Wind estimation techniques.

[AussieShooter]

I have a kestrel wind gage and was wondering how shooters measure windage out in the field using only natural objects (grass, trees etc).

To what extent do shooters classify these objects such as light leaves and branches with so much movement will equal x and light leaves medium branches = y.

What methods are used to classify foliage types? I don't want to have to get out the kestrel every time before a shot over a long period of time.

 

[AussieShooter]

Re: Wind estimation techniques.

Anyone?????

 

[Lowlight]

Re: Wind estimation techniques.

There is a lot written on wind reading on here, and generally speaking all wind estimations starts from the shooter, as your experience grows you can move that skill downrange but looking at the "objects" down range is a good fall back but really a poor way to do it.

I did several classes with combat weatherman here in the States, who's job it is to follow around the spec ops guys to call the weather for a host of things. They excel at wind reading but do so with an array of instrustments to include balloons. I have seen a combat weatherman during a storm on the range outline a tornado and predict it's drop from miles away, to the point where 3 minutes after he said a funnel touched down exactly where he said. Every time they showed I would ask them about wind and objects, and the answer is always, to the man, "what is that wind doing 1000 yards away looking at the trees" and they say, "blowing" because you can't tell the speed it's a guess.

This said, here is a rule of thumb used by some, it's sort of old school, but can help,

0-1 mph wind imperceptible
no grass of leaf movement
smoke rises straight up

1-2 mph cooling effect of wind may be noticed
light movement of grasses
only a few leaves on any given tree in motion

3 mph wind pressure can be felt on bare arms
grasses obviously in motion
all leaves on any given tree in light motion

4 mph wind pressure can be felt on face
small twigs bearing leaf clusters begin light motion

5 mph tips of smaller branches begin motion that hold the leaf
limbs

6 mph the trunk branches start to move. These are the heavy
limbs holding the smaller branches

7 mph larger (trunk) limbs begin motion
younger (softer) leaves begin to flip over on the windy
side of the trees

8 mph tree tops are in light motion
mature leaves flip over on the windy side of trees

9 mph tree tops show obvious movement
almost all leaves flip over

10 mph wind pressure can be felt against the body
tree tops show substantial movement
mirage runs slowly and parallel to the ground

11 mph same as above

12 mph wind pressure can be felt against the body

12-15 mph dust is raised
lighter debris moves around
mirage blows off completely in exposed areas

15-20 mph dust clouds blow around
debris blows around
smaller tree trunks sway
major limbs on larger trees in constant motion

20 + mph difficult walking
large tree trunks sway

You have a kestrel, dope the wind at you, get a real reading, then look at the terrain and objects to decide whether to adjust that reading up or down based on what you see.

But all wind calls start at the shooter, this is the science department, everything else is Art and can be very subjective. Especially as you go beyond 8-10MPH, after that very few indicators will tell you much more than it is "blowing" and hard. Even Mirage will begin to just lay over only giving you direction as velocities above 10-12MPH sort of look the same to the untrained eye.

 

[gvanhyning]

Re: Wind estimation techniques.

I like Lowlight's response and made some notes for myself. Since you have a Kestrel, I would suggest you estimate the wind based on what you are seeing and feeling then get the meter out and measure. See how close you can get each time. With some practice over time you may not need the Kestrel.

 

[Ulakhan]

Re: Wind estimation techniques.

There is a 5 min youtube video that goes through the winds effect on vegetation in the 0,5 - 5 m/s bracket. I don't know how accurate this explanation is and I suspect Lowlights run-through is more detailed.
Hope it helps
Longrange Blog 5, Wind

 

[shooter.dm]

Re: Wind estimation techniques.

I saw that video it was preaty good information

 

[TOP PREDATOR]

Re: Wind estimation techniques.

search "beaufort wind scale"

from a shooting range at the shooting position, you can go by a rule of thumb (sorry about the caps, copied an pasted from elswhere). it works pretty decent for bullets or golf balls if your playing a course on a windy day:

STANDING UP STRAIGHT HOLD SOME BLADES OF GRASS, A 6" TO 8" STREAMER OF PAPER OR RIBBON, OR EVEN
A PINCH OF DIRT. HOLD YOUR ARM STRAIGHT OUT AT 90 DEGREES, LET GO, KEEP YOUR ARM STILL OUT. LET THE
OBJECT YOUR USING HIT THE GROUND THEN POINT TO IT. THE ANGLE OF YOUR ARM AS YOUR POINTING TO IT IS
THE KEY, AND IF YOUR NOT GOOD AT JUDGING ANGLES, YOU COULD USE THE COSINE - WIND ESTIMATING TOOL (or a simple protractor).

TAKE THE ANGLE, DIVIDE IT BY 4, AND YOU HAVE A WIND SPEED. SO IF YOUR HOLDING YOUR ARM OUT AND
LEAVE GO OF THE OBJECT, AND THE ANGLE YOUR POINTING AT IT IS 45 DEGREES (WHICH IS HALF WAY BETWEEN
YOUR OUTSTRETCHED ARM AND YOUR SIDE), YOU HAVE A 45 DEGREE ANGLE. IF THE OBJECT FALLS CLOSER,
SAY QUARTER OF THE DISTANCE, YOU ROUGHLY HAVE A 22 DEGREE ANGLE DIVIDE IT BY 4 = 5-6 MPH WIND.
BENCHREST SHOOTERS USE THIS PRINCIPLE BY OBSERVING WIND FLAGS PLACED AT DIFFERENT RANGES.
YOU CAN USE THIS METHOD TO SOME DEGREE OF ACCURACY BY LOOKING AT AN UPRIGHT TREE AND NOTING
HOW AND AT WHAT ANGLE A LEAF BLEW OFF. IMAGINE THE TRUNK OF THE TREE AS THE BOTTOM OF A "T",
TO GET YOUR 90 DEGREE GRAPH, AND NOTICE THE ANGLE OF THE FALLING LEAF; THE MATH IS THE SAME!
YOU COULD LOOK AT A PRETTY STRAIGHT UP PIECE OF GRASS AND DO THE SAME, BUT USE THE SWAY AS THE
ANGLE INDICATOR. YOU CAN DO THE SAME SITTING DOWN WITH YOUR TORSO UP, AND BEND AT THE ELBOW AS
YOUR CLOSER TO THE GROUND.

 

[AussieShooter]

Re: Wind estimation techniques.

Thanks for the very informative information. I will try and incorporate it in to my repertoire of shooting knowledge and skills.

 

[sniperaviator]

Re: Wind estimation techniques.

Since what I am interested in is the 90 degree crosswind component, can I just point my Kestrel 90 degrees to my line of fire and use that value as the crosswind component?

 

[Lowlight]

Re: Wind estimation techniques.

You point your kestrel to what ever direction the wind is coming from to get the wind speed, and then use that data as needed.

That is what the kestrel is for... that and training yourself to read the wind without the kestrel.

How else would you think of using it ?

 

[sniperaviator]

Re: Wind estimation techniques.

Well I know how to find the crosswind component based on the angle of wind to the line of fire, but if the Kestrel would be accurate at finding the 90 degree wind component DIRECTLY (when the wind is not blowing 90 degrees to the line of fire, day blowing 60 degrees to line of fire), by just pointing it 90 degrees to the wind, I could skip that step.

 

[Clark]

Re: Wind estimation techniques.

The wind is never perfectly pi/2 radians rotated from the line of fire.
I have been making two assumptions:
1) The bullet drift will be less than predicted in Quicktarget by multiplying by the cosine of how far from crosswise the wind is.
2) Just like the bullet, the Kestrel will read the same amount lower by holding the Kestrel pointed crosswise to the line of fire.

I could test the second one. I could measure the wind and then rotate pi/3 radians. I should read on half the other measurement.

OK, I just tried that. It does not work

The reading does not drop off to 1/2 until I rotate the Kestrel pi/2 radians.

More reason to hunt with a calculator.

At least I did something in mils. Maybe someday I will use one of my mil dot reticules for something.

