GPS: Do initial zero value publication to avoid corner cases

src/drivers/gps/gps.cpp

@@ -363,7 +363,36 @@ GPS::task_main()
 				/* reset report */
 				memset(&_report_gps_pos, 0, sizeof(_report_gps_pos));
 
-				_Helper->reset_update_rates();
+				if (_mode == GPS_DRIVER_MODE_UBX) {
+					/* Publish initial report that we have access to a GPS,
+					 * but set all critical state fields to indicate we have
+					 * no valid position lock
+					 */
+
+					_report_gps_pos.timestamp_time = hrt_absolute_time();
+
+					/* reset the timestamps for data, because we have no data yet */
+					_report_gps_pos.timestamp_position = 0;
+					_report_gps_pos.timestamp_variance = 0;
+					_report_gps_pos.timestamp_velocity = 0;
+
+					/* set a massive variance */
+					_report_gps_pos.eph = 10000.0f;
+					_report_gps_pos.epv = 10000.0f;
+					_report_gps_pos.fix_type = 0;
+
+					if (!(_pub_blocked)) {
+						if (_report_gps_pos_pub != nullptr) {
+							orb_publish(ORB_ID(vehicle_gps_position), _report_gps_pos_pub, &_report_gps_pos);
+
+						} else {
+							_report_gps_pos_pub = orb_advertise(ORB_ID(vehicle_gps_position), &_report_gps_pos);
+						}
+					}
+
+					/* GPS is obviously detected successfully, reset statistics */
+					_Helper->reset_update_rates();
+				}
 
 				int helper_ret;