MissionPlanner.ElevationProfile.getSRTMAltPath C# (CSharp) Method

        List<PointLatLngAlt> getSRTMAltPath(List<PointLatLngAlt> list)
        {
            List<PointLatLngAlt> answer = new List<PointLatLngAlt>();

            PointLatLngAlt last = null;

            double disttotal = 0;

            foreach (PointLatLngAlt loc in list)
            {
                if (loc == null)
                    continue;

                if (last == null)
                {
                    last = loc;
                    continue;
                }

                double dist = last.GetDistance(loc);

                int points = (int) (dist/10) + 1;

                double deltalat = (last.Lat - loc.Lat);
                double deltalng = (last.Lng - loc.Lng);

                double steplat = deltalat/points;
                double steplng = deltalng/points;

                PointLatLngAlt lastpnt = last;

                for (int a = 0; a <= points; a++)
                {
                    double lat = last.Lat - steplat*a;
                    double lng = last.Lng - steplng*a;

                    var newpoint = new PointLatLngAlt(lat, lng, srtm.getAltitude(lat, lng).alt, "");

                    double subdist = lastpnt.GetDistance(newpoint);

                    disttotal += subdist;

                    // srtm alts
                    list3.Add(disttotal, newpoint.Alt/CurrentState.multiplierdist);

                    // terrain alt
                    list4terrain.Add(disttotal, (newpoint.Alt - homealt + loc.Alt)/CurrentState.multiplierdist);

                    lastpnt = newpoint;
                }

                answer.Add(new PointLatLngAlt(loc.Lat, loc.Lng, srtm.getAltitude(loc.Lat, loc.Lng).alt, ""));

                last = loc;
            }

            return answer;
        }