The BMP180 is a precision sensor from Bosch for measuring barometric pressure and temperature. This change in pressure can also be used to measure change in altitude, and can therefore function as an altimeter.
This sensor is completely identical to its predecessor, the BMP085 in terms of firmware and software that you can use the libraries from BMP085 for BMP180.
Connect the BMP180 to the Arduino as shown below:
Install the Sparkfun BMP180 Library on the Arduino IDE. To do this, go to Sketch -> Libraries -> Library Manager.
Open the sample code by going to File-> Examples -> Sparkfun BMP180 ->SFE_BMP180. Change the value of the variable ALTITUDE according to your local altitude. For example, if you are in Cebu, the altitude value is 17.
Upload the code. Open the Serial Monitor. It should display an output similar to the figure below: