Circling for rodents?

In article 40ee83d7@
Bird fight is not like our flight where what we're doing is totally
alien and has to be (mostly) a conscious process. Birds fly quite
UNconsciously. What they see is "integrated" with what they feel in
their muscles. There is no separate process for "I am entering a
thermal" which is different from "I am in a steady climb". It's all one.

They measure altitude with their eyes as Bill Daniels said. They
'recalibrate' their gyros continuously by looking around. They're not
much better at raw data IMC than we are and lose their 'calibration'
quite quickly in cloud.

Are you sure about this? I have seen birds flying in cloud quite
successfully.

Many of the ideas are interesting but I'm with Occam's Razor. Birds fly
like we walk - by looking around to 'calibrate' the inner ear balance
mechanism and feedback from muscles. I can't see a real need for any
other unique mechanism.

... until we get to intercontinental migration.

GC


--
Mike Lindsay

Graeme Cant wrote:

Robert Ehrlich wrote:
Mike Lindsay wrote:
...
Presumably by integrating all the information it's getting from muscle
tension in wing muscles, airspeed from pressure on feathers, and sense
organs in the lining of bone cavities?


No, integration can't work in the long term because of the
accumulation of errors along time.

No Robert. I didn't mean 'integration' and I don't think Mike meant
'integration'. We meant integration.

Our integration is not the mathematical opposite of differentiation.
We're simply saying it takes data from all its information sources to
decide what's happening. It doesn't look at each one separately like we
shift from ASI to horizon to vario to altimeter to compass picking up
separate bits of information. With a bird it's all one. It's integrated.

This is how inertial navigation
systems work, but the integration process is carried with a precision
that no brain can meet, and they need absolute attitude information
from gyros, and nevertheless need recalibration after some time. I
think without the gyros, i.e. obtaining attitude also by integration
of rotational accelerations, the precision would be lost after a few
minutes.

Bird fight is not like our flight where what we're doing is totally
alien and has to be (mostly) a conscious process. Birds fly quite
UNconsciously. What they see is "integrated" with what they feel in
their muscles. There is no separate process for "I am entering a
thermal" which is different from "I am in a steady climb". It's all one.

They measure altitude with their eyes as Bill Daniels said. They
'recalibrate' their gyros continuously by looking around. They're not
much better at raw data IMC than we are and lose their 'calibration'
quite quickly in cloud.

Many of the ideas are interesting but I'm with Occam's Razor. Birds fly
like we walk - by looking around to 'calibrate' the inner ear balance
mechanism and feedback from muscles. I can't see a real need for any
other unique mechanism.

... until we get to intercontinental migration.

GC

OK, you may call as you like the process of determining climb rate from
acceleration or muscle tension or any other differential information,
it will nevertheless be a mathematical integration, or an equivalent
process, but as the result is unique starting from a known state, any
equivalent process is the same process.

None of the mechanism mentionned in the previous post (acceleration,
muscle tension, ground watching), except the use of a pressure sensor,
can explain how birds feel they are climbing, and as a matter of fact
someone said in a previous post that the evidence of such a sensor
in the birds has been proved and also that loosing this specific
information makes them unable to climb.

Martin Gregorie wrote:

On Thu, 08 Jul 2004 17:37:11 +0000, Robert Ehrlich
wrote:

A raised tail (or elevator) doesn't mean there is a down force on it.

I didn't say "a raised elevator". I was talking about a tail surface
that is tilted laterally in relation to the wing and said "a raised
tip" to describe the direction of tail tilt. Please do me the courtesy
of reading what I wrote before sounding off about it.


I read what you wrote and my remark was not about the "raised tip"
or the tilt, but about "so you can tell that they fly like we do
with down force on the tail". Sorry if you misunderstood me, or
if I misunderstood you, remember English is not my native language.

Bill Daniels wrote:

C'mon, now. Binocular depth perception ends for humans at about 20 feet and
is only really useful up to arms length, yet we can still judge distance
well. Since the bird is moving, they can use dynamic field depth perception
that has nothing to do with interocular distance.

