There is evidently at least one serious misconception in the code that calculates atmospheric pressure, altimeter settings, et cetera. This can be easily demonstrated:
Park at or near the threshold of runway 33 at Aspen (KASE). Under standard conditions, observe that the altimeter reads 7820 feet MSL, as it should. Use the Weather : Weather Conditions dialog popup to look at the ground-level altimeter setting (QNH). This is bottom row in the "Alt (inHg)" column of the popup. Verify that it is 29.92. Now use the dialog box to change this property. Change it to 30.92, a one-inch difference. Go to your altimeter instrument and enter the new altimeter setting in the Kollsman window. Ideally, this should cause the instrument to read the correct altitude once again, namely 7820 feet MSL. However, due to bugs, it is likely that you will observe something closer to 8120. This means the airplane is 300 feet lower than the altimeter says it is. In case it wasn't obvious, when flying around near Aspen, being 300 feet lower than you think you are can be very bad for your health. The absolutely correct formula for computing the altimeter setting can be found in the jsd barometry page -- look where it mentions Field Pressure. http://www.av8n.com/physics/barometry.html While we're in the vicinity: Both the Weather Conditions popup and the atis.cxx code rely on the "pressure-sea-level-inhg" property and use it in ways that the altimeter setting should be used. This is at least a misnomer, and probably a misconception. The altimeter setting is not the same thing as the sea-level pressure. The altimeter setting is something else; it is properly called the altimeter setting. It is also properly called the QNH, although private pilots who fly only in the US may be unfamiliar with the QNH terminology. This property needs to be expunged and replaced with something else, something with a correct name and with correct semantics. ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
