The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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The other parameter which was used to evaluate the test results 
is critical difference (CD) to the reference value. This value is a 
value less than or equal to which the absolute difference 
between particular observation and reference data is expected to 
be at the 95% of confidence (ISO 5725). The critical difference 
as comparison with reference value for more than one operator 
can be calculated as below (3): 
(eq. 3) 
Where p = no of operators 
n = no of observations 
a R = standard deviation under reproducibility 
conditions 
o r = standard deviation under repeatability conditions 
3. MEASUREMENT 
The test site was situated on the region of Maussane in France 
and covered 10km by 10km area. All data, i.e. stereo pair of 
Cartosat-1 Aft and Fore and digital orthophoto UltraCamD, 
were projected in UTM 31N (WGS 1984). The set of parcels 
(as polygons) was acquired using ARCGIS software as the 
measuring environment. 
The number of parcels to be measured was probabilistically 
determined according to previous results (Pluto-Kossakowska et 
al., 2007). After field verification (Feb 2008), 203 parcels were 
digitised on UltracamD RGB composition, then verified and 
corrected by independent operator. This set of parcels was 
checked also on Cartosat-1 images, and 18 parcels were 
rejected in terms of invisible borders. This means that only 8% 
of 203 parcels were not detectable on Cartosat-1. Finally, 185 
parcels were used for the study. The land cover classes and 
parcel borders were precisely identified on these selected 
parcels during the field campaign in February 2008. 
Three replicates per parcel were obtained from five operators on 
two images of Cartosat-1 (Aft and Fore) and on the UltraCamD 
orthophoto. The parcels appeared on the screen randomly and 
were enlarged at the maximum zoom within the viewer window. 
On screen, the parcel to be measured was centrally identified 
(see figure 1). After the parcels measurement, the area and 
perimeter were calculated for each observation. The buffer 
value was derived using equation (1) and was used for 
following statistical analysis. 
4. STATISTICAL ANALYSIS AND RESULTS 
4.1 Outliers 
The workflow included a statistical detection of outliers, a great 
variety of which are available from the literature and which 
could be used in this experiment. Using the Jacknife distances 
test, 81 observations out of 4995 (1.6%) were identified as 
significant. SLS procedures allowed the identification of the 
factors and related interactions responsible of the outliers’ 
population distinction ((F(6;80)=30.51 p-value<0.0001, 
^=0.71). The maximum value of the outliers was 61,2m while 
the minimum value was -79,2m. 
The majority of the outlying observations occurred once per 
parcel. Less frequent were the parcels several times with 
multiple outliers: these concerned essentially the three 
replicates from the same operator (and the same image). Even if 
existing, it was very rare that the same image was identified as 
an outlier by several operators from several images. To 
illustrate this specific case, an example is given in Figure 1. 
Figure 1.Example of outliers: 1 on Cartosat Aft, 6 on Cartosat 
Fore, none on orthophoto 
The two main groups of factors explaining outliers were (i) the 
“parcel#image properties” defined as the visual representation