Range Report Ballistic FTE/Kestrel

TonyC

TonyC

Sergeant
Full Member
Minuteman
Feb 19, 2008
210
12
England
#1
Can anyone clarify the use of Density Altitude as calculated by a Kestrel with Ballistic for iPod/iPhone?

Enable "Standardize Pressure" then input Density Altitude from the Kestrel in to the Altitude field ?

Other than saving on the amount of keystrokes is there a plus/minus to using Density Altitude vs. input of Baro Pressure (no station pressure option?), Altitude, Temp and Humidity.

Cheers

Tony




 
#2
Re: Ballistic FTE/Kestrel

If you have a Kestrel and the Ipod/Iphone in the field, you have no need for the concept of density altitude. Just put in the temperature, humidity, and pressure from the Kestrel in the appropriate place in the software.

Density altitude is useful for printing out a chart for your load which you take to the field to eliminate the need for a ballistic program.

If you want to know how to do that, see:

Making Ballistic Cards Using Density Altitude
 
#3
Re: Ballistic FTE/Kestrel

Lindy,

Maybe you can clarify for me a little further although I appreciate you may not have specifically used Ballistic (which I am running on an iPod so no automatic weather data)

I read from another article of yours that I should leave the altitude reference on the Kestrel at Zero to get Station rather than Baro pressure.

My assumption was that to use this data in Ballistic I would leave the altitude field at zero and input Station Pressure, Temperature and Humidity.

The input field on Ballistic is for Baro Pressure but if I'm leaving the altitude field at zero and input true Station pressure I'm good here right ?

I'm unclear on the "Standardize Pressure" option which greys out the ability to input Baro Pressure.

The guideline from Ballistic is as below but I am not familiar with JBM:-

"The "Standardize Pressure" switch instructs Ballistic to correct the pressure for the current altitude. This is the opposite of what JBM's "correct pressure" checkbox does, which tells JBM not to correct the pressure. "

Now I'm in circles on Baro, Station, corrected for altitude ....

I may just be tying myself in knots for no reason, (shit, I live on an Island with little in the way of real altitude that I am likely to shoot over) but I like to understand how stuff ticks and this is a new area for me.

TIA for any advice.

Tony

 
#4
Re: Ballistic FTE/Kestrel

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">My assumption was that to use this data in Ballistic I would leave the altitude field at zero and input Station Pressure, Temperature and Humidity.

The input field on Ballistic is for Baro Pressure but if I'm leaving the altitude field at zero and input true Station pressure I'm good here right ?</div></div>

I believe that's correct.

Here's another way to check that.

I'm currently at 8616 feet. The station pressure is 22.20 inches of mercury. The barometric pressure corrected to sea level is 29.89 inches.

Trying putting in an altitude of zero, with a pressure of 22.20 inches and that switch off, and them put in an altitude of 8616 with a pressure of 29.89 inches and the switch on, and see if you get the same program outputs.

If not, try reversing that switch. That should tell you which way is which.

Alternately, send me your iphone, and I'll figure it out...
laugh.gif

 
#6
Re: Ballistic FTE/Kestrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TonyC</div><div class="ubbcode-body">Other than saving on the amount of keystrokes is there a plus/minus to using Density Altitude vs. input of Baro Pressure (no station pressure option?), Altitude, Temp and Humidity.</div></div>

The Kestrel doesn't have to be calibrated to output density altitude.
 
#7
Re: Ballistic FTE/Kestrel

Density altitude allows me to create ballistic cards in advance. Doesn't matter what combination of factors are combined, as long as the end-result is a DA of 9k'.

In Sierra Bullets Infinity I'll input ICAO standard atmosphere for 9000' (pressure 21.28, temp 26.9), altitude of 0, humidity 0.
 
#8
Re: Ballistic FTE/Kestrel

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The Kestrel doesn't have to be calibrated to output density altitude.</div></div>

As long as you leave the reference altitude in the barometric pressure window of the Kestrel set to zero, it doesn't have to be calibrated to produce station pressure, temperature, and humidity, either.

The only advantage of using the concept of density altitude is that you can produce a density altitude dope table which can be used without a ballistic program as long as you have a way to compute density altitude.

 
#9
Re: Ballistic FTE/Kestrel

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What if you don't know your elevation ??</div></div>

I'm not familiar with the iphone software, but as long as you are putting in the station pressure, temperature, and humidity into the software, the elevation is irrelevant.
 
#10
Re: Ballistic FTE/Kestrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TonyC</div><div class="ubbcode-body">
The input field on Ballistic is for Baro Pressure but if I'm leaving the altitude field at zero and input true Station pressure I'm good here right ? </div></div>

Tony,

100% correct.

To 'work round' a program that is only set up to take a barometric input (to enable it to accept a station pressure input) just input station pressure and 'fudge' Alt to 0.

 
#11
Re: Ballistic FTE/Kestrel

Thanks Lindy, you are indeed Arcana Maven!

Mr Dog, sorry to hear you are not awash in Budvar at this point.

I'm trying to swing Wales for next week and I can pick your brain directly but unfortunately I may have to head to Canada.

Remember, no whisky......
sick.gif


TC



 
#12
Re: Ballistic FTE/Kestrel

When I use local BP (alitmeter setting), my Ballistic FTE program is dead on.

When I use the auto update for weather, the numbers arn't even close. Same goes if I manually input station pressure.

I usually just throw in 29.92, the temp, humidity, and altitude, then it's very close to my actual DOPE and my Nightforce program.
 
#13
Re: Ballistic FTE/Kestrel

A BP of 29.92 is the ICAO standard atmosphere sea-level barometric pressure.

Setting the software to always use that pressure, and correct it for the altitude you entered, is causing the program to ignore the fact that the local sea-level-equivalent barometric pressure may be very different from 29.92.

I cannot tell very much from the program author's web page, and I don't have the program to experiment with, but if you have a Kestrel, I suspect that you should manually enter the station pressure, temperature, and humidity, with the altitude set to zero and the Standardize Pressure button set to "off" to get the program to correctly calculate air density.

If you're going to use the auto update feature, the National Weather Service <span style="font-weight: bold">only</span> reports sea-level-equivalent barometric pressure, so you're going to need to enter the altitude, if it doesn't acquire that automatically, and turn Standardize Air Pressure "on", if I correctly understand the way the program works.

For more information on barometric pressure and ballistic software, see:

Barometric Pressure and Ballistic Software

The problem with programs which do some things automatically is that you may have trouble telling precisely what they are doing. If I were going to use that software, I'd contact the author to find out more information.

And if I compared that numbers that program puts out with JBM under the same conditions and got a substantial difference, I'd assume that the Iphone program was not working correctly.
 
#14
Re: Ballistic FTE/Kestrel

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What if you don't know your elevation ??</div></div>

I'm not familiar with the iphone software, but as long as you are putting in the station pressure, temperature, and humidity into the software, the elevation is irrelevant.
</div></div>

I use patagonia loadbase - - - if I dont have the elevation is it possible to get the station pressure with the kestrel 4500 ??? What if I am close - - most of my shooting is done between 900ft ASL and 1300ft. ???
 
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