Indices of structure at the level of the categories / classes of objects

Among the indices of Table 3.1, those of surface and density are already known. Here the description of the other indices.

Index of density of contours (ED):

Σp_ij : sum of perimeters (m) of all the objects j pertaining to category i
A: surface (m²) of the study area

Average index of shape (MSI):

n_i: number of objects of category / class i

Average fractal index (MPFD):

Interpretation: Index value MPFD varies between 1 and 2.
The more complex the average shape of the objects of the class is,
the more its value approaches 2.

A Index of average distance to neighbors of same category/class (MNN):

h_ij: shortest distance (m) between
the limit of the object i and that of the nearest object j of the same category.

Index of dispersion distance to the neighbors of same category/class (NNSD):

Coefficient of variation of the distance to the neighbors of same category/class (NNCV):

4 classes of spatial objects in the study area


Class of objects of poor aptitude (1)	Class of objects of poor aptitude (2)

Class of objects of poor aptitude (3)	Class of objects of poor aptitude (4)

Figure 3.3

Value of the indices of structure for the 4 classes of objects
in the study area illustrated in Figure 3.3

Table 3.3

Exercises on Figure 3.3 and Table 3.3

On Figure 3.3 identify the classes:
- whose surface is respectively smallest, largest
- whose perimeter is respectively smallest, largest
- whose shape is respectively simplest, most complex
- whose average distance between the entities is largest
Compare your visual interpretation with the value of the indices in Table 3.3:
- which are the geometrical properties simplest and most difficult to estimate?
- which is the relation between the value of the average index of shape and that of the average fractal index?