Kipp&Zonen LAS MkII Scintillometer - Manual (Page 83)

83
Instruction Manual - LAS MkII Scintillometer
.
The accuracy of the fluxes of sensible heat and evapo-transpiration depend strongly upon the mean height of the LAS MkII
optical beam 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 complex it becomes more difficult to determine the effective height of the beam. The EVATION software has
a special tool for this purpose; the effective height calculator.
The calculator needs the following input data:
• The elevation of the transmitter site
• The installation height of the transmitter above the ground
• The elevation of the receiver site
• The installation height of the receiver above the ground
• The elevation and position of a number of points along the beam (a cross-section over the optical path)
By entering this information into the effective height calculator the software provides the effective height of the LAS MkII beam,
which will be used in the processing of data into fluxes.
Use a table, such as that below, to collect a number of cross-section points. In this case the ‘Reference’ point is ground level at
the transmitter site.
Appendix E. Effective height calculator
Points in optical
path cross-section
Transmitter site, Tx (Reference)
Intermediate point 1
Intermediate point 2
Intermediate point 3
Intermediate point 4
Intermediate point 5
Intermediate point 6
Intermediate point 7
Intermediate point 8
Intermediate point 9
Receiver site, RX 0
0
3
7.5
7.5
20
20
18
18
25
36 0
500
750
1000
2300
3000
3500
3700
4000
4500
4700 (Path Length) 50
30
Elevation with respect to
reference site ground [± m]
Horizontal distance
from reference site [m]
Installation height of
LAS MKII with respect
to the site ground [m]
.
The effective height of the LAS beam can then be calculated as shown below.