57
3. Effective height LAS / XLAS
The accuracy of the fluxes of sensible heat and evaporation depends strongly on the mean height of
the
LAS
above the surface. In case the area is completely flat the average beam height can be easily
derived from the Transmitter height and the Receiver height. In case the area is very complex (such
as shown in Figure 37) it becomes more difficult to determine the
effective
height of the
LAS
/
XLAS
.
The EVATION software has a special tool that helps the user to determine the effective height
(“
Effective height calculator
”). The “effective height calculator” needs the following input data:
transmitter installation height, receiver installation height, the elevation of the transmitter and receiver
site, and the elevation plus position of a number of points along the optical path of the
LAS
(i.e.
EVATION needs a cross section of the
LAS
setup over the area). By entering this information in the
“Effective height calculator” the software gives you the effective height of the
LAS
, which finally will be
used in the actual data processing to fluxes. An example is shown in Table 6 and Figure 37. You can
use the table below for collecting a number of points to determine the effective height of your
LAS
setup.
Distance to
reference
[m]
Elevation
[m]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Summary of Contents for LAS
Page 1: ...Instruction Manual Large Aperture Scintillometer LAS...
Page 28: ...27 Figure 17 Operational weather station of LAS RET system...
Page 29: ...28...
Page 39: ...38...
Page 45: ...44...
Page 49: ...48...
Page 51: ...50 Figure 33 Configuration screen and default settings of supplied RF modems...
Page 55: ...54...
Page 69: ...68...
Page 71: ...70 APPENDIX 9 CONNECTION PLAN LAS BET LAS RET Figure 47 Connection plan LAS BET system...
Page 72: ...71...
Page 73: ...72 Figure 48 Connection plan weather station LAS RET system...
Page 74: ...73 Figure 49 Connection plan scintillometer LAS RET system...
