true
wind data you need four inputs: True Heading, True Airspeed, Ground Speed
and Ground Track. We only need to add heading to get true wind info.

There are fluxgate and other magnetoresistive sensors that use the earth
magnetic field to determine heading. The $500 NMEA marine units would
probably work but they suffer from all the problems that any magnetic
compass has. There are other clever devices that detect the magnetic field
in three axes and, with the GPS position data and a look-up table, subtract
the variation and dip errors to output true north.

I still like the idea of a double-headed GPS receiver with two antennas a
meter apart on the fuselage centerline. These should be good to a half
degree accuracy. If you add MEMS gyros for a "coast through" in the event
of a GPS signal interruption, you have an elegant heading sensor.

Bill Daniels

Bill Daniels

June 23rd 04, 12:34 AM

Bill Daniels

June 23rd 04, 12:34 AM

Bill Daniels

June 23rd 04, 01:15 AM

I have no idea how three copies of the previous post got sent. I swear I
hit the send button only once.

Bill Daniels

tango4

June 23rd 04, 05:39 AM

JLR-10 GPS Compass
http://www.jrcamerica.com/product.asp?Product_Id=17778

Furuno SC-50
http://www.maritech.com/satellite_compass.htm

both around US$ 3500.

And we complain about the cost of loggers!

Ian

"Bill Daniels" > wrote in message
news:eb3Cc.94362$Sw.26496@attbi_s51...
>
> "Dave Houlton" > wrote in message
> ...
> > Derrick Steed wrote:
> > > Isn't there some form of flux gate compass which can be used? The
GPS's
> we use originated in the maritime market (after NMEA is a maritime
> standard), surely there is a flux gate compass with NMEA output.
> > >
> > > Rgds,
> > >
> > > Derrick.
> >
> > Hi, Bill.
> >
> > The Garmin eTrex Vista includes GPS, barometric altitude, and electronic
> > compass. IIRC all the above data are output on the serial interface as
> > NMEA or Garmin sentences.
> >
> > Can you get by with +- 2 degrees heading accuracy? No idea how big the
> > dip error is when wings banked, but maybe your flight computer could be
> > smart enough to use the compass when straight & level and switch to
> > turning-base wind calculation when banked?
> >
> > http://www.garmin.com/products/etrexVista/spec.html
> >
> > Dave
>
> The "compass" on many handheld GPS units really shows ground track
although
> I think some of them have electronic flux gate compasses. To compute true
> wind data you need four inputs: True Heading, True Airspeed, Ground Speed
> and Ground Track. We only need to add heading to get true wind info.
>
> There are fluxgate and other magnetoresistive sensors that use the earth
> magnetic field to determine heading. The $500 NMEA marine units would
> probably work but they suffer from all the problems that any magnetic
> compass has. There are other clever devices that detect the magnetic
field
> in three axes and, with the GPS position data and a look-up table,
subtract
> the variation and dip errors to output true north.
>
> I still like the idea of a double-headed GPS receiver with two antennas a
> meter apart on the fuselage centerline. These should be good to a half
> degree accuracy. If you add MEMS gyros for a "coast through" in the event
> of a GPS signal interruption, you have an elegant heading sensor.
>
> Bill Daniels
>