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4
Appendix I Use of Divers at Varying Elevation
Divers can be used at any elevation ranging from 300 meters below sea level to 5,000 meters above
sea level. It is however recommended that all Divers and the Baro-Diver forming part of the same
network be used at the same elevation (whenever possible).
The relationship between atmospheric pressure variations and elevation is exponential, rather than
linear:
P
H
= P
0
· exp[ (M·g·H)/(R·T)]
where
P
H
= atmospheric pressure at elevation height H
P
0
= atmospheric pressure at reference height
M = 28.8 · 10
-3
kg/mol (molecular mass of air)
g = 9.81 m/s
2
(standard gravity)
H = height in meters
R = 8.314 J/mol/K (gas constant)
T = temperature in Kelvin
If the Baro-Diver is placed at a different elevation from the other Divers in a monitoring network, it is
possible for a deviation to occur in the barometrically compensated data due to the relationships
referred to above. The graph below illustrates the deviation in the barometric data as a function of the
variation in elevation at 5
C and 25
C.
To determine the relative barometric pressure deviation relative to P
0
at 5
C (T = 278.15
K) at a height
differential of H, the above referenced formula can be used:
(P
H
- P
0
) / P
0
= 1 exp[ (M·g·H)/(R·T)] × 100%
(5)
By substituting the data, a relative deviation of 1.2 % at a height differential of 100 m is obtained. At a
height differential of 1,000 m this increases to 11.5 %.
We therefore recommend that all Divers and the Baro-Divers in a network be placed such that the
mutual height differentials are minimized.
If necessary, multiple Baro-Divers can be deployed to avoid the abovementioned issues.
0%
5%
10%
15%
20%
25%
30%
0
1000
2000
3000
d
e
v
ia
ti
o
n
[%
]
altitude [m]
5 °C
25 °C
