Is there an advantage or reason to use density altitude. I'm about to order a Kestrel and would rather order the 3500 to save considerably over the 4000 or 4500. The 3500 does baro. pressure, temp and humidity which is what density altitude is (a combination of these three), so why do I need it? Thanks
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Range Report Why density altitude?
- Thread starter CCooper
- Start date
Re: Why density altitude?
If you want the DA live you'll have to figure it each time. I have all the instruments to figure it out. But the next one I buy will be direct reading the DA. Probably the Kestrel 4000
If you want the DA live you'll have to figure it each time. I have all the instruments to figure it out. But the next one I buy will be direct reading the DA. Probably the Kestrel 4000
Re: Why density altitude?
I hope there will be some good input on this subject.
I had an interesting experience shooting 1000 yards in the fog this weekend.
My dope was almost 4 moa different than the last time I shot at this range.
I hope there will be some good input on this subject.
I had an interesting experience shooting 1000 yards in the fog this weekend.
My dope was almost 4 moa different than the last time I shot at this range.
Re: Why density altitude?
ask any pilot about density altitude and they will tell you about not wanting to be the first one at the scene of an accident .
for shooters that want to win and achieve them 1st round hits at distance knowing the DA is key to success
ask any pilot about density altitude and they will tell you about not wanting to be the first one at the scene of an accident .
for shooters that want to win and achieve them 1st round hits at distance knowing the DA is key to success
Re: Why density altitude?
Think about what a dope chart would look like if you entered each parameter(station pressure, temp and humidity)individually throughout a range of potential conditions. DA condenses all three into one usable number.
Think about what a dope chart would look like if you entered each parameter(station pressure, temp and humidity)individually throughout a range of potential conditions. DA condenses all three into one usable number.
Re: Why density altitude?
+1. Depending on your external ballistics software, you may be able to enter only the DA and not all three numbers. Some ballistics graphs use only the DA, so it's the most useful number to have.
+1. Depending on your external ballistics software, you may be able to enter only the DA and not all three numbers. Some ballistics graphs use only the DA, so it's the most useful number to have.
Re: Why density altitude?
I would not think pressure, temp and humidity would change that much, that fast, but I may be wrong. I just loaded bulletflight on my Itouch and it doesn't have an input for DA, just pressure, temp and humidity. Is DA more accurate than inputting pressure, temp and humidity independently?
I would not think pressure, temp and humidity would change that much, that fast, but I may be wrong. I just loaded bulletflight on my Itouch and it doesn't have an input for DA, just pressure, temp and humidity. Is DA more accurate than inputting pressure, temp and humidity independently?
Re: Why density altitude?
All of these programs determine air density, which is needed for the drag calculation. You can get air density from temp, pressure and humidity, or from DA.
All of these programs determine air density, which is needed for the drag calculation. You can get air density from temp, pressure and humidity, or from DA.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CCooper</div><div class="ubbcode-body">I would not think pressure, temp and humidity would change that much, that fast, but I may be wrong. I just loaded bulletflight on my Itouch and it doesn't have an input for DA, just pressure, temp and humidity. Is DA more accurate than inputting pressure, temp and humidity independently? </div></div>
Go to JBM and play around with the DA card page. You can see what DA does at longer ranges.
JBM DA card
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CCooper</div><div class="ubbcode-body">I would not think pressure, temp and humidity would change that much, that fast, but I may be wrong. I just loaded bulletflight on my Itouch and it doesn't have an input for DA, just pressure, temp and humidity. Is DA more accurate than inputting pressure, temp and humidity independently? </div></div>
Go to JBM and play around with the DA card page. You can see what DA does at longer ranges.
JBM DA card
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">... so why do I need it?</div></div>
DA is calculated using temperature, atmospheric pressure, and humidity, which the 3500 measures.
If you are going to carry an electronic device with a ballistics program into the field, there is no need to have something which computes the density altitude - just enter the temperature, pressure, and relative humidity.
However, if you don't want to deploy a device with a ballistic program to the field, or you want a backup for that device should it fail, then it's useful to build a DA dope table and use a Kestrel with a DA calculation.
There are manual methods for calculating DA - see Manual Calculation of Density Altitude. However, those methods will not be as accurate for long shots as having the Kestrel do the calculation.
If you would like some information on building your own DA elevation table, see Making Ballistic Cards Using Density Altitude.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">... so why do I need it?</div></div>
DA is calculated using temperature, atmospheric pressure, and humidity, which the 3500 measures.
If you are going to carry an electronic device with a ballistics program into the field, there is no need to have something which computes the density altitude - just enter the temperature, pressure, and relative humidity.
However, if you don't want to deploy a device with a ballistic program to the field, or you want a backup for that device should it fail, then it's useful to build a DA dope table and use a Kestrel with a DA calculation.
