Range Report Station pressure VS entering all data

[Unknown]

I have a Kestrel that has been giving me fits. I set the unit to the local airport's (2-3 miles from my house and about 190 ft above sea level for both) reported data for pressure, and used very accurate altitude info for altitude. Yet, when I go places, the Kestrel seems to be all over the place with altitude. Even after I let it sit on my living room table for a half hour to adjust, the altitude goes up and down.

I called Kestrel, and they said to just use station pressure (rather than entering altitude, barometric pressure, and all the other data) as it will do the same thing for my shooting.

I guess I'm old school, but I think the guy at Kestrel was blowing me off rather than accepting my unit in for repair.

I set my altitude at both places on the unit while I had the KEstrel customer service guy on the phone. Within a half hour, the altitude was going either up or down by 50-100 feet. The Kestrel rep says that is because of changes in the environment. He said that when I set the altitude and pressure, and one of them changes, that everything else changes.

So I asked him how I am supposed to use the unit to get altitude if I go somewhere else? He says that I have to reset the entire unit to local conditions when I go anywhere. My response was that if I have to get all the data by calling the weather service, or use an airport's reported data, there is no use or benefit to having the Kestrel because I bought it to provide me with that data. That was when he said to just use station pressure as it will do the same thing, and will coordinate with my exbal ballistics handheld unit.

Does any of this make sense to anyone else, or was I right that he was blowing smoke?

 

[EXTREMEPREJUDICE]

Re: Station pressure VS entering all data

Sorry to inform you but this is accurate. The unit dermines altitude by "pressure" so changes in barometric pressure will be reflected as a change in "altitude" and vice-versa. It is explained in the instructions (of course we usually don't read them in enough detail.) Usually barometric pressure changes rather slowly but of course it does change. Using station pressure solves the problem relative to your ballistic calculations but won't solve the problem the way you want it to.

 

[Ledzep]

Re: Station pressure VS entering all data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Unknown</div><div class="ubbcode-body">I have a Kestrel that has been giving me fits. I set the unit to the local airport's (2-3 miles from my house and about 190 ft above sea level for both) reported data for pressure, and used very accurate altitude info for altitude. Yet, when I go places, the Kestrel seems to be all over the place with altitude. Even after I let it sit on my living room table for a half hour to adjust, the altitude goes up and down.

I called Kestrel, and they said to just use station pressure (rather than entering altitude, barometric pressure, and all the other data) as it will do the same thing for my shooting.

I guess I'm old school, but I think the guy at Kestrel was blowing me off rather than accepting my unit in for repair.

I set my altitude at both places on the unit while I had the KEstrel customer service guy on the phone. Within a half hour, the altitude was going either up or down by 50-100 feet. The Kestrel rep says that is because of changes in the environment. He said that when I set the altitude and pressure, and one of them changes, that everything else changes.

So I asked him how I am supposed to use the unit to get altitude if I go somewhere else? He says that I have to reset the entire unit to local conditions when I go anywhere. My response was that if I have to get all the data by calling the weather service, or use an airport's reported data, there is no use or benefit to having the Kestrel because I bought it to provide me with that data. That was when he said to just use station pressure as it will do the same thing, and will coordinate with my exbal ballistics handheld unit.

Does any of this make sense to anyone else, or was I right that he was blowing smoke? </div></div>

What Kestrel told you was correct. Altimeters read barometric pressure. Barometric pressure can change quite a bit over several hours. Mine usually goes off a couple hundred feet over 24 hours.

Changes in weather (pressure) change altimeter readings. Nothing you can do about it. Every time a plane lands, it adjusts it's altimeter to the current airport weather info.

For shooting, altitude means practically NOTHING. Barometric pressure is the important part. For example, go on JBM and plug in all the data for your current environmentals (including baro pressure. Make sure pressure is not corrected for elevation), altitude, and gun. Then change the altitude, keeping the same pressure. You shouldn't see a difference in the read-out.

So to get baro pressure on your kestrel, go to the barometric pressure on the unit, then set the altitude for "0". That will give you accurate station pressure.

 

[EMorr]

Re: Station pressure VS entering all data

Made a mistake the above posts are correct.

 

[GrantB]

Re: Station pressure VS entering all data

Ballistic programs are only worried about air density (not altitude) but it can interpolate density from altitude. Station pressure is a more accurate way of inputing this data.

