Wind speed calculator

[Christopher Rance]

I was reading the Field Firing Solutions manual and on page 55, it goes into discussion on the wind vector screen and the wind calculator function. The example used is;

Example: Say at 950 yards is some burning rubble and the smoke is moving from left to right across his field of view. The shooter starts the timer as the smoke crosses the far left edge of his reticle and when the smoke crosses the far right edge of the reticle he stops the timer. The shooter knows that the entire horizontal element is 10 mils wide. When he stops the timer, 1.9 seconds have elapsed and the calculator declares that the smoke is traveling at 3 mph. That value matches the wind speed he measured at his shooting location so he is confident 3 mph is a good value to use over his course of fire.

I'm trying to figure out how to do the math for the example above? Using my AB Kestrel and the speed estimate calculator, I input;
Range: 950 yd
Mvmt: 10.0 Mil
Time: 1.9 sec

but it gives me a speed estimate of 10.2 mph.

Is there a variable that I'm missing? Reason for me asking is, I'm trying to find a way to make this into a formula similar to what we teach at our schoolhouse, i.e. like our moving target formula; Target covers X mils in (1 second) x TOF = MIL hold

Any help is appreciated or maybe I'm just going down a rabbits hole here haha.

 

[Deleted member 113831]

I was reading the Field Firing Solutions manual and on page 55, it goes into discussion on the wind vector screen and the wind calculator function. The example used is;

Example: Say at 950 yards is some burning rubble and the smoke is moving from left to right across his field of view. The shooter starts the timer as the smoke crosses the far left edge of his reticle and when the smoke crosses the far right edge of the reticle he stops the timer. The shooter knows that the entire horizontal element is 10 mils wide. When he stops the timer, 1.9 seconds have elapsed and the calculator declares that the smoke is traveling at 3 mph. That value matches the wind speed he measured at his shooting location so he is confident 3 mph is a good value to use over his course of fire.

I'm trying to figure out how to do the math for the example above? Using my AB Kestrel and the speed estimate calculator, I input;
Range: 950 yd
Mvmt: 10.0 Mil
Time: 1.9 sec

but it gives me a speed estimate of 10.2 mph.

Is there a variable that I'm missing? Reason for me asking is, I'm trying to find a way to make this into a formula similar to what we teach at our schoolhouse, i.e. like our moving target formula; Target covers X mils in (1 second) x TOF = MIL hold

Any help is appreciated or maybe I'm just going down a rabbits hole here haha.

You forgot to divide the 10 mils by 1.9 sec.

10 mils / 1.9 sec = 5.2 mils per sec. That is the average mils per second.

Multiply the 5.2 mils per sec. by the TOF (5.2 x TOF as per your formula) to arrive at your hold.

 

[pbatesaz]

You forgot to divide the 10 mils by 1.9 sec.

10 mils / 1.9 sec = 5.2 mils per sec. That is the average mils per second.

Multiply the 5.2 mils per sec. by the TOF (5.2 x TOF as per your formula) to arrive at your hold.

The hold calculated per Skookum is correct, however, the 3mph wind estimate is incorrect. It should be the 10.2 mph.... or I am down the same rabbit hole.

 

[Diver160651]

You forgot to divide the 10 mils by 1.9 sec.

10 mils / 1.9 sec = 5.2 mils per sec. That is the average mils per second.

Multiply the 5.2 mils per sec. by the TOF (5.2 x TOF as per your formula) to arrive at your hold.

That’s for moving targets and takes angle and mph out of the mix.

I think he is asking to use the reticle to determin the MPH speed vrs the hold solution

 

[Deleted member 113831]

That’s for moving targets and takes angle and mph out of the mix.

I think he is asking to use the reticle to determin the MPH speed vrs the hold solution

You are correct, I totally missed what he was asking for.

Doing the math the hard way, I too arrived at a wind speed of 10.2 mph.

 

[Diver160651]

You are correct, I totally missed what he was asking for.

