User Manual

Data sheet
BMP085
Page 15
BST-BMP085-DS000-06 | Revision 1.3 | August 2011 Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
3.6 Calculation absolute altitude
With the measured pressure p and the pressure at sea level p
0
e.g. 1013.25hPa, the altitude in
meters can be calculated with the international barometric formula:


















=
5.255
1
0
p
p
-1 * 44330 altitude
Thus, a p
ressure change of ∆p = 1hPa corresponds to 8.43m at sea level
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
30
0
400
500
6
0
0
700
800
900
1
00
0
1
1
00
Barometric pressure [hPa]
Altitude above sea level [m]
Altitude in standard
atmosphere
Figure 4: Calculation absolute altitude
3.7 Calculating pressure at sea level
With the measured pressure p and the absolute altitude the pressure at sea level can be
calculated:
255.5
0
44330
altitude
- 1
p
p






=
Thus, a difference in altitude of ∆altitude = 10m corresponds to 1.2hPa pressure change at sea
level.