 

[Bugaboo]

Re: Wind estimation techniques.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sniperaviator</div><div class="ubbcode-body">Well I know how to find the crosswind component based on the angle of wind to the line of fire, but if the Kestrel would be accurate at finding the 90 degree wind component DIRECTLY (when the wind is not blowing 90 degrees to the line of fire, day blowing 60 degrees to line of fire), by just pointing it 90 degrees to the wind, I could skip that step. </div></div>

I am not sure I understand exactly what you mean, but...
Kestrel calculates the Corosswind component this way: you point the Kestrel in the direction of the target and capture the integrated compass reading. Then, when you capture the wind velocity, Kestrel also reads the direction of the wind and calculates the Crosswind component. If you have the Horus ATrag, it will show you the windage directly.

 

[sniperaviator]

Re: Wind estimation techniques.

If you have a 10mph wind at 45 degrees to the line of fire, the force of that wind at 90 degrees to line of fire is .707 times the 10mph, or 7mph rounded.

If the vanes of the wind meter would properly capture the force of the wind at angles other than 90 degrees to the wind, you could turn the meter to 90 degrees to the line of fire (which would be 45 degrees to the wind) and the meter would read 7mph.

Not sure that is how the Kestrels work though.

Could be tested though

 

[louboyd]

Re: Wind estimation techniques.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bugaboo</div><div class="ubbcode-body">
I am not sure I understand exactly what you mean, but...
Kestrel calculates the Corosswind component this way: you point the Kestrel in the direction of the target and capture the integrated compass reading. Then, when you capture the wind velocity, Kestrel also reads the direction of the wind and calculates the Crosswind component. If you have the Horus ATrag, it will show you the windage directly.</div></div>

When taking a wind reading with the Kestrel (4500 series) always point the back of the kestrel into the wind. This captures the wind velocity and the wind azimuth. Crosswind and fore/aft winds are calculated based on the captured angles. Trying to hold the Kestrel at an angle with respect to the wind will at best cause confusion and will give wrong answers if using the Horus software. All angles in the Kestrel/Horus software are referenced to true north. Internally the Kestrel measures magnetic north but the magnetic declination is entered during the instrument setup. Read the instructions.

There are a lot of potential sources of error in using the Kestrel (or any local wind meter) to determine wind deflection of the bullet. Even if the wind is uniform over bullet's trajectory there is still the wind gradient. Wind increases in velocity vs height off the ground. Bullets don't fly flat even over flat ground, so the wind will be higher velocity relative to the ground over most of it's trajectory than the height of the rifle or target. The Kestrel/horus calculator does not take that into account. Nor should it since it's rare to have uniform wind even over dead flat ground. The Kestrel can only read the wind vector at one point where the shooter (or a spotter) takes the measurement. That may or may not have much relation to the wind over the bullet's trajectory. A kestrel meter IS NOT a substitute for skill at doping downrange wind.

The Kestrel is useful for comparing wind effect on local plants to measured local wind velocity. Using that knowledge is useful when observing similar plants downrange. Knowing how to dope winds varies a lot with terrain and available foliage.

The most accurate wind meter a shooter has available is the use of spotting shots though it may not always be possible to see bullet vapor trails or impacts, or be practical to take spotting shots.

 

[sniperaviator]

Re: Wind estimation techniques.

So what you are saying is the Kestrel is only calibrated to give correct wind speed when it is pointing directly at the wind.

 

[Lowlight]

Re: Wind estimation techniques.

if you start trying to "game" the wind you'll lose every time

 

[louboyd]

Re: Wind estimation techniques.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sniperaviator</div><div class="ubbcode-body">So what you are saying is the Kestrel is only calibrated to give correct wind speed when it is pointing directly at the wind.</div></div>

Yes, especially if you also want the correct azimuth. The compass will read the azimuth whatever direction you point it, but it will only calculate the wind velocity and it's azimuth correctly when it's back is pointed into the wind. If the meter has been set up according to the instructions, the readings will be relative to true north. That's what in Horus software in the Kestrel meter is expecting. I don't know if the Kestrel will give correct cosine of the velocity readings if it's tilted from the true wind direction, but nowhere in the instructions does it say to do that or mention the expected error if that's done. The only time you'd hold the Kestrel with it's back facing the target is to measure the "Dof" (direction of fire) or if the wind is blowing directly from the direction of the target.