I think he wants something like
((Range Meters x .001) x mils per sec))x2.237

The issue with this is that angles totally screw it up - we are just better using tradition wind ques..

Using a similar mover formula for moving objects that takes angle out of play, just does not work well for wind where the angle is important.

 

[Deleted member 113831]

I think he wants something like
((Range Meters x .001) x mils per sec))x2.237

The issue with this is that angles totally screw it up - we are just better using tradition wind ques..

Using a similar mover formula for moving objects that takes angle out of play, just does not work well for wind where the angle is important.

Ha! you were smart enough to derive the constant. I did it the 5th grade math way.

 

[Deleted member 113831]

I think I figured it out for yards:

Range (yards) / 1000 x (mils per sec) x 2.04 (constant) = MPH

 

[Diver160651]

I think I figured it out for yards:

Range (yards) / 1000 x (mils per sec) x 2.04 (constant) = MPH

That’s shorter for sure, because you don’t have to work natively in meters, or use a constant (or a super rough 10% of the yardage for head math)..

But at the end of the day, we’d then still really need Trig to deal with the angle of movement.

By the time we’d figure it out the wind, it is not really the same or our target would have walked away anyway.

 

[Deleted member 113831]

That’s shorter for sure, because you don’t have to work natively in meters, or use a constant (or a super rough 10% of the yardage for head math)..

But at the end of the day, we’d then still really need Trig to deal with the angle of movement.

By the time we’d figure it out the wind, it is not really the same or our target would have walked away anyway.

I get what you are saying, but the OP is a sniper. They can spend a lot of time in a hide and this work is meant to be done well ahead of taking a shot. It is just one more way to confirm and cross check what you are seeing from other indicators.

 

[Diver160651]

yep, but the reason they don't include 2.237 as a major part of the spinup, is because it doesn't work better/faster than the other methods

 

[Christopher Rance]

Thanks guys for the responses. Yeah, I just was reading through their manual and I thought the example used was interesting, as smoke is a common indicator in urban areas, and if the above formula provides another clue to what the wind is doing in that area, I'm alright with that. Again, I appreciate your guys help. It's always cool to see how the math works out.

 

[Deleted member 113831]

Thanks guys for the responses. Yeah, I just was reading through their manual and I thought the example used was interesting, as smoke is a common indicator in urban areas, and if the above formula provides another clue to what the wind is doing in that area, I'm alright with that. Again, I appreciate your guys help. It's always cool to see how the math works out.

So, to reiterate just a bit....2.04 is the constant for yards, and Diver's 2.237 is the constant for meters.

And the example in the FFS manual is a typo if it says 3mph.

 

[Christopher Rance]

So, just to reiterate just a bit....2.04 is the constant for yards, and Diver's 2.237 is the constant for meters.

And the example in the FFS manual is a typo if it says 3mph.

I appreciate that. I'll test it out on our range with some burn barrels. See what I can get from it and if its something we can use.

 

[_Windrider_]

I love FFS but sometimes he makes it way too complicated.

 

[Diver160651]

I appreciate that. I'll test it out on our range with some burn barrels. See what I can get from it and if its something we can use.

I was communicating with Blaine he is getting the same 10.23.. using FFS or the math

Am I reading the thread wrong? Are you just reading the manual as an example or using FFS and getting weird output?

 

[Christopher Rance]

I was communicating with Blaine he is getting the same 10.23.. using FFS or the math

Am I reading the thread wrong? Are you just reading the manual as an example or using FFS and getting weird output?

No just reading the manual. The example must be a typo then. That what was confusing me, as the example and the solution wasn't adding up, and I wanted to figure out the math behind it and see if we could do it without the software.

 

[Diver160651]

No just reading the manual. The example must be a typo then. That what was confusing me, as the example and the solution wasn't adding up, and I wanted to figure out the math behind it and see if we could do it without the software.

Oh, sorry that makes sence. I thought your program was spacing

 

[Diver160651]

Oh, sorry that makes sence. I thought your program was spacing

Blaine made the change to the manual— thanks