atmospheric inputs..specifically elevation

stvnbrg

stvnbrg

Member
Rating - 100%
9   0   0
Location
Edmonton, Ab
first off, what are you guys using for atmospheric inputs? are you using density altitude? corrected pressure? or manually inputting for station pressure and altitude? right now im using a corrected pressure which is accurate for sure, but using DA just seems easier. any thoughts or feed back? which ties in with my second question.

In regards to elevation, what are you calibrating your devices to? My GPS and also my Kestrel need to be calibrated, so I cant really calibrate them from each other! Taking the elevation off of a weather app from the nearest weather station does not seem nearly accurate enough.any insight?
 
ya the thing is i shoot in a wide variety of locations. Just want something a little more concrete to calibrate to.

Seems like the majority of shooters use DA
 
And a caution that you'll still get daily pressure variations. Set for your nominal density altitude based on elevation and expected average temperature, then deal with minor variations after that. Short range (say inside of 600m) won't see a significant change from the nominal for normal shooting days (rounded numbers here due to bullet BC etc. - in 308 and going from 4800' ASL to 200' ASL is a +3 MOA change, going 4800' ASL to 6800' ASL is a -2 MOA change - local variations in pressure are in the order of 0.25-0.50 MOA). If you're experiencing severe changes in atmospheric pressure, it's time to hide indoors.
 
Ya I think I hear what your saying. I'm not looking for set it and forget it inputs, I shoot with game time inputs. The real time atmospherics. Basically just wondering who does or doesn't use DA and why? And if so, how are you getting a reliable altitude when your kestrel and gsp both need to be calibrated with something?
 
I use density altitude, but when I had used the rest of the inputs (baro, temp, etc) I would use station pressure with the altitude set to 0. It's way easier than banking on google earth, gps barometric altimeters, or other means.

DA is easiest, but using station pressure with a 0 altitude is a close second.
 
chrisward3 said:
I use density altitude, but when I had used the rest of the inputs (baro, temp, etc) I would use station pressure with the altitude set to 0. It's way easier than banking on google earth, gps barometric altimeters, or other means.

DA is easiest, but using station pressure with a 0 altitude is a close second.
Click to expand...

And humidity...

DA is great if you have an app that uses it and the gear to get it.

While it's no doubt the best, learning the basics isn't a bad thing either!
 
stvnbrg said:
Ya I think I hear what your saying. I'm not looking for set it and forget it inputs, I shoot with game time inputs. The real time atmospherics. Basically just wondering who does or doesn't use DA and why? And if so, how are you getting a reliable altitude when your kestrel and gsp both need to be calibrated with something?
Click to expand...

Likely those not using it (like myself) is because they don't have the gear to get it. I have Kestrel but it doesn't provide DA, nor humidity (because it's pretty minor and saved me approx $200 on the kestrel.)

If you have it, use it. It's simple, fast, etc.

I still suggest everybody know HOW DA is determined and what's involved with it. Always good to understand.
 
Are you able to get an accurate temperature, pressure and elevation where you stand?
You can then calculate it from the spot you are standing using that temperature, pressure and known elevation data from topo map.

Then figure PA to get DA

Pressure altitude = (standard pressure- your current pressure setting)x1000+ your field elevation.
Then Density Altitude=Pressure Altitude + [120x(Outside Air Temperature in deg C-ISA Temperature always 15C)]

Point and click
 
Density altitude (and wind) is all that really matters to the bullet. Density altitude is calculated based off of a lot of the other environmental factors, and it is the altitude that the "bullet thinks it is at". Really that's the only environmental input you need (again, besides wind).
 
DA can change a lot as well. I was shooting at Rifles Only in Texas recently, and the elevation there is 73 feet. However, the DA was around 1700 feet when I was there. It's not uncommon for the DA in Texas to get as high as ~4500 feet at times. That's a big change.
 
Shibby! said:
And humidity...

DA is great if you have an app that uses it and the gear to get it.

While it's no doubt the best, learning the basics isn't a bad thing either!
Click to expand...

Agreed!

DA aside, my big point was that you don't need to know your physical altitude and barometric pressure to calculate an accurate ballistic solution. Just use station pressure (set reference altitude to "0") and you will get the same result
 
You're in Edmonton. If this is important to you drive to the airport and park your car on the north end were the runway starts/ends. Calibrate there as the altitude is exact there +/- 1m
 
You must log in or register to reply here.
Back
Top Bottom