There are manual methods for calculating DA - see Manual Calculation of Density Altitude. However, those methods will not be as accurate for long shots as having the Kestrel do the calculation.
If you would like some information on building your own DA elevation table, see Making Ballistic Cards Using Density Altitude.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CCooper</div><div class="ubbcode-body">I would not think pressure, temp and humidity would change that much, that fast, but I may be wrong. </div></div>
yup you're are wrong........well lets just say its happened to competitors in these ukd/LD games and in several hunting scenarios that i have been to.......it only takes a kick in the ass once and then you learn
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CCooper</div><div class="ubbcode-body">I would not think pressure, temp and humidity would change that much, that fast, but I may be wrong. </div></div>
yup you're are wrong........well lets just say its happened to competitors in these ukd/LD games and in several hunting scenarios that i have been to.......it only takes a kick in the ass once and then you learn
Re: Why density altitude?
Yep. I was running the stage for the 1000 yard shot at a Rifles Only match. Shooters were mostly missing low. After all shooters were through, I stood up on the tower and asked the crowd, "Did anyone check the barometric pressure?"
There were several groans and forehead smacks, and one guy who said, "Yeah - after I shot." The BP was 30.2. On a 1000 yard shot, it matters.
Yep. I was running the stage for the 1000 yard shot at a Rifles Only match. Shooters were mostly missing low. After all shooters were through, I stood up on the tower and asked the crowd, "Did anyone check the barometric pressure?"
There were several groans and forehead smacks, and one guy who said, "Yeah - after I shot." The BP was 30.2. On a 1000 yard shot, it matters.
Re: Why density altitude?
What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.
What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.
Re: Why density altitude?
It may not be as precise, but there is a chart I keep in my fieldbook from the density altitute wiki page on that has been consistantly within 500' DA of other shooters Kestrel's when I use it. I just guess the actual temperature and get the elev. from a topo map. I think thats good enough for a backup at least if not Good enough and faster than digging for another instrument inside of 1000 yds. I only know about shooting steel plates and furry critters so military/PO may differ. I realize that this may fall apart and not be good enough for you guys shooting the heavies over 1400yds.
It may not be as precise, but there is a chart I keep in my fieldbook from the density altitute wiki page on that has been consistantly within 500' DA of other shooters Kestrel's when I use it. I just guess the actual temperature and get the elev. from a topo map. I think thats good enough for a backup at least if not Good enough and faster than digging for another instrument inside of 1000 yds. I only know about shooting steel plates and furry critters so military/PO may differ. I realize that this may fall apart and not be good enough for you guys shooting the heavies over 1400yds.
Re: Why density altitude?
It's not a bad chart, but it still requires that you use the pressure altitude rather than the physical altitude.
A 1000 foot error in DA will result in abouta 1.25 MOA error on a 1000 foot shot from a typical .308, so it's a good idea to be as accurate as possible.
The chart in my article Manual Calculation of Density Altitude may be a little easier to use.
It's not a bad chart, but it still requires that you use the pressure altitude rather than the physical altitude.
A 1000 foot error in DA will result in abouta 1.25 MOA error on a 1000 foot shot from a typical .308, so it's a good idea to be as accurate as possible.
The chart in my article Manual Calculation of Density Altitude may be a little easier to use.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.</div></div>
The new update for Ballistic FTE allows for D/A input.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.</div></div>
The new update for Ballistic FTE allows for D/A input.
Re: Why density altitude?
Thanks Lindy for a great explanation. I believe I will go ahead and get the 4000 so I can build a DA dope table for backup.
<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">... so why do I need it?</div></div>
DA is calculated using temperature, atmospheric pressure, and humidity, which the 3500 measures.
If you are going to carry an electronic device with a ballistics program into the field, there is no need to have something which computes the density altitude - just enter the temperature, pressure, and relative humidity.
However, if you don't want to deploy a device with a ballistic program to the field, or you want a backup for that device should it fail, then it's useful to build a DA dope table and use a Kestrel with a DA calculation.
There are manual methods for calculating DA - see Manual Calculation of Density Altitude. However, those methods will not be as accurate for long shots as having the Kestrel do the calculation.
If you would like some information on building your own DA elevation table, see Making Ballistic Cards Using Density Altitude.
</div></div>
Thanks Lindy for a great explanation. I believe I will go ahead and get the 4000 so I can build a DA dope table for backup.
<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">... so why do I need it?</div></div>
DA is calculated using temperature, atmospheric pressure, and humidity, which the 3500 measures.
If you are going to carry an electronic device with a ballistics program into the field, there is no need to have something which computes the density altitude - just enter the temperature, pressure, and relative humidity.
