4 in 1 Multifunction Altimeter Barometer W/Compass Thermometer for Outdoor Hiking Camping Item Type: Altimeter Barometer W/Compass Thermometer Material: PlasticMeasuring Range: Height: 0-5000m/0-5468.1yd Air Pressure: 600-1000 HPa Temperature: -30℃-50℃ Resolution: Approx. 20m/21.9yd Size(L x W x H): Approx. 85 x 68 x 28mm/3.3 x 2.7 x 1.1in Dial Diameter: Approx. 60mm/2.4in Storage Conditions: Temperature: -30℃-65℃; Humidity: Less Than 90%The compass and thermometer with small size are mainly for decoration, the sensitivity is limited that not suitable for situations requiring high accuracy. The Physical Principles of Product Design and Application: (1) The air pressure decreases as the altitude increases; (2) The change of air pressure will cause the change of the weather, and this change will be displayed on the dial of this altimeter through a high-accuracy transmission device. This device can accurately measure position altitude (absolute altitude), altitude difference, atmospheric pressure and predict weather changes. Use Introduction:1. Absolute height measurement:  The altimeter should be initialized before use (see the figure for operation), that is, adjust the altimeter number to the actual local altitude. At this time, please note: please refer to the marked altitude on the map (you can also check the local altitude on the Internet, the local meteorological bureau) to calibrate the exact altitude of your location. In addition, changes in air pressure and weather will continue to affect the altitude value, so it is necessary to constantly compare the reference altitude value during climbing or walking. Example: Check from the Meteorological Bureau that the altitude of the starting point A is 200 meters, adjust the altimeter pointer to the scale of 200, and when you reach position B, the dial scale is 1500, then the altitude of point B is 1500 meters. 2. Relative height In the process of climbing or marching, if you need to measure the environmental altitude, please follow the following two steps: (1) Initialize the altimeter at the place of departure, that is, align the pointer with 0 scale; (2) During travel or at the destination, the scale value displayed on the dial is the altitude value relative to the place of departure. Example: Adjust the altimeter to 0 scale at starting point A, and when you reach position B, the dial scale is 1500, which means that B is 1500 meters higher than A.