I'm almost done with an Excel script that parses the log file and creates a logbook entry with destination, waypoints, landings, etc. I'm stumped at determining night landings. I have the part working that determines the time of civil sunrise/sunset based on lat/lon, but the log file appears to store the time of the flight in local time. So I need to convert the local time (as stored) to UTC time, but I have no way of knowing which time zone offset the time was stored in, or if it's stored with DST, etc...
Here's what I need to know:
Is the time based on something I've set (I.E. my home time of Central Standard Time), and therefore I can reliably hardcode an offet with DST considerations, or does it change itself based on the time zone where the GPS is currently traveling? Does it change automatically with DST?
A simple solution would be to have the time stored in the log file as UTC time. Is this possible?
Also, I'd like some advice. As for determining/logging waypoints and landings, how close would you consider "close enough"? It seems like I remember that the published GPS coordinates for airports are not necessarily the center of the airport. So at a larger airport, it's possible that I might land and remain a mile or more from the official lat/lon of the field. So is 2 miles "close enough" to assume I'm at an airport? And what about altitude... Considering GPS inaccuracies, is +/- 100 feet of airport elevation enough to assume a landing was made, and anything beyond (above) that would make it a waypoint? This is a personal project, so "close enough" is good enough for me.