However, if you don't want to deploy a device with a ballistic program to the field, or you want a backup for that device should it fail, then it's useful to build a DA dope table and use a Kestrel with a DA calculation.
There are manual methods for calculating DA - see Manual Calculation of Density Altitude. However, those methods will not be as accurate for long shots as having the Kestrel do the calculation.
If you would like some information on building your own DA elevation table, see Making Ballistic Cards Using Density Altitude.
</div></div>
Re: Why density altitude?
Thanks for the info! I like that chart much better!!! Zak Smith seems to have one in printible form as well.
Kestrels are very good kit, just trying to get by with a cracker jack budget with caviar taste until the two match. Looks like I need a simple altimeter to get the station pressure or pressure altitude at least.
http://demigodllc.com/icao.pdf
^^^^^Link
Thanks for the info! I like that chart much better!!! Zak Smith seems to have one in printible form as well.
Kestrels are very good kit, just trying to get by with a cracker jack budget with caviar taste until the two match. Looks like I need a simple altimeter to get the station pressure or pressure altitude at least.
http://demigodllc.com/icao.pdf
^^^^^Link
Re: Why density altitude?
Ladies and Gentlemen:
First of all, I would like to let you all know that to the best of my knowledge LoadBase 3.0 from Patagoniaballistics.com is the only ballistic program that will readily take a DA (Density Altitude) value for both, desktop version and mobile (pda) version for <span style="color: #FF0000">sight-in conditions </span>and <span style="color: #FF0000">field conditions</span>.
On 4/19/2009 I wrote a post with this type of info. I hope it will help someone
--------------------------------------------------------------------------------
Please click on the link below.
Scroll down to the sixth post by Eaglet.
DENSITY ALTITUDE
Ladies and Gentlemen:
First of all, I would like to let you all know that to the best of my knowledge LoadBase 3.0 from Patagoniaballistics.com is the only ballistic program that will readily take a DA (Density Altitude) value for both, desktop version and mobile (pda) version for <span style="color: #FF0000">sight-in conditions </span>and <span style="color: #FF0000">field conditions</span>.
On 4/19/2009 I wrote a post with this type of info. I hope it will help someone
--------------------------------------------------------------------------------
Please click on the link below.
Scroll down to the sixth post by Eaglet.
DENSITY ALTITUDE
Re: Why density altitude?
The problem with Zak's chart is that it doesn't take into account variations in atmospheric pressure at a given altitude - and we know it varies.
When I don't want to carry a Kestrel or need a backup, I just use the station pressure from the sensor in my Casio Pathfinder watch, and use the methods in the article on manual calculation of DA.
The problem with Zak's chart is that it doesn't take into account variations in atmospheric pressure at a given altitude - and we know it varies.
When I don't want to carry a Kestrel or need a backup, I just use the station pressure from the sensor in my Casio Pathfinder watch, and use the methods in the article on manual calculation of DA.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: edgewater</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.</div></div>
The new update for Ballistic FTE allows for D/A input. </div></div>
Where is it? I have the latest ver of Ballistic FTE on my iphone and I see no input for DA.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: edgewater</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.</div></div>
The new update for Ballistic FTE allows for D/A input. </div></div>
Where is it? I have the latest ver of Ballistic FTE on my iphone and I see no input for DA.
Re: Why density altitude?
There is not much need for it.
If you have a Kestrel to calculate the DA for you, it will also tell you the temperature, pressure, and RH, which you can enter directly.
The real use of DA is to make a backup chart for when your electronic gizmo goes tits-up.
There is not much need for it.
If you have a Kestrel to calculate the DA for you, it will also tell you the temperature, pressure, and RH, which you can enter directly.
The real use of DA is to make a backup chart for when your electronic gizmo goes tits-up.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: edgewater</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.</div></div>
The new update for Ballistic FTE allows for D/A input. </div></div>
Where is it? I have the latest ver of Ballistic FTE on my iphone and I see no input for DA.</div></div> You have to change it in your settings. Once changed you have redo your loads and save them in your favorites. The program will not allow you to put in your current atmospheric conditions in D/A if they were stored into your favorites using temp, alt, pressure and humidity.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: edgewater</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">What electronic ballistic programs that you can take in the field accept DA directly? I know KAC Bulletflight and Ballistic FTE do not take raw DA.</div></div>
The new update for Ballistic FTE allows for D/A input. </div></div>
Where is it? I have the latest ver of Ballistic FTE on my iphone and I see no input for DA.</div></div> You have to change it in your settings. Once changed you have redo your loads and save them in your favorites. The program will not allow you to put in your current atmospheric conditions in D/A if they were stored into your favorites using temp, alt, pressure and humidity.
Re: Why density altitude?