 

[Unknown]

Re: Station pressure VS entering all data

What is posted, is exactly what the guy at Kestrel told me. The reason for my skepticism is that normally, if something sounds too good to be true, it IS too good to be true. Using station pressure would be TONS easier for the calculations.

This is fabulous news, thanks for the confirmation. For what it is worth, I tried it both ways, and both ways did work out, but the old way is far more complex to figure. I figured that I just didn't have a long enough distance (550 yards) for a subtle difference to show itself.

Going with station pressure sure makes things a great deal more simple.

 

[azimutha]

Re: Station pressure VS entering all data

As mentioned, one of the best things about using station pressure is always getting to leave altitude set to zero. No conversion = no calibration...although I will sometimes calibrate my GPS at the house since I know the altitude within 6".

 

[Killer Spade 13]

Re: Station pressure VS entering all data

So, since my Kestrel gives out the ambient density altitude based on temperature, humidity and barometric pressure, that's all I need to know????

Write my dope card with nothing but range/density altitude relationships?

 

[WhiskeyWebber]

Re: Station pressure VS entering all data

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Killer Spade 13</div><div class="ubbcode-body">So, since my Kestrel gives out the ambient density altitude based on temperature, humidity and barometric pressure, that's all I need to know????

Write my dope card with nothing but range/density altitude relationships? </div></div>

Yep, that's what I do. Density altitude takes all of that stuff into account.

 

[Augustus]

Re: Station pressure VS entering all data

Well, I too am having trouble with the Atrag in the Kestrel. I have used Atrag in a Nomad using a Kestrel for years. I have always used Barometric pressure corrected for altitude and the solutions were very close to actual drops.

I purchased a new 4500 with Atrag and started playing with it. I read the instructions concerning station pressure and set the unit up by setting the altitude to zero then activated the auto function.

I put several of my rifles in the library and started looking at the solutions. They were way off. The solution for my 338/408 shooting 300 SMKs at 3150 was off by just under a mil at 1760.

The only way I can get close to the correct drops is to use Barometric pressure corrected for altitude, even with this method it is still off by .2 to .3 mil at 1760 .

I ran through solutions for all my rifles with similar results. Conclusion: if I use barometric pressure with the altitude set to zero the solutions are unusable.

I don't claim to be a genius when it comes to electronic gadgets,if anybody has suggestions Im in the listening mood.

 

[Augustus]

Re: Station pressure VS entering all data

Ok, I don't know what has changed but I played with the two systems this morning and the Nomad with Atrag using barometric pressure corrected for elevation is running very close to the kestrel using barometric pressure with altitude set to zero.

I can't explain the changes in results from last night but it seems to be ok now.

 

[hrt4me]

Re: Station pressure VS entering all data

interesting

 

[Augustus]

Re: Station pressure VS entering all data

Played with the two systems a little more this afternoon. The Kestrel works pretty close as long as Barometric pressure with altitude set to zero is used. The Nomad with Atrag works with Barometric pressure corrected for altitude. If used this way the Kestrel indicates .1 to .2 mils more correction than the Nomad at supersonic velocities. As the bullet approaches transonic velocities the gap begins to close. By the time the bullets is sub-sonic the Nomad is indicating more correction than the Kestrel.

This is about to drive me nuts. I guess I need to pick one of the systems, throw the other one away and make corrections based on actual field data. This will work ok for making hits on targets but it makes getting a true BC for a given projectile just about impossible.

I guess that's what Radar and acoustics are for.

 

[Unknown]

Re: Station pressure VS entering all data

I live only about a mile from an airport, and can get really good weather info from them. I got the altitude info for my house from various sites and came within 10 feet...one said 180, another 190, and the last one 200.. So I set altitude at 190 feet. Even with all that effort, the Kestrel was pretty well useless when I drove 3 hours to a match in the central part of the state.

So I wanted something that would be more useful, hence my call to Kestrel, and the station pressure inquiry. That is what I'm going to use from now on.

It would be nice to know altitude though...but having the altitude setting change whenever the weather changes makes that useless. In the Puget sound area (I'm about 1-2 blocks from the water ) the weather is ALWAYS changing.

 

[killahog]

Re: Station pressure VS entering all data

I am new to the Ballistic programs and have learned alot from reading on this site, Thank you to those who share there information. The question I have is How do I use the Automatic Atmosphere function on the android when using (shooter) I don't have a kestral or a GPS Thanks