 

[louboyd]

Re: Wind estimation techniques.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">if you start trying to "game" the wind you'll lose every time </div></div>

What does "game" the wind mean? I lead a sheltered life.

 

[kraigWY]

Re: Wind estimation techniques.

To me, Gameing the Wind means trying to second guess and compute for wind at differant ranges between you and the target using a wind meter at your firing point.

Maybe wrong, just a guess.

However, I don't see how it can be done. It's much simpler to just get a good estiment at mid range and go for it.

I'm not one for carrying machines and computers to the range. Simple data book (if done right) will cover that.

If you use MS Excell, and are interested PM me with your e-mail address and I'll send you an Excell Balistic Program. Put your data in, and it will give you a range chart (like you see in high power score books) for your data.

You can use paste this chart in your data book, estimate the mid range wind, and use the chart to make corrections based on your data.

Lot simplier and easier then fooling with wind machines and computers.

 

[Lowlight]

Re: Wind estimation techniques.

What I meant from gaming was the guy trying to take a short cut and hold the wind meter across the line of fire to read a "portion of the wind thinking that would work.

Gaming the system with the wind meter, instead of reading the actual wind velocity from the direction of origin.

 

[Clark]

Re: Wind estimation techniques.

Usually gaming a system means doing extra analysis, not less.

Louis Boyd is not sheltered. He has written about shooting in the wind for over 15 years.

 

[SLVGW360]

Re: Wind estimation techniques.

Yeah, one of the Best of the West guys advocated pointing your wind meter at your target while holding the display toward the shooter to get the cross wind component. I don't think that does anything but shield some of the wind with the frame of the unit. Sure it will likely show a lower number, but it's likely not measuring what he thinks.

 

[Clark]

Re: Wind estimation techniques.

I should not have had to test the kestrel to find out that it does not measure the wind vector in the direction the instrument faces.

The power in the wind is a function of the wind speed cubed, and could even go faster around some curved shape. And the prop spins freely with no load. If we tilted at solar cell off perpendicular, the current would drop off as the cosine of the angle. But it is not going to work with a wind meter.

I had a half baked thought that lived too long before this thread killed it. I guess I hoped it was true.

 

[Chanonry]

Re: Wind estimation techniques.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">What I meant from gaming was the guy trying to take a short cut and hold the wind meter across the line of fire to read a "portion of the wind thinking that would work.

Gaming the system with the wind meter, instead of reading the actual wind velocity from the direction of origin. </div></div>

The 4500 suggests that it is possible to do this with crosswind and headwind functions. I could never see how this could work with just a fixed impeller...

 

[louboyd]

Re: Wind estimation techniques.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> The 4500 suggests that it is possible to do this with crosswind and headwind functions. I could never see how this could work with just a fixed impeller...</div></div>

Where is that "suggested"? Your post made me curious so I emailed Kestrel's technical support and asked them if the off axis wind sensitivity varied with the cosine of the angle. I got this response:

"I'm afraid this is not a simple cosine function. From what I was told by a senior engineer a little over a year ago who was heavily involved with the impeller design (he retired last February), it is a significant deviation. However, no tests have been done to determine the magnitude of the wind as measured by the Kestrel in the range of parallel to the pivot axis of the impeller to perpendicular to that axis.

Our most recent test results indicate that there is no significant difference in the wind measurements regarding which side of the impeller the wind enters."

As to that last statement the magnitude would be right but the azimuth would be wrong by 180 degrees. What it also says though is that accurate wind measurements can only be made with the impeller aligned into the wind. The kestrel does not measure wind direction directly. It only measures the orientation of the body of the instrument when a reading referenced to true north derived from it magnetic compass.

 

[SaepeExertus]

Re: Wind estimation techniques.

Ever try using the mirage? Takes some practice to become proficent but I've found it to work great on sunny days. Also good for keeping you from breaking your position to look at trees if theres nothing in your sight picture to judge.

 

[Oneteam]

Re: Wind estimation techniques.

I agree, on sunny hot days, mirage can be read quite accurately once you have learned how.

 

[weberj62]

Re: Wind estimation techniques.

Have a range card that says the same thing that lowlight tposted so I second his post