This technique
of interpolation assumes that the influence of the variable being
mapped is reduced according to the distance between the sampling
sites (ESRI, 2011). The mathematical method used by the
IDW interpolator is shown in equation 1, where z is the interpolated
value, n is the number of individuals observed, zi are the values
assigned to observed individuals and di is the distance
between the observed individuals and the interpolated individuals
(Varella and Junior, 2008).
X ¼
Pn
i¼1
1
dp
i
zi
Pn
i¼1
1
dp
i
This method was adopted because it does not estimate values
that are higher or lower than the maxima and minima registered
at the sampling points, which does not occur in methods such as
the kernel method.
The cartographic base was provided by the Cartography Laboratory
of the Department of Geosciences at the Federal University of
Rio de Janeiro (UFRJ, Geocart). The project resulted in—implementation
of an information network for environmental management
of Guanabara Bay based on GIS, which was developed by Brazilian
Institute of Municipal Administration and Brazilian Institute of
Environment and Renewable Resources (IBAM/IBAMA) in 2002. It
consisted of a mosaic of sheets 1:50,000 of the Brazilian Institute
of Geography and Statistics (IBGE) and the Directory of Geographic
Service (DSG). Only the data relating to hydrography and the coast
lines from the information plans developed by this project were
used.