BMP280 An environmental sensor with temperature, barometric pressure that is the next generation upgrade to the BMP085/BMP180/BMP183. This sensor is great for all sorts of weather sensing and can even be used in both I2C and SPI! This precision sensor is the best low-cost, precision sensing solution for measuring barometric pressure with ±1 hPa absolute accuracy, and temperature with ±1.0°C accuracy. Because pressure changes with altitude, and the pressure measurements are so good, you can also use it as an altimeter with ±1 meter accuracy        Typical application: Enhancement of GPS navigation e.g.time-to-first-fix improvement,dead-reckoning,slope detection Indoor navigation(floor detection,elevator detection) Outdoor navigation,leisure and sports applications Weather forecast Health care application(e.g. sirometry) Vertical velocity indication(e.g. risk/sink speed) Target devices Handsets such as mobile phones ,table PCs,GPS devices Navigation systems Portable health caredevices Home weather stations Flying toys Watches PCB size:(L*W)1.52* 1.20cm/0.60"*0.47"