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Advanced Marksmanship Terrain and Wind

Re: Terrain and Wind

You might want to try some specialized texts relating to parachute landing safety. Lots of different diagrams analyzing causes of turbulence and wind changes over and around trees and structures.

Some of the best long range demos at Bragg, Robinson, Benning, and Quantico have smoke pots set out at different yard lines showing how winds can be different on the same range.
 
Re: Terrain and Wind

Nice,

I like the idea of the parachute landing stuff

Did the smoke stuff, in more detail in the Online Training Lesson, but you can catch a piece of it here:

<iframe width="640" height="360" src="http://www.youtube.com/embed/i3YA2nQMTq4?hd=1" frameborder="0" allowfullscreen></iframe>

The area I was shooting was awesome for changes, cause & effect.
 
Re: Terrain and Wind

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I think you are gonna find I am pretty much the only one addressing it in a meaningful way.

Most shoot on flat ranges and look at wind as strictly linear.

They say, "X" MPH = Y Adjustments and not much more beyond that. </div></div>

Hey Frank,
You know exactly what I'm looking for from that comment.

I tried google, but found nothing helpful.

How is it covered in Sniper School?
 
Re: Terrain and Wind

RickP - in SW OR, the only areas I have available to shoot long are steep mountainous areas. A typical shot for me is across a narrow, steep draw.

Here are some thoughts:

- You can not read it in a book or watch it on a video - you actually have to go out there and sling lead. Formulas don't get it done, you really need to develop a sense for it.

Things that flatten the learning curve:

- Think of wind as water. If you look at a stream and watch the water flowing you will note that the effect of the current varies with the grade, depth, and the width of the stream bed (getting at the concept of recognizing what land formations lend themselves to velocity changes). Along the same line of thought, consider that if you send a volume of water down a 10" pipe, then step it down to an 8", then 6", then 4" and finally a 2" pipe - your increasing the pressure on that same volume of water with each reduction in pipe size. (Same thought if a wind flows up a broad valley and through a series of progressively more narrow formations.) Back to water - sometimes current flows over or around rocks, and sometimes it eddys or swirls back. If you watch that same riffle / rapid throughout a range of flow rates - you will notice that at some flow rates it merely flows over or around, while at other flow rates it eddys, and some times it not only eddys - it whirlpools. Same deal with land formations.

- Have a topo map (know how to read it and be able to recognize distinct land formations which are represented on the map with a quick scan - GPS Land Navigation by Ferguson has a section in the back which does a nice job of explaining this - if you need it).

- Understand seasonal prevailing wind patterns for the area - what direction are they generally coming from, what speed, how do things typically flow during the day, how does that change with the season or time of year?

- When you're on site, and thinking about the seasonal winds, reference the map and scan the area. Depending on the number and severity of topo changes in proximity to both the shooting position and the target location, you may want to start thinking about the cumulative effects on the wind at your target area that are generated by the topo formations that are 1, 2, maybe even 5 miles away.

- Watch for wind eddys - say your target is near the top of a draw, as the draw comes to it's vertical end, if it is steep it will have compounding effect on the wind speed. If the target is not on the crest and the wind speed is sufficient - you can see an eddy.

- Listen to the wind on site. If the weather is constant you will note that the wind is running more or less on a cycle. If you pay attention you can identify the change based on not just observable but audible conditions.

- About the only 'formula' work you can do (given the above already) is to take your spotter and use it to see if you can observe vegetation / foliage or mirage at each of the following locations - nearest any land formation that may have an impact on the wind at the target, 1/2 & 3/4s of the way to the target, the target itself. You can run the standard formulas based on these observations, but in time you will come to see that they belie the truth; and the truth is you really just need to be able to sense it, b/c there is as much art as there is science to it.




Good luck


 
Re: Terrain and Wind

Hey Mo,
Thanks that's good info.

You kind of touched on what I was looking for. Using the typical terrain features in a Topo (valley, saddle, depression, etc...)for how wind predominantly behaves around these features. I know it's not all standard but I think a diagram showing the terrain feature and how wind flows around them would be a good way show it.

One of the more important pieces of this that I'm looking for is turbulence. Sometimes shooting around a gully for example the wind is very unpredictable, forcing us to sometimes hold left then right. The other part I was looking for is when wind speeds up due to terrain features.

I think you made a good point, one need to shoot in these conditions to really get a handle on it. Unfortunately here in Florida the biggest terrain relief we have is the undulating sand at the beach. So as you can imagine, not very useful for learning to shoot in the wind.

BTW, your water analogy is good and helps picture things.
 