Close one eye and move your head back and forth or up and down. You will
see what I mean. Birds and other small animals are observed to move their
heads constantly to better judge distances.

Ever ride one of those glass elevators (lifts) on the outside of a tall
building? Did you notice how powerful the impression of climbing is?

I still claim that they can see themselves rise away from the ground.
Excellent vision and the experience to use it to the fullest is the likely
explanation. It's the simplest explanation and requires no internal vario.


I can't believe that, except for very low heights. The elevator experience
you mention mention is for such heights, or at least when something (the
building itself) is very near.

The best processing system (e.g. the bird's brain) cannot infer anything
from missing or non significative input. In the case of climbing, the only
information on which you say they rely is the change in the apparent size
of ground features. I didn't do the computation, but I bet that the change
during one full turn is below the optical resolution of a bird's eye. In
this domain, we are better equiped than they are, our eyes are larger.
Nevertheless we can't decide if a glider or a bird is climbing when watching
them from below just by watching the change of their size during a short
time, except when they are very low. However I agree that after watching
a bird for a long time, as it changed from a beautiful thing with discernable
separate feathers at the tips to a vanishing little point in the sky, I can
say that it was climbing.

WinPilot and Mobile SeeYou already do this to a very
great extent by plotting out the flight path with climb
rate indicated on the moving map display. I have used
this to return to thermals going in and out of turnpoints
to good effect. They are not fast enough to really
be helpful in coring except over many turns, and even
then it's hard to stay oriented between the glider,
the display and the ground reference. WP Pro also has
a 'climb optimizer' that assumes your are flying in
a more-or-less circular path - it works pretty well
in my experience and can help the pilot divert attention
to other tasks while climbing.

I'm not sure you really need the strain guages to do
this as you already can measure rate of climb directly,
either through differential altitude readings from
the GPS, or more precisely through the TE pressure
system. I believe the CAI 302 also has an accelerometer
built in, so if you want to use acceleration you can
get it directly rather than having to derive it from
wing strain.

9B

At 14:48 09 July 2004, Ventus45 wrote:
And so could we, if we installed strain gauges along
the spars, say at 5
foot intervals, and connected them up to a minicomputer
which read them, add
an accelerometer, a standard netto vario setup, a gps,
and some fancy
software, and we should be able to create a computer
display that will be
able to produce a PPI 'map' display of a thermal as
we turn, gradually
building up the data, plotting 'lift' like contour
lines on a map, so we
could soon see where the 'core' was, and centre accordingly.
A good
research/thesis project for some bright spark at university.
Any takers ?

On Fri, 09 Jul 2004 17:10:49 +0000, Robert Ehrlich
wrote:

Martin Gregorie wrote:

On Thu, 08 Jul 2004 17:37:11 +0000, Robert Ehrlich
wrote:

A raised tail (or elevator) doesn't mean there is a down force on it.

I didn't say "a raised elevator". I was talking about a tail surface
that is tilted laterally in relation to the wing and said "a raised
tip" to describe the direction of tail tilt. Please do me the courtesy
of reading what I wrote before sounding off about it.


I read what you wrote and my remark was not about the "raised tip"
or the tilt, but about "so you can tell that they fly like we do
with down force on the tail". Sorry if you misunderstood me, or
if I misunderstood you, remember English is not my native language.

Fair enough and I was forgetting the native language difference.

We agree too on gliders minimising down-force, but it is still there -
otherwise the folks who've flown and survived with the tail bolt
missing (much earlier thread this year) would be unlikely to have
survived the experience with an intact glider, but I digress.

I was meaning to point out two things: (1) you can deduce the flight
load on a bird's tail by watching how it uses tail tilt to control a
turn and (2) the kite family have down-force on their tail and a fair
amount of it or the tilt would be ineffective.

I'd like to hear about similar observations of other species for
comparative purposes.



--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

In article , Robert Ehrlich
I can't believe that, except for very low heights. The elevator experience
you mention mention is for such heights, or at least when something (the
building itself) is very near.

