I - FALSE COLOR AERIAL PHOTOGRAPHY »? Proc. Symp. XVI - IUFRO World
congress - Oslo 1976
II - RELATIVE SPECTRAL REFLECTANCE DISTRIBUTION OF SOME FOREST DAMAGED
PLANTS
In our laboratory, we are engaged in measurements of the relative
spectral distribution of reflected energy by oak, birch, beech and
bracken leaves for several sanitary states. We have also tested an
experimental set-up allowing us to do the same measurements on the
trees £n situ,
Summary of the experimental data,
These measurements may be considered as a preliminary test to a
systematic study which can be extended to a lot of samples and for
several altitudes (from 3 to 500m).
In the laboratory we measure the relative spectral distribution
R = £(A) of the reflected energy between 500nm and 900nm of oak,
birch, beech and braken leaves versus :
- the angle of incidence and the angle of measurement
- the gathering date
- the sanitary state determined from the ratio of necrotic spots.
Then we carry out the measurements of the reflected energy for
the same species in situ.
In order to exhibit from the different spectra the most pertinent
parameters, we arbitrary have normalised the spectral distribution
of the reflected eneray to R - 100 for A = 900nm. This allows us
to compare the spectra of several plants even when the reflected
energies are strongly different.
The normalised spectrum shape is practically independent both
of the angles of incidence and of observation provided that they are
lower than 30?.
So, we have been able to compare the spectra which have been
obtained in the laboratory to those obtained in the forest for oak,
birch, beech and bracken leaves.
The experimental data of this preliminary study have given the
following informations :
- For a healthy foliage
a) for.a given plant, the reflectance is practically
constant between 800nm and 900nm.
b) generally, the reflectance for A = 680nm is very weak
(Rego/Roogo < 0/1).
