MissionPlanner.Georefimage.EstimateOffset C# (CSharp) Method

        private double EstimateOffset(string logFile, string dirWithImages)
        {
            if (vehicleLocations == null || vehicleLocations.Count <= 0)
                vehicleLocations = readGPSMsgInLog(logFile);

            if (vehicleLocations == null || vehicleLocations.Count <= 0)
                return -1;

            List<string> filelist = new List<string>();
            string[] exts = PHOTO_FILES_FILTER.Split(';');
            foreach (var ext in exts)
            {
                filelist.AddRange(Directory.GetFiles(dirWithImages, ext));
            }

            string[] files = filelist.ToArray();

            if (files == null || files.Length == 0)
                return -1;

            Array.Sort(files, Comparer.DefaultInvariant);

            // First Photo time
            string firstPhoto = files[0];

            DateTime photoTime = getPhotoTime(firstPhoto);

            TXT_outputlog.AppendText("First Picture " + Path.GetFileNameWithoutExtension(firstPhoto) + " with DateTime: " + photoTime.ToString("yyyy:MM:dd HH:mm:ss") + "\n");

            // First GPS Message in Log time
            List<long> times = new List<long>(vehicleLocations.Keys); 
            times.Sort();
            long firstTimeInGPSMsg = times[0];
            DateTime logTime = FromUTCTimeMilliseconds(firstTimeInGPSMsg);

            TXT_outputlog.AppendText("First GPS Log Msg: " + logTime.ToString("yyyy:MM:dd HH:mm:ss") + "\n");

            return (double)(photoTime - logTime).TotalSeconds;
        }