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density altitude

 
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  #1  
Old 01-04-2011, 08:27 PM
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density altitude

Is anyone using density altitude cards for there come ups as a backup to their electronics and PDA?
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  #2  
Old 05-09-2013, 06:16 PM
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Location: Aussie in Italy
Posts: 276
Re: density altitude

Hey Trueblue, density altitude is possibly the single most important factor in exterior ballistics predictions. However unfortunately outside of aviation circles it is not widely known or understood, nor is it used by software, making it essentially pointless.

DA gives us the effective resistance of the air on the bullet given the temperature, atmospheric pressure, altitude and humidity. Most programs must combine these factors if you enter them in, and make something similar to a DA calculation, but as a stand alone factor it could be viable replacement for the weather based variables we input.

By all means, use a Kestrel 4000 and log DA when shooting and you will be able to determine how your load performs in different places at different times of year, at different altitudes and temperatures with more accurately than by temperature and altitude alone.
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  #3  
Old 05-09-2013, 10:34 PM
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Join Date: Feb 2013
Location: Central MT
Posts: 691
Re: density altitude

"300 RUM, DA3000, 10MPH"

0400 -0002.2 -001.5 0700 -0010.0 -002.8 L1
0410 -0002.5 -001.5 0710 -0010.3 -002.8 L1
0420 -0002.7 -001.6 0720 -0010.6 -002.9 L1
0430 -0002.9 -001.6 0730 -0010.8 -002.9 L1
0440 -0003.2 -001.7 0740 -0011.1 -003.0 L1
0450 -0003.4 -001.7 0750 -0011.4 -003.0 L1
0460 -0003.6 -001.7 0760 -0011.7 -003.1 L1
0470 -0003.9 -001.8 0770 -0012.0 -003.1 L1
0480 -0004.1 -001.8 0780 -0012.3 -003.2 L1
0490 -0004.4 -001.9 0790 -0012.6 -003.2 L1
0500 -0004.6 -001.9 0800 -0012.9 -003.3 L1
0510 -0004.9 -001.9 0810 -0013.2 -003.3 L1
0520 -0005.1 -002.0 0820 -0013.6 -003.4 L1
0530 -0005.4 -002.0 0830 -0013.9 -003.4 L1
0540 -0005.6 -002.1 0840 -0014.2 -003.5 L1
0550 -0005.9 -002.1 L1 0850 -0014.5 -003.5 L2
0560 -0006.2 -002.2 L1 0860 -0014.8 -003.6 L2
0570 -0006.4 -002.2 L1 0870 -0015.1 -003.6 L2
0580 -0006.7 -002.2 L1 0880 -0015.5 -003.7 L2
0590 -0006.9 -002.3 L1 0890 -0015.8 -003.7 L2
0600 -0007.2 -002.3 L1 0900 -0016.1 -003.8 L2
0610 -0007.5 -002.4 L1 0910 -0016.4 -003.8 L2
0620 -0007.7 -002.4 L1 0920 -0016.8 -003.9 L2
0630 -0008.0 -002.5 L1 0930 -0017.1 -003.9 L2
0640 -0008.3 -002.5 L1 0940 -0017.4 -004.0 L2
0650 -0008.6 -002.6 L1 0950 -0017.8 -004.0 L2
0660 -0008.8 -002.6 L1 0960 -0018.1 -004.1 L2
0670 -0009.1 -002.6 L1 0970 -0018.5 -004.1 L2
0680 -0009.4 -002.7 L1 0980 -0018.8 -004.2 L2
0690 -0009.7 -002.7 L1 0990 -0019.2 -004.2 L2
1000 -0019.5 -004.3 L2

Yes I do and here is an example. My ballistics engine allows for an input for density altitude to correspond to a specific air density. I use the Kestrel 4000 to compute density altitude. DA is easy to use and only requires one input unlike many ballistics engines that require input of baro pressure, altitude, temp and humidity. Both methods produce the same results however only the DA method requires one input.
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  #4  
Old 05-10-2013, 01:36 AM
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Location: Aussie in Italy
Posts: 276
Re: density altitude

Good news, so what is the software you use?
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  #5  
Old 05-10-2013, 06:20 AM
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Join Date: Mar 2004
Location: Las Vegas, NV
Posts: 550
Re: density altitude

I use DA. The "Shooter" app for Android uses DA as one of the inputs for calculating its solutions.

Jeffvn
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  #6  
Old 05-10-2013, 06:35 AM
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Join Date: Jan 2005
Location: OK
Posts: 2,145
Re: density altitude

Jim, yes I print out a set of cards that range about 3000' in DA above and below the actual elevation I will be shooting at. I then confirm DA during the day with a Kestral. If you shoot an area often enough and your kestral goes down, you should have gleaned enough local knowledge to swag out a pretty good estimate of the DA based on past experience.
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