4. RESULTS & DISCUSSION
Fig. 2 shows the relation between true and inferred LAI for
birch and eucalyptus. Based on the evaluation statistics, only
the results from the spheroid and cuboid inversion are shown.
The spheroid inversion fits best for both tree species. Compared
to the spheroid inversion, the goodness of fit for the
cuboid inversion is only a few percent less for the eucalyptus
trees, but can be up to 25% less for the birch trees. The better
fit with the spheroid expressions was consistent throughout
the whole tree series and indicates that the tree macrostructure
defines which analytical expressions fits best.
Results show that the absolute inferred LAI values can be
significantly wrong. However, the relation between true and
inferred LAI shows a linear trend. Inferred LAI values from
the spheroid inversion show a larger range with respect to true
LAI than the cuboid inversion. Linear regression applied on
the whole tree series showed a minimum R2 value of 0.93
for birch and 0.74 for eucalyptus. After removal of the 100%
pruning value, the minimum R2 value increased to 0.98 for
birch and 0.97 for eucalyptus. Removing the 100% pruning
value is a reasonable assumption because the derivation of
the analytical expressions was based on leaf presence in the