有关NMEA数据的类为
struct CNmeaData
{
CNmeaData ();
void ResetData ();
// Data retrieved from the NMEA sentences.
double lat; // Latitude, in degrees (positive=N, negative=S)
double lon; // Longitude, in degrees (positive=E, negative=W)
double altitude; // Altitude, in feet
double speed; // Speed, in knots






