In preparation for heading to the range this afternoon, I was checking the weather forecast and also took a look at the nearby airport 3-day readings, which list station pressure as well as corrected (sea-level or altimeter) pressure. I was struck by how even a difference of 324 feet in altitude affects the station pressure readings between the airport and my calibrated GPS. The airport Wx was reporting 26.37 inches and my GPS 26.13. At the range elevation, the estimated reading will be 24.92 (assuming similar weather conditions).
The point here is that if you use station pressure it should be off a device. Don't take a reading from the airport and apply it to a significantly different elevation. If you can't get a reading onsite, it seems like you'd be best off taking the airport corrected pressure and guesstimate your altitude (or easy enough, carry a topo map). Unless weather is going to be dramatically different at your shooting altitude that would be reliable enough.
As a follow-up to an earlier post, I was speculating at the time whether it made any difference knowing the altitude when calibrating your device. It does.
The point here is that if you use station pressure it should be off a device. Don't take a reading from the airport and apply it to a significantly different elevation. If you can't get a reading onsite, it seems like you'd be best off taking the airport corrected pressure and guesstimate your altitude (or easy enough, carry a topo map). Unless weather is going to be dramatically different at your shooting altitude that would be reliable enough.
As a follow-up to an earlier post, I was speculating at the time whether it made any difference knowing the altitude when calibrating your device. It does.