The best processing system (e.g. the bird's brain) cannot infer anything
from missing or non significative input. In the case of climbing, the only
information on which you say they rely is the change in the apparent size
of ground features. I didn't do the computation, but I bet that the change
during one full turn is below the optical resolution of a bird's eye. In
this domain, we are better equiped than they are, our eyes are larger.

On the other hand, do you think you'd be able to spot a mouse from
3000ft? No problem for some birds of prey.
--
Mike Lindsay

In article , Robert Ehrlich
I can't believe that, except for very low heights. The elevator
experience
you mention mention is for such heights, or at least when something (the
building itself) is very near.

The best processing system (e.g. the bird's brain) cannot infer anything
from missing or non significative input. In the case of climbing, the
only
information on which you say they rely is the change in the apparent size
of ground features. I didn't do the computation, but I bet that the
change
during one full turn is below the optical resolution of a bird's eye. In
this domain, we are better equiped than they are, our eyes are larger.


You don't look down to see height changes, you look out at an angle. You're
not looking for changes in the size of objects, you look for changes in
angles. It's just like we judge height on final approach to landing. I can
judge the strength of thermals visually up to 1000 meters or so and I bet
the birds can do a lot better.

Bill Daniels

??Back in my hang gliding days I participated in a competition at ?Grandfather Mountain in North Carolina - about an 800 foot cliff ?followed by another 800 feet of mountain Ð and the cliff was part of a ?soarable ridge. Grandfather mountain is a tourist attraction with a road ?to the top and a gift shop at the summit. We knew we weren't going to ?soar that day because we had trouble walking into the gift shop. The ?weather station inside was reporting winds in excess of 90 mph. But the ?wind direction was perfect - dead on the ridge.??We didn't soar that day but the local residents did. They have ravens at ?Grandfather mountain - lots of ravens. We were literally hanging on to ?any thing we could because we were afraid of being blown off the ?mountain. And, walking across that suspension bridge between the 2 peaks ?was probably not the smartest move. Anyway, the ravens were soaring the ?flippin' ridge. They had their wings tucked in real close and were just ?zipping along. T
hey were at ridge top level about 30 feet in front of us ?and it was just amazing. I can only guess at what their airspeed was, ?but they were probably moving across the ridge at 20 to 30mph and so ?when you factor in the 90+ mph wind speed, their ASIs were probably ?hitting near 130. You'll never convince me they were flying to catch ?lunch - they were flying because they were having a blast. Of this I ?have absolutely no doubt.??Tony V. LS6-b "6N"?

Bill Daniels wrote:

You don't look down to see height changes, you look out at an angle. You're
not looking for changes in the size of objects, you look for changes in
angles. It's just like we judge height on final approach to landing. I can
judge the strength of thermals visually up to 1000 meters or so and I bet
the birds can do a lot better.

Bill Daniels

Well, the changes in (apparent) size of objets is nothing else than a change
in an angle. I agree that looking for such an angle just below the glider is
not what will maximize the change for a given height change. If your method
is by watching the change in the angle of the directions of some fixed ground
feature and the horizon, it can easily be shown that the maximum rate of change
is obtained by looking at some feature at 45 degrees below the horizon. In this
case, the change rate, in radians per climbing meter, is 1/(2*height), at 1000
meters the rate of change is of 1.7 minute per meter, in order to see a 1
degree change when climbing at 2 m/s, you have to wait 35 seconds.
Difficult but workable. I should try it in my next flight, although I think I
will not be able to perceive changes below 10 degrees, when looking at 45 degrees.
Looking toward a more horizontal direction should provide better senitivity, as
the fixed feature and the horizon are together in the visual field, but the
rate of change of the angle is much lower. When looking in the same direction
as on final approach, i.e. the direction of the 1/10 slope, the rate of change
is 1/(10*height) radians per climbing meter, 5 times lower than at 45 degrees,
you have to wait nearly 3 minutes climbing at 2 m/s to see a 1 degree change
at 1000 m.