In the ANALYZER MODULE (Atmosphere Tab) of LB3D, it calculates a table of DA taking in consideration:
1) Humidity
2) Allows you to calculate DA using Pressure, Altitude or Station Pressure
3) Output in English or Metric
4) Follows the NOAA model
Here is a screen shot of part of it.
In the ANALYZER MODULE (Atmosphere Tab) of LB3D, it calculates a table of DA taking in consideration:
1) Humidity
2) Allows you to calculate DA using Pressure, Altitude or Station Pressure
3) Output in English or Metric
4) Follows the NOAA model
Here is a screen shot of part of it.
Re: Why density altitude?
Lindy,
I like your many additional explanations than my own. I know what I want to say. I just don't have as much experience with it as you do.
Again, good job.
Lindy,
I like your many additional explanations than my own. I know what I want to say. I just don't have as much experience with it as you do.
Again, good job.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rmfield</div><div class="ubbcode-body">NOAA??
Perhaps you meant ICAO.
Edit deleted. </div></div>
(NOAA) = National Oceanic and Atmospheric Administration
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rmfield</div><div class="ubbcode-body">NOAA??
Perhaps you meant ICAO.
Edit deleted. </div></div>
(NOAA) = National Oceanic and Atmospheric Administration
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">(NOAA) = National Oceanic and Atmospheric Administration</div></div>
Well, I'm afraid that turns out not to be the case.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.</div></div>
Density altitude, by definition, refers to the Standard Atmosphere established by the International Civil Aviation Organization.
NOAA has nothing to do with it.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">(NOAA) = National Oceanic and Atmospheric Administration</div></div>
Well, I'm afraid that turns out not to be the case.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.</div></div>
Density altitude, by definition, refers to the Standard Atmosphere established by the International Civil Aviation Organization.
NOAA has nothing to do with it.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">The real use of DA is to make a backup chart for when your electronic gizmo goes tits-up.
</div></div>
Ballistic has this under its Settings > JBM Computer > Format. But I have to agree with Lindy: Why? Now if it generated a chart like the online version of JBM does, then it could at least be printed out for a backup. But AFAIK there isn't any provision for that so it seems kind of useless.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">The real use of DA is to make a backup chart for when your electronic gizmo goes tits-up.
</div></div>
Ballistic has this under its Settings > JBM Computer > Format. But I have to agree with Lindy: Why? Now if it generated a chart like the online version of JBM does, then it could at least be printed out for a backup. But AFAIK there isn't any provision for that so it seems kind of useless.
Re: Why density altitude?
<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">(NOAA) = National Oceanic and Atmospheric Administration</div></div>
Well, I'm afraid that turns out not to be the case.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.</div></div>
Density altitude, by definition, refers to the Standard Atmosphere established by the International Civil Aviation Organization.
NOAA has nothing to do with it.
</div></div>
NOAA is in charge of defining the mathematical models of the atmosphere.
These models are the "standard" ICAO adapts them to their own needs.
ICAO can define what they consider to be their standard atmosphere, but it’s not their function to define the climatological models.
In other words, ICAO is a USER of the models of NOAA and not the other way round …
NOAA is the “Owner” of the “standards”. ICAO does not deal with climate models, equations, etc
<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">(NOAA) = National Oceanic and Atmospheric Administration</div></div>
Well, I'm afraid that turns out not to be the case.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.</div></div>
Density altitude, by definition, refers to the Standard Atmosphere established by the International Civil Aviation Organization.
NOAA has nothing to do with it.
</div></div>
NOAA is in charge of defining the mathematical models of the atmosphere.
These models are the "standard" ICAO adapts them to their own needs.
ICAO can define what they consider to be their standard atmosphere, but it’s not their function to define the climatological models.
In other words, ICAO is a USER of the models of NOAA and not the other way round …
NOAA is the “Owner” of the “standards”. ICAO does not deal with climate models, equations, etc
Re: Why density altitude?
NOAA is in charge of fitting climate data to the hockey stick, hiding the decline and other such dubious distictions.
NOAA is in charge of fitting climate data to the hockey stick, hiding the decline and other such dubious distictions.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">ICAO can define what they consider to be their standard atmosphere... </div></div>
Not only <span style="font-style: italic">can</span> they, but they <span style="font-style: italic">did</span> - which is why it's referred to as the <span style="font-style: italic">ICAO Standard Atmosphere.</span>
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...but it’s not their function to define the climatological models.</div></div>
Agreed. But we weren't discussing climatological models, just density altitude.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">ICAO can define what they consider to be their standard atmosphere... </div></div>
Not only <span style="font-style: italic">can</span> they, but they <span style="font-style: italic">did</span> - which is why it's referred to as the <span style="font-style: italic">ICAO Standard Atmosphere.</span>
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...but it’s not their function to define the climatological models.</div></div>
Agreed. But we weren't discussing climatological models, just density altitude.