Re: Terrain and Wind

Concur that shooting experience and data building are going to help a whole lot more than trying to plug Bernoulli and Magnus numbers into calculations.

A good spotter with superior optics will be able to see the difference in wind speed and turbulence <span style="font-style: italic">in layers above the ground</span> and not just through the shooter's line-of-sight.
 
Re: Terrain and Wind

You have to shoot it or get someone with a spotter who can hopefully read the conditions, even then... wind is invisible how it acts is very dependent on the direction of travel at that given moment in time and space.

You can't just look at a map and "calculate" what you think will happen as small changes will effect that in several ways.

Wind happens and is the great equalizer, there is no short cut to saying "X" Terrain feature = "Y" Effects on your bullet.

Our experience when it comes to wind starts at our position and works its way out with experience, that experience is only achieved by actually shooting it under as many adverse conditions as possible which means "time & ammo" downrange.

Consider a Thunder Ranch HART class in the Fall, or getting into the ASC Match in WV for some conditions with Terrain. As far as fishtailing wind, that is a great example of unpredictability, you can't see the changes before they arrive and you can't depend on a spotter telling you while it happens. It's invisible and moves however it wants too at any given moment in time.
 
Re: Terrain and Wind

With terrain, think in terms of three dimensions and eddies downstream from obstacles.

Understand that local horizontal winds are driven by updrafts and downdrafts, and have their origins in solar heating. Different terrain's heat reflective values determine where thermals and downdrafts will originate. Air goes up in a column, cools and disperses outward in a fountain, then descends in a cylindrical form. Where it lands is a high pressure and density zone, and air from it is drawn across the terrain toward warmer thermals with their less dense (low pressure) air volumes that are evacuating upward as the thermal rises.

Another approach is to study streams and water flow in turbulent areas, like rapids and rocks. Some canoeing and Kayaking literature can be helpful here. It can help you visualize flow characteristics, and while they tend to be confined to two dimensions, and do not involve heat expansion and cooling contraction, they are a good initial lesson into turbulent airflow.

Before I got seriously into shooting, I had acquired several decades worth of experience with whitewater canoeing, and free flight model aviation, each of which are heavily dependent on being able to read the telltales of nature's air and water flows.

For example, hawks and other soaring birds will sometimes find the thermals for you (As they cross the invisible boundary into the thermal, they often experience a tipping motion of their wings, and deliberately turn into the thermal proper.), and the ground winds will usually flow toward the thermals.

Big river rocks initiate upstream flowing eddies just downstream from their location, and you can park your canoe in them and take a break while wild rapids flow nearby on either side.

Over time, an instinctive knowledge accumulates.

Until then, try setting up lots of wind ribbons at various distances alongside both sides of the trajectory and studying them in conjunction with their effects on bullet flight. Mine are 3-4 feet of surveyors' tape attached atop poles of roughly that same height. I drill the bottom ends and insert LOOOONNNG nails with their heads cut off, point down, which get pushed into the ground. Any wind that will blow them over is too powerful to learn anything useful from, anyway.

To make this work, you must avoid making any deliberate corrections for environmental conditions. With a goodly number of wind ribbons, you have something concrete to compare against the observable effects on POI. Good record keeping that combines ribbon directions with POI shifts will help here. It's going to take some time and work to develop reliable understanding, and nobody gets it perfect. The next step is to learn to observe and corellate the natural signs with the ribbons.

Until you can see and undestand the effects, any attempts at compensation are no better than scientific wild-assed guesses.

Afterward, they are still scientific wild-assed guesses, but they are better ones.

Greg
 
Re: Terrain and Wind

Not an advanced marksman by any means, but I am an advanced burner to a degree.

There are some good informative pieces out there on how terrain plays a role in wind from a fire control prespective. Much of it will not pertain as fire creates its own wind, but going through training we learn a lot about terrain and other obstacles and how they can affect wind currents, speed and drafts.

If I can put my hands on some of my old books I will.

Also, just noticed I missed the fire read above.
 
Re: Terrain and Wind

It won't give you formulas for shooting but aviation weather forecasting texts have lots of info on terrain features effects on wind in general and at certain times of day. Expensive books though, and you're only using a very small part of it, that's only marginally applicable.
 
Re: Terrain and Wind

Rick,

We ran a course last year on Stickledown, Bisley ( a range renowned for its difficult terrain/wind) for spotters and shooters. Specifically to assist shooters to read the wind conditions on difficult ranges and geared toward both sport and professional end users. The notes from this course are avilable if you PM me.

Hope this helps?