Thread: Barometric pressures at altitude

Some measured values people might find useful for setting up drop tables. These are just from a barometer app on my phone.

For my 7mm08 the drop at 300m is about 3cm less and the wind drift for 5m/s full crosswind is 6cm less at 1500mthan at sea level.

I make up my chart for 500mASL and include a note with the correction for 300m at 1500m.


Waihohonu hut
Alt 1150m
Temp 10.5C
Baro 888hPa
Wind 2m/s

Rangipo hut
Alt 1550m ASL
Temp 8.8C
Baro 841hPa
Wind 4 m/s

Mangaehuehu hut
Alt 1280m ASL
Temp 12.8C
Baro 873 hPa
Wind 2.5 m/s

If someone could post measured pressures at 2000m and 2500m or a link to an online reference table that would be interesting,thanks.

https://keisan.casio.com/exec/system/1224579725

Altitude alone can be a very inaccurate indicator of air pressure

Relative air pressure is what you need to focus on, measure it with a device that doesn’t convert altitude into air pressure readings

PS: Most hunters can use an average of 28inhg and harvest a lot of deer

Thanks @Puffin that calculator agrees with all three of my measurements closer than 5 hPa.

Whats the device youve got in that pic Saum ?

Im pretty sure phones will be measuring station pressure ie actual pressure on site not calculating from GPS altitude. The appis supposed to be used to track trend over time too (although ive never been patient enough to get a good trace of it).

It’s a Skywatcher Explorer 4
Relative Baro , temp, air speed etc, metric and imperial readings

Ok you've made me ask. Whats “relative air pressure” ? Is it density altitude, percent of sea level etc ? Where do you put it in a ballistic calculator ?

Station pressure is the awnser ,
What was the question?
This is why I love the kestrel as it's all done for you.
My samsung phone has station pressure sensor but no thermometer.
You can just guess that

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Originally Posted by andyanimal31

Station pressure is the awnser ,
What was the question?
This is why I love the kestrel as it's all done for you.
My samsung phone has station pressure sensor but no thermometer.
You can just guess that

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This is on the samsung

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There are a bunch of ways to skin this cat depending on your app and skill set

Probably the easiest way is to measure your absolute air pressure with a barometer and enter that into your app. Often the app will then set the altitude to zero as alt is irrelevant after knowing the absolute air pressure

Absolute air pressure is the measured air pressure right where your standing, the reading taken with an actual hand held barometer.

Air pressure can change three times in an hour quite easily, without you even moving an inch

At the end of the day use what works for you

Andyanimal has extensive experience and has a system that’s reliable

Ultimately it is air density is what affects bullet drag.
This article is one of the best I have read that simply explains what happens and what inputs were needed.
Absolute air pressure is station pressure.

https://bisonballistics.com/articles...cs-calculators

A phone with an in built barometer measures station pressure nothing else.
With temperature and relative humidity values, density altitude can then be calculated.

Watches with barometer in them are getting cheap... Used one for years, also gives you a back up compass depending on the model

Use my watch for air pres(station pres) guess temp within 10 deg is close enough(but most people can guess within 5deg.) if you have correct air pres. and set humidity to 50%.

Originally Posted by blair993

Use my watch for air pres(station pres) guess temp within 10 deg is close enough(but most people can guess within 5deg.) if you have correct air pres. and set humidity to 50%.

Yep I agree that using your phone or watch for station pressure and guessing temp and 50% humidity is exactly what i would be doing if i didnt have the kestrel.
For $400 you can get the kestrel 2700 which has every thing you need for getting an accurate elevation and wind solution out to 875yds as has the compass and applied ballistics that you can purchase custom drag curves.
The only other good option i have used predominantly in the past is the 2500 kestrel and put that into your phone app manually which essentially gives you the same info except it's a lot slower than the 5700 and 2700.
If you really want to do your head in start looking at spin drift, aerodynamic jump and coriolis!

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