Re: Why density altitude?
<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">ICAO can define what they consider to be their standard atmosphere... </div></div>
Not only <span style="font-style: italic">can</span> they, but they <span style="font-style: italic">did</span> - which is why it's referred to as the <span style="font-style: italic">ICAO Standard Atmosphere.</span>
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...but it’s not their function to define the climatological models.</div></div>
Agreed. But we weren't discussing climatological models, just density altitude.
</div></div>
Lindy,
First I post this:
<span style="color: #000099">In the ANALYZER MODULE (Atmosphere Tab) of LB3D, it calculates a table of DA taking in consideration:
1) Humidity
2) Allows you to calculate DA using Pressure, Altitude or Station Pressure
3) Output in English or Metric
4) Follows the NOAA model</span>
Then I’m questioned about NOAA and when I replied you stated it had nothing to do with it; I responded with facts:
<span style="color: #000099">NOAA is in charge of defining the mathematical models of the atmosphere.
These models are the "standard" ICAO adapts them to their own needs.
ICAO can define what they consider to be their standard atmosphere, but it’s not their function to define the climatological models.
In other words, ICAO is a USER of the models of NOAA and not the other way round …
NOAA is the “Owner” of the “standards”. ICAO does not deal with climate models, equations, etc</span>
Then you say:
Agreed. But we weren't discussing climatological models, just density altitude.
<span style="color: #990000">Can you see something wrong with the above picture?</span>
<span style="color: #000099">All I was doing was providing accurate information as to how LB3D follows the NOAA model to calculate accurate density altitude. Climatological models play an indispensable part in “Density Altitude”.
I’m done here you can have the box to your self and I apologize if in any way I offended any one. </span>
<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">ICAO can define what they consider to be their standard atmosphere... </div></div>
Not only <span style="font-style: italic">can</span> they, but they <span style="font-style: italic">did</span> - which is why it's referred to as the <span style="font-style: italic">ICAO Standard Atmosphere.</span>
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...but it’s not their function to define the climatological models.</div></div>
Agreed. But we weren't discussing climatological models, just density altitude.
</div></div>
Lindy,
First I post this:
<span style="color: #000099">In the ANALYZER MODULE (Atmosphere Tab) of LB3D, it calculates a table of DA taking in consideration:
1) Humidity
2) Allows you to calculate DA using Pressure, Altitude or Station Pressure
3) Output in English or Metric
4) Follows the NOAA model</span>
Then I’m questioned about NOAA and when I replied you stated it had nothing to do with it; I responded with facts:
<span style="color: #000099">NOAA is in charge of defining the mathematical models of the atmosphere.
These models are the "standard" ICAO adapts them to their own needs.
ICAO can define what they consider to be their standard atmosphere, but it’s not their function to define the climatological models.
In other words, ICAO is a USER of the models of NOAA and not the other way round …
NOAA is the “Owner” of the “standards”. ICAO does not deal with climate models, equations, etc</span>
Then you say:
Agreed. But we weren't discussing climatological models, just density altitude.
<span style="color: #990000">Can you see something wrong with the above picture?</span>
<span style="color: #000099">All I was doing was providing accurate information as to how LB3D follows the NOAA model to calculate accurate density altitude. Climatological models play an indispensable part in “Density Altitude”.
I’m done here you can have the box to your self and I apologize if in any way I offended any one. </span>
Re: Why density altitude?
Eaglet:
Any involvement of NOAA in the development of the ICAO Standard Atmosphere is irrelevant. The important issue for users of ballistic software is to distinguish between the Metro Standard and ICAO Standard Conditions. Many software programs default to Metro Standard Conditions and this confuses people because DA is based on ICAO Standard Conditions. I won't go into the details on this as I think Lindy covers it on his site.
In any case, the reason I originally asked if you meant to say "ICAO", is that "NOAA" wasn't meaningful information in the context of the subject here.
Eaglet:
Any involvement of NOAA in the development of the ICAO Standard Atmosphere is irrelevant. The important issue for users of ballistic software is to distinguish between the Metro Standard and ICAO Standard Conditions. Many software programs default to Metro Standard Conditions and this confuses people because DA is based on ICAO Standard Conditions. I won't go into the details on this as I think Lindy covers it on his site.
In any case, the reason I originally asked if you meant to say "ICAO", is that "NOAA" wasn't meaningful information in the context of the subject here.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rmfield</div><div class="ubbcode-body">Eaglet:
Any involvement of NOAA in the development of the ICAO Standard Atmosphere is irrelevant. The important issue for users of ballistic software is to distinguish between the Metro Standard and ICAO Standard Conditions. Many software programs default to Metro Standard Conditions and this confuses people because DA is based on ICAO Standard Conditions. I won't go into the details on this as I think Lindy covers it on his site.
