So I know we are supposed to buy a Kestrel, but one could just correct the weather data from the nearest source which are available on certain radios, or other sources such as the internet. It seems to be very difficult to find out exactly what changes are made to "un-corrected" or as (Kestrel calls it "station pressure") readings. I've seen 4 formulas that look quite different to me, but I did find a chart which I wonder if it is correct: http://novalynx.com/manuals/bp-elevation-correction-tables.pdf
The tricky part is that I don't know if temperature is taken into account when the correction is made by weather stations. Altitude certainly is.
There are a number of conversion websites but they go in the wrong direction from actual to corrected, and they don't really state what the weather people actually use.
Perhaps this is why Rex advised to make charts based on your area of operations? Maybe a pilot can weigh in here, but let me offer my two cents.
As best I can tell, unless a front is moving in, the barometric pressure at any distance you are likely to take a hasty shot at shouldn't change. The problem, as always, will be the wind at long distances.
Using a Kestrel, or in my case, a WeatherFlow weather meter will give you your atmospherics at your current location, while taking heat, altitude, and wind into consideration. I use the Density Altitude for now, but will be using charts when I get them in order.
If I recall correctly, weather forecasts use a corrected relative to sea level barometric pressure, but pilots use DA, in order not to crash into the side of the mountain they have to clear.
The long and short of it is, buy the Kestral if you can afford it, but make and used your charts for when batteries are a hot commodity. Also, if the web goes down and/or barometric pressure readings are only given to pilots, on missions, it would be good to have a thermometer and a barometer.
If a Kestrel is out of your price range, take a look at the WeatherFlow. It uses JBM Ballistics software. The meter and app cost just under $100.00.
I have reviewed the matter and now believe that the above referenced chart is correct and will allow conversion of weather reports to actual "station pressure". Basically you subtract the value for any elevation above sea level.
use a DA chart. I have one folded up in my rifle data book. While I usually use the DA from the kestrel, if it was to go down as long as I have a altimeter, map or way of knowing my altitude and the temp outside, then it will give me the DA. It's pretty accurate, not perfect but it will work for a minute of man..if you are a hunter you might be interested in that. The chart I use considers 50% RH since which is a average of my area, and since RM plays such a small role on effecting external performance. It may not be for you, but it couldnt hurt to try, and its only one number to put in then multiple values!
grant
I have that same chart but am confused on how to use it. I do not have a weather meter yet but would like to get some charts going in the meantime. Can you or anyone else explain to me how to use the chart to my advantage?
Try this. It will get you close. Just know your altitude and temp. Follow the squares that are closest to your conditions. Put that value of density altitude into your dope.
So my altitude to the right and my temperature at the bottom? And where the two meet is my density altitude?
Altitude is the center, temp is the bottom, DA is the left. You will notice the center of the square has a little tick in it, that is a half value. So it can be decently accurate. The humidity is at 50% because of how little it effects POI, so it is an average, but you can make one that is considered for other RH
Thank you for your help. I will give it a try.