I figure about 5,500' MSL for the North Site and 4,800' MSL for the Atlas site. Can't help you on the average barometric pressure...

I've always used about 5300 for both. I'll have to haul the GPS out next launch and get some numbers.

I used topo maps... actually a lot more accurate (typically) than the altitude component of GPS.

I was truly surprised to see the N site at 5,500'. It is definitely higher than Atlas. I can dig out the topos sometime again, but 5,500' and 4,800' are quite close IIRC.

JW

Yeah - the GPS would only be an estimate (accurate to 20 or 30 feet).

My GPS repeatedly reports 5430' at the Pawneee North Site.

Warren

Thanks Guys

Within 20-30 ft is fine it is just for simulations, so it really is pretty close to a mile high.
All the weather sites show a pressure of 30 something inches of mercury. I'm a little skeptical.

CJ Jones

I remember hearing 29.92 inches last oktoberfest. Not sure how representative that is though...

Atmospheric pressure will vary greatly day to day and over time. I don't know that anywhere on earth that has any particular "average" atmospheric pressure.

I'm assuming this info was for simulation purposes? I use Rocksim V4.0, which has no way to set atmospheric pressure. RH (relative humidity) yes, but atmospheric pressure, no...

My GPS logged in 8810 from a road nearby the Hartsel site, which is pegged as 8820. DEAD accurate beyond any altimeter readings, will check both North and atlas now that i know the tech works(from an open range to 4 or more sats, mtn climbers take your baro units.)
J

I have two GPS units... "Old reliable" and a new one that I was given for Christmas. They often read different elevations for the same waypoint. Further to that, the elevations on both will "float" quite a bit.

I had once read that the X axis and Y axis were accurate to w/in a few meters, buy the Y axis was highly variant. As such, I"ve never paid much attention to the elevation component of my GPS....

We had researched the MSL of the two launch sites for the last website, and the 4,800' and 5,500' sticks in my mind. Unfortunately, we weren't able to get all the old info off the old website.

When cranking all of that into the simulations, we often overlook temps. At Hartsel, I actually looked at a thermometer when I launched... it said 49 degrees. Yet when I asked folks around me what they thought the temps were, the lowest guess was 60, with some folks guessing 75. To be honest with you, it felt warmer than 49. My point is that a temp error of 10-15 degrees shifts your sims a lot more than going from 4,800' to 5,000'...

John,

All depends, if using higher precision GPS with a good view of 4 sats that are divergent in the sky, the z uncertainty is at most 1.5 times the x,y position. I believe some of the higher end handhelds now provide sat position data, so you can factor that in to figure the reliability of the Z data. Certainly at high alts, say over 30K, I'd be more inclined to believe GPS data than baro provided you had access to 4 sats--at least that reported from the average altimeter. This issue came up on a THPRA thread and also recently on altimeters here. There are ways to download the data and massage it more fully to increase the accuracy of the baro based altimeter report. But hey whose gonna believe it when you return the next day to report that after data analysis, it flew 1000' higher than reported. 😉

Also besides temp, humidity is a neglected factor, short of rainfall or fog, humidity is a friend, and lightens air in molar proportion. The "ideal" day would be an average summer day in NYC ( 95/95) transported to the Rockies.
John S