Added simple barometric formula to MS5611 driver

include/sta/drivers/MS56xx.hpp

@@ -169,6 +169,10 @@ namespace sta
          * @return float The altitude estimate in meters.
          */
         float getAltitudeEstimate();
+
+        static float getSeaLevel(float pressRef, float altRef);
+
+        static float getAltitudeEstimate(float pressure, float sealevel);
     private:
         /**
          * @brief Reset the sensor.