In any case, the reason I originally asked if you meant to say "ICAO", is that "NOAA" wasn't meaningful information in the context of the subject here. </div></div>
rmfield,
I was not planning on posting anymore, but I don't believe it's right to ignore you and your post, though I've done that in the past when I know it just won't help anymore...
<span style="font-weight: bold">Here is some information I managed to obtain:</span>
1) The point here is NOT what Standard Atmosphere is accounted for. That will make for another thread.
2) DA, as an atmospheric parameter, is NOT related to ANY “standard atmosphere”, the same as Temperature or Humidity by themselves.
3) It’s like saying that the Absolute ZERO is related to Army/Metro or ICAO…DA is a relationship between several parameters, most important the “Pressure Altitude”
4) Granted, most airplanes have their instruments generally calibrated for ICAO standard Conditions (Sea Level, 15 ºC, Standard Adiabatic Lapse Rate, etc.)
5) However, DA can be related to ANY “standard atmosphere”, ICAO is the most known in Ballistics, aeronautics, etc, but hardly the only one.
6) The ICAO Standard Atmosphere has long been used by the aviation community and other practical applications to specify how pressure declines with true altitude. However this model was never intended to accurately predict Pressure Altitude under a wide range of environmental conditions.
7) <span style="color: #000099">NOAA <span style="font-weight: bold">is relevant </span>in terms of what model the DA equations are based on.</span>
8) As we all know, there is a simplified way to calculate DA. So, what LB3D does is based on the exact model, defined by the competent authority, which is NOAA.
From Wikipedia (public reference)
9) Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.
Both an increase in temperature and humidity will cause a reduction in air density. Thus, in hot and humid conditions, the density altitude at a particular location may be significantly higher than the true altitude.
10) The International Standard Atmosphere (ISA) is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes. It consists of tables of values at various altitudes, plus some formulas by which those values were derived. The International Organization for Standardization (ISO), publishes the ISA as an international standard, ISO 2533:1975
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rmfield</div><div class="ubbcode-body">Eaglet:
Any involvement of NOAA in the development of the ICAO Standard Atmosphere is irrelevant. The important issue for users of ballistic software is to distinguish between the Metro Standard and ICAO Standard Conditions. Many software programs default to Metro Standard Conditions and this confuses people because DA is based on ICAO Standard Conditions. I won't go into the details on this as I think Lindy covers it on his site.
In any case, the reason I originally asked if you meant to say "ICAO", is that "NOAA" wasn't meaningful information in the context of the subject here. </div></div>
rmfield,
I was not planning on posting anymore, but I don't believe it's right to ignore you and your post, though I've done that in the past when I know it just won't help anymore...
<span style="font-weight: bold">Here is some information I managed to obtain:</span>
1) The point here is NOT what Standard Atmosphere is accounted for. That will make for another thread.
2) DA, as an atmospheric parameter, is NOT related to ANY “standard atmosphere”, the same as Temperature or Humidity by themselves.
3) It’s like saying that the Absolute ZERO is related to Army/Metro or ICAO…DA is a relationship between several parameters, most important the “Pressure Altitude”
4) Granted, most airplanes have their instruments generally calibrated for ICAO standard Conditions (Sea Level, 15 ºC, Standard Adiabatic Lapse Rate, etc.)
5) However, DA can be related to ANY “standard atmosphere”, ICAO is the most known in Ballistics, aeronautics, etc, but hardly the only one.
6) The ICAO Standard Atmosphere has long been used by the aviation community and other practical applications to specify how pressure declines with true altitude. However this model was never intended to accurately predict Pressure Altitude under a wide range of environmental conditions.
7) <span style="color: #000099">NOAA <span style="font-weight: bold">is relevant </span>in terms of what model the DA equations are based on.</span>
8) As we all know, there is a simplified way to calculate DA. So, what LB3D does is based on the exact model, defined by the competent authority, which is NOAA.
From Wikipedia (public reference)
9) Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.
Both an increase in temperature and humidity will cause a reduction in air density. Thus, in hot and humid conditions, the density altitude at a particular location may be significantly higher than the true altitude.
10) The International Standard Atmosphere (ISA) is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes. It consists of tables of values at various altitudes, plus some formulas by which those values were derived. The International Organization for Standardization (ISO), publishes the ISA as an international standard, ISO 2533:1975
Re: Why density altitude?
Eaglet:
I appreciate all of that, but debating those points serves no purpose here. Like you, I am fairly knowledgable about the physics of the atmosphere, but the vast majority of that knowledge is academic and of little use in long range shooting.
The thread is about the usefulness of DA in long range shooting.
DA is useful for making a series of tables for a variety of different atmospheric conditions, assuming the range of the shots is not too great and the size of the targets is not too small.
As you know DA combines the effects of pressure, temperature and humidity into a single parameter. It allows the shooter to produce a set of tables that covers a wide range of atmosperic conditions without having to consider the infinite number of temperature, pressure and humidity permutations possible. If the DA is 8,411 feet, the shooter can choose the table that is nearest to this, say his DA=8000' table, and be reasonably accurate (+/- 1/4 MOA) out to 1,000 yards. It doesn't matter if the actual DA is off by a few hundred feet, so it doesn't much matter how sophisticated your DA calculations are. Obviously, the velocity and BC of the bullet will influence the limits of this method.
In any case, if this method is not precise enough for the shot you are taking, then you probably shouldn't be using DA tables. You should use a computer and input the actual temperature, pressure and humidity.
Using DA in long range shooting isn't complicated, but it can be confusing. It serves no purpose to make it more complicated than necessary.
Eaglet:
I appreciate all of that, but debating those points serves no purpose here. Like you, I am fairly knowledgable about the physics of the atmosphere, but the vast majority of that knowledge is academic and of little use in long range shooting.
The thread is about the usefulness of DA in long range shooting.
DA is useful for making a series of tables for a variety of different atmospheric conditions, assuming the range of the shots is not too great and the size of the targets is not too small.
As you know DA combines the effects of pressure, temperature and humidity into a single parameter. It allows the shooter to produce a set of tables that covers a wide range of atmosperic conditions without having to consider the infinite number of temperature, pressure and humidity permutations possible. If the DA is 8,411 feet, the shooter can choose the table that is nearest to this, say his DA=8000' table, and be reasonably accurate (+/- 1/4 MOA) out to 1,000 yards. It doesn't matter if the actual DA is off by a few hundred feet, so it doesn't much matter how sophisticated your DA calculations are. Obviously, the velocity and BC of the bullet will influence the limits of this method.
In any case, if this method is not precise enough for the shot you are taking, then you probably shouldn't be using DA tables. You should use a computer and input the actual temperature, pressure and humidity.
Using DA in long range shooting isn't complicated, but it can be confusing. It serves no purpose to make it more complicated than necessary.
Re: Why density altitude?
Not sure if I understand your question, but the propellant includes its own oxidizer. I find it hard to believe that the atmospheric concentration of O2 could have much influence on rate of propellant burn.
Edit
Some say that atmosperic temperature effects rate of burn (and velocity), but I believe that is true mostly because of its influence on the temperature of the propellant. Some disagree with me on this, but I believe you can control the influence of temperature by controlling the temp. of your ammo - including how long you let it sit in a hot chamber.
Not sure if I understand your question, but the propellant includes its own oxidizer. I find it hard to believe that the atmospheric concentration of O2 could have much influence on rate of propellant burn.
Edit
Some say that atmosperic temperature effects rate of burn (and velocity), but I believe that is true mostly because of its influence on the temperature of the propellant. Some disagree with me on this, but I believe you can control the influence of temperature by controlling the temp. of your ammo - including how long you let it sit in a hot chamber.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...influence on the temperature of the propellant.</div></div>
Yes. Guns will fire underwater because the powder contains its own oxidizer.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...influence on the temperature of the propellant.</div></div>
Yes. Guns will fire underwater because the powder contains its own oxidizer.
Re: Why density altitude?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rmfield</div><div class="ubbcode-body">Eaglet:
I appreciate all of that, but debating those points serves no purpose here. Like you, I am fairly knowledgable about the physics of the atmosphere, but the vast majority of that knowledge is academic and of little use in long range shooting.
The thread is about the usefulness of DA in long range shooting.
DA is useful for making a series of tables for a variety of different atmospheric conditions, assuming the range of the shots is not too great and the size of the targets is not too small.
As you know DA combines the effects of pressure, temperature and humidity into a single parameter. It allows the shooter to produce a set of tables that covers a wide range of atmosperic conditions without having to consider the infinite number of temperature, pressure and humidity permutations possible. If the DA is 8,411 feet, the shooter can choose the table that is nearest to this, say his DA=8000' table, and be reasonably accurate (+/- 1/4 MOA) out to 1,000 yards. It doesn't matter if the actual DA is off by a few hundred feet, so it doesn't much matter how sophisticated your DA calculations are. Obviously, the velocity and BC of the bullet will influence the limits of this method.
In any case, if this method is not precise enough for the shot you are taking, then you probably shouldn't be using DA tables. You should use a computer and input the actual temperature, pressure and humidity.
Using DA in long range shooting isn't complicated, but it can be confusing. It serves no purpose to make it more complicated than necessary.
</div></div>
1) I only limited my self to answer what I was questioned on… See previous posts.
