I emailed the developer of software and below is their response. Not quite sure if he answered my question or not.
"When absolute is on, it won't adjust for sea level pressure input. With off it will assume the value is sea level. I've found some weather servers return un-adjusted pressure, while others return sea level pressure. If you think the data you're getting in your region is sea level then you want to turn that switch off and let ballistic adjust to your current altitude. This may be the default in the future. What the weather services advertise they send and what actually gets sent appear to be inconsistent. "
Pardon teh spellnig; Sent form my iPhone
On Feb 28, 2013, at 1:36 PM,
I wrote,
I don't have a portable weather device that provides any data other than wind. So I've been using the update button in the top right corner of the HUD settings screen to get this information. When I do this the "Absolute" setting automatically turns on. I was under the impression that I shouldn't be using absolute pressure unless I had a portable unit that could read pressure at my altitude. Should I toggle this back off in this situation?
Thanks,
Scott