guys i want to make wearable device which have provision of stairs steps count. i have LPS25HB (pressure sensor), LSM6DS3 (accelerometer) pressure sensor give the altimeter and accelerometer give the steps count. but my pressure sensor is one type barometer and its value changed according to atmospheric pressure.values variation 3~5 feets from reading of pressure sensor.
All you are interested in is relative change in altitude. The absolute altitude is irrelevant - though you could get that by augmenting the data with GPS.
You cannot of course distinguish perhaps between stairs and a steep hill, but from a fitness monitoring point of view that too is perhaps irrelevant; "work done" (i.e calories burned) is simply a function of the steps taken and altitude gained.
Because local atmospheric pressure changes with weather conditions and temperature as well as altitude an air pressure sensor cannot be an accurate source of absolute altitude without calibration to some known reference under the prevailing conditions.