Suunto X-LANDER Mode D'emploi page 43

1800
2000
2400
2800
3000
3400
3800
4000
4500
5000
5500
6000
Table 1. Normal temperatures corresponding to different altitudes
Now the altitude measurement error caused by an abnormal temperature gradient can be approximated as
follows. If the sum of the temperature offsets from the normal temperatures determined at two different
altitudes is 1 ºC, the altitude difference calculated by Wristop Computer is 0.2% off the real altitude
difference (When using imperial units the offset factor is 0.11% / 1 ºF). This is because the real temperatures
are not always the same as the normal temperatures. A higher than normal temperature causes the calculated
altitude difference to be smaller than the real altitude difference (your mountain ascent was actually higher).
Consequently, a lower than normal temperature causes the calculated altitude difference to be larger than the
real altitude difference (you did not ascend quite as high as displayed).
Table 2 shows an example in which the temperature offsets are positive. In this example, the reference altitude
is set at 1000 m. At 3000 m the altitude difference is 2000 m and Wristop Computer shows 80 m too little (20
ºC * 2000 m * 0.002/ºC = 80 m). Your actual altitude is thus 3080 m.
5906
6562
7874
9187
9843
11155
12468
13124
14765
16405
18046
19686
43
3.3 37.9
2.0 35.6
-0.6 30.9
-3.2 26.2
-4.5 23.9
-7.1 19.2
-9.7 14.5
-11.0 12.2
-14.3
-17.5
-20.8
-24.0 -11.2
6.4
0.5
-5.4