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2. ACCURACY 
As for GIS, definition of accuracy is based upon the model 
entity-attribute-value: generally three types of accuracy are 
taken into account, spatial, thematic and temporal. 
In the course of implementation of database, data collection 
may assume different features: a homogeneity test may stress 
the different degree of homogenity of collected data, for 
different samples; also a correlation test may suggest possible 
linkages between different attributes. 
When hypotheses of normal distribution of data are supported, 
normal statistic inference is used, otherwise non parametric 
statistic inference has to be used. 
In the last cases a great deal of significance tests alternative to 
parametric ones are available; benefits are the following: 
o it's not necessary to state precise hypotheses a priori 
about statistic behaviour of a certain population; 
o difficulties of computation for filing and processing 
data are limited; 
o their understanding is generally intuitive; 
The following tests, at first conceived for lineage evaluation, 
proved useful to increase the accuracy. 
The first application of test analyzes fortified structures and 
settlements datings and it's possible to notice the homogeneity 
of attribute; in a second application comparing settlements and 
churches datings, an opposite result is sharpened. 
The distribution free test named U (Wilcoxon, Mann, Whitney) 
in the version “fied ranks” is used. The Hy hypothesis is that 
the means of two samples are equal, i.e. the samples are 
homogeneous and originate from the same population; the 
hypothesis is verified through the comparison between the 
standardized normal corresponding to a certain significance 
level and an observation equal to: 
  
  
  
7 = 2 where: 
3 3 
mn S?-S rtj-ti 
ss-p| m T m| Umi(U,U). 
Luca EA 
2 
DU. > un + TE MER VU, + U, = mn 
2 2 2 2 
Sy = m En 
XIII century has been esteemed because this kind of control is 
significant only in a sincronic perspective. 
There are 16 castles (sample A) and 12 ecclesiastic structures 
(sample B) originate during this century. The value is 1 if dating 
is provided exactly (a precision of an year), 2 if dating il less 
precise, moreover values are ordered downstream the value and 
identified with the sanple. 
"t" represent the number of links in next groups in samples A 
and B, while R are ranks of both samples (We remind that rank 
value in case of links is computed giving a growing order to 
common values, adding those values and dividing them for 
number of links. 
In the first case there are 16 values equal to 1 for A, and 10 for 
B, no values equal to 2 for A and 2 values for B. The rank for 
first 26 values equal to 1 is 13.5, while for ther values equal to 2 
is 1,5. The final value for z is 1,66 and thus this value is minor 
to the critic value of standardised normal Z= 1.96 for a 
significance level of a = 0.05, we can say that samples are 
homogeneus. 
An opposite result (z=3.18) is achieved iterating the test for the 
same sample B and another sample C (ecclesiastic structures) 
for whom 17 values equal to 1 and 5 values equal to 2 are 
counted (data refer always to XIII century). 
Results could be read as following: a castle is a power control 
centre of territory and such power is expressed by a foundation 
act (a documentary source is a remembrance for future of such 
act). À settlement foundation is often tied to a castle, while an 
ecclesiastic structure, if it is a simply church, not a monastery, 
has the predominant role to be a social gathering centre, and the 
foundation act is not transmitted to future generations. 
  
Now we propose, as a correlation test, the distribution free test 
of Spearman, in the version “fied ranks”. The Hy hypothesis 
concern the independence of two attributes; here the atrributes 
are the dating and map reference accuracy. If computed value is 
lower than the value issuing from table at a certain level of 
significance, two attributes are not mutual connected. 
where: 
M =1/6(n’n) 
712$ «À =r) 
T, -M12V (6 - 1) 
M-(XD? «T, + Ty) 
WM - 2T, XM - 2T, ) 
Y — 
The ecclesiastic structures group, built during XIII century, is 
entertained: it includes, as above, 22 elements. Regarding 
dating, values are the same of the previous test, while, regarding 
the map reference, a value equal to 1 is assigned to structures 
spotted on maps properly to map's tolerance, a value equal to 2 
39 
for less precise references, and at last the value 3 to unpreserved 
structures that are linked to the aerial centroid of geometric map 
entities. 
Sample values, concerning both attributes, are organized in a 
double row matrix, other two rows include rank of two values 
corresponding to the same element; they are computed in the 
way above described if values appear several times (tied ranks). 
D is the difference in rank between samples. (the sum of D has 
to be equal to 0). 
Regarding dating, values 1 (appearing 17 times) have rank 9, 2 
values (appearing 5 times) have rank 3; regarding map 
references: values 1 (appearing 7 times) have rank 4, 2 values 
(appearing 13 times) have rank 7, 3 values (appearing 2 times) 
have rank 1,5. 
The result r is 0.76, thus it is lower than reference value that is 
the t of Student (t,=1.72 for a=0.05 and v=n-2=20). The starting 
hypothesis is not refusable, so samples are not mutually 
connected 
We expected an opposite result (low level of territory control is 
connected to a low level of searching out).