Range Report A question about how barometric press. is reported

[TimK]

I'm new at this, which will probably be obvious from my question.

I'm under the impression that when weather reporting agencies report barometric pressure, they are actually reporting something that has been normalized for sea level. I live at 8,500ft, so I suspect that if I use some sort of normalized value up here, I'll get poor results from Ballistic FTE.

I have a Kestrel, but I stupidly bought one that did not have a barometer. I do have a Garmin 60CSX, and it does have a barometer. I think it should output the actual pressure, but I'm not certain of that.

Finally, in Ballistics FTE, if I know the actual pressure, should I tell the software my elevation is 0?

 

[Lindy]

Re: A question about how barometric press. is reported

You might find this useful:

Barometric Pressure and Ballistic Software

 

[DaveV]

Re: A question about how barometric press. is reported

Lindy has a great article on the topic here

 

[TimK]

Re: A question about how barometric press. is reported

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">You might find this useful:

Barometric Pressure and Ballistic Software
</div></div>

That was precisely what I needed. It turns out my GPS is outputting barometric pressure, not station pressure. Now that I know, I can use the software appropriately or return my Kestrel and buy the right one.

Thanks!

 

[azimutha]

Re: A question about how barometric press. is reported

I've never paid attention to the altitude or barometric pressure features of the 60CSx. I've always either known my approximate altitude or have been using topo maps that I created myself from DEM-generated contours in ArcGIS. Turns out there is basically no info out there on how well it works or whether it uses/reads out in station pressure or corrected pressure. The manual is worthless in this regard. Guess I will have to fire it up and see what I can figure out. I'm just wondering if it will be worth bothering with.

 

[Lindy]

Re: A question about how barometric press. is reported

As nearly as I can tell from reading the manual, the Garmin 60CSx does not report barometric pressure, but only altitude, which is of almost no use for shooting purposes.

 

[azimutha]

Re: A question about how barometric press. is reported

According to this FAQ section on Garmin's website(http://www8.garmin.com/support/faqs/faq.jsp?faq=131), apparently there is a sensor so you can maybe make some use of it for ballistic calculations. You can do that by going to the Altimeter page and selecting "View Pressure Plot" and then there are a couple other options after that to "Plot Ambient Pressure" or "Plot Barometer". I say maybe because I'm assuming that by sensor they mean an honest-to-goodness sensor, not a calculator. Also, from what I got out of the FAQs the sensor only kicks in when you are using "Plot Ambient Pressure".

Selecting "Plot Ambient Pressure" does appear to be station pressure (25.71), while "Plot Barometer" gives a corrected pressure (29.88). I am at ~4100' and right now the current corrected reading reported for the area is 29.91 at the airport (3935'). Again, my understanding is that the corrected pressure is based off the standard elevation formulas.