2) I did never give my opinion on weather to use or not DA <span style="color: #000099">“The thread is about the usefulness of DA in long range shooting.”</span>
3) Since we’re here, if the model to calculate DA is the right one, then DA can perfectly replace the usual variables (Temp, Humidity and Baro/Stat Pressure)
4) <span style="color: #000099">“but the vast majority of that knowledge is academic and of little use in long range shooting.”</span> FALSE this is what this thread is about!!!
5) On the contrary!! It is precisely in LR situations where is VITAL to fully understand that factors (and methods) affect our ballistic. In short and medium distances, none of this makes any sense.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rmfield</div><div class="ubbcode-body">Eaglet:
I appreciate all of that, but debating those points serves no purpose here. Like you, I am fairly knowledgable about the physics of the atmosphere, but the vast majority of that knowledge is academic and of little use in long range shooting.
The thread is about the usefulness of DA in long range shooting.
DA is useful for making a series of tables for a variety of different atmospheric conditions, assuming the range of the shots is not too great and the size of the targets is not too small.
As you know DA combines the effects of pressure, temperature and humidity into a single parameter. It allows the shooter to produce a set of tables that covers a wide range of atmosperic conditions without having to consider the infinite number of temperature, pressure and humidity permutations possible. If the DA is 8,411 feet, the shooter can choose the table that is nearest to this, say his DA=8000' table, and be reasonably accurate (+/- 1/4 MOA) out to 1,000 yards. It doesn't matter if the actual DA is off by a few hundred feet, so it doesn't much matter how sophisticated your DA calculations are. Obviously, the velocity and BC of the bullet will influence the limits of this method.
In any case, if this method is not precise enough for the shot you are taking, then you probably shouldn't be using DA tables. You should use a computer and input the actual temperature, pressure and humidity.
Using DA in long range shooting isn't complicated, but it can be confusing. It serves no purpose to make it more complicated than necessary.
</div></div>
1) I only limited my self to answer what I was questioned on… See previous posts.
2) I did never give my opinion on weather to use or not DA <span style="color: #000099">“The thread is about the usefulness of DA in long range shooting.”</span>
3) Since we’re here, if the model to calculate DA is the right one, then DA can perfectly replace the usual variables (Temp, Humidity and Baro/Stat Pressure)
4) <span style="color: #000099">“but the vast majority of that knowledge is academic and of little use in long range shooting.”</span> FALSE this is what this thread is about!!!
5) On the contrary!! It is precisely in LR situations where is VITAL to fully understand that factors (and methods) affect our ballistic. In short and medium distances, none of this makes any sense.
Re: Why density altitude?
I think I understand your comments individually, but I can't seem to pull them together to see what you are driving at as a whole. How is it helpful to the guy trying to make himself and use a set a DA referenced data cards ?
I think I understand your comments individually, but I can't seem to pull them together to see what you are driving at as a whole. How is it helpful to the guy trying to make himself and use a set a DA referenced data cards ?
Re: Why density altitude?
Michael:
In the business and government worlds, a common saying is: "The primary motivation behind the writing of most memos is not the conveyance of information to the reader, but rather covering the ass of the writer."
On the Internet, it would be a bit different: "The primary motivation behind many forum posts is not the conveyance of information to the reader, but rather to display how much the writer knows."
Doesn't apply to either of <span style="font-style: italic">us</span>, but...
Michael:
In the business and government worlds, a common saying is: "The primary motivation behind the writing of most memos is not the conveyance of information to the reader, but rather covering the ass of the writer."
On the Internet, it would be a bit different: "The primary motivation behind many forum posts is not the conveyance of information to the reader, but rather to display how much the writer knows."
Doesn't apply to either of <span style="font-style: italic">us</span>, but...
Re: Why density altitude?
Gents, I don't know garbage, there's just a wealth of information out there if you're willing to go find it or get it from those that are knowledgeable.
rmfield,
the answer to your question is in this thread.
Gents, I don't know garbage, there's just a wealth of information out there if you're willing to go find it or get it from those that are knowledgeable.
rmfield,
the answer to your question is in this thread.
Re: Why density altitude?
Matters a lot in an airplane and my hybrid loses 9mpg in cold air. So I can only assume it affects bullets.
Matters a lot in an airplane and my hybrid loses 9mpg in cold air. So I can only assume it affects bullets.
Re: Why density altitude?
it matters a whole lot on an airplane! i found that out taking off from the grand canyon at 4pm one july afternnon. it matters with bullets too. if you keep your data and record density altitude when you shoot you will see the difference it makes. especially when the differences are extreme.
it matters a whole lot on an airplane! i found that out taking off from the grand canyon at 4pm one july afternnon. it matters with bullets too. if you keep your data and record density altitude when you shoot you will see the difference it makes. especially when the differences are extreme.
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