Workshop Proceedings - Inter Islamic Network on Space Sciences ...

Theme 1: Country Reports
This approach requires a high resolution satellites images
Spot 5, a systematic sampling scheme as described
previously.
The estimation of area cereal crop is calculated in the site
by the Equation (1) and calculated in province by the
Equation (2)
Sn-1 is the estimated area in the site year (n-1)
Sn the estimated area in the site year (n)
obtained and expressed by the following equation:
•1 is the regression coefficient
• is the origin value
NDVI: Normalized Difference Vegetation Index
Yield : Yields of Durum Wheat, Soft Wheat and Barley
This model uses different parameters by each province
and for each cereal speculation.
Results
Sn-1 is the estimated area in the province year (n-1)
Sn is the estimated area in the province year (n)
Statistical Method Using Spot Vegetation Images
This method (Fig. 4) requires the use of data extracted
from the low resolution images spot vegetation, and the
historical data of cultivated areas by speculation (Durum
Wheat, Soft Wheat and Barley). The objective of this
approach is to adjust the parameters of a statistical model
using the correlation between historical values of NDVI
and historical data of cultivated area for each cereal
speculation to obtain a prediction model described by
the following equation:
In this section we present the results obtained for cereal
area estimation of Wheat and Barley, using three different
approaches described in the methodology. The produced
area estimates are evaluated by comparing the results
obtained with the statistics results of the ministry of
agriculture.
Approach 1
The results obtained, by the approach using the NDVI
threshold per scene SPOT 5 and per date, show a good
correlation between both results with a correlation
coefficient R2 equal to 0.89 for cultivated areas. The
average absolute error is estimated as 18500 ha equivalent
to 15.7 % for cultivated areas (Fig. 5).
•: the regression coefficient
•: the origin value
NDVIi: Normalized Difference Vegetation Index
Cultivated areai: Cultivated area of Durum Wheat, Soft
Wheat and Barley
Fig. (5) Comparison of obtained results by the classification approach
Fig. (2) The steps of the statistical
Cereal yields Estimation
It has been shown in several studies that crop yield is
having high correlation with spectral vegetation index
NDVI. A statistical model by means of a linear regression
between the NDVI historical series and yields data is
Approach 2
The results of cultivated areas obtained with the Mars
approach (Fig. 6) show a poor correlation with the results
of the ministry of agriculture (R2=0.52), especially for the
provinces of Kairouan, Kasserine and Sidi Bouzid.
These three provinces are located in the center of Tunisia.
In this arid area, the cereal crop behavior is different from
other provinces and presents more variability and
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