Information and Knowledge Management using ArcGIS ModelBuilder

João Agrela et al.
So modeling becomes directly dependent not so much on the existing technology, but much more on
the user responsible for the model. According to Couclelis (cited by MATOS, 2008) the physical
phenomena may be either atomic or plenum, homogenous or heterogeneous, continuous or
discontinuous, adjacent or disperse, solid or fluid, 2D or 3D, past or actual, static or variable, fixed or
mobile and conventional or self defined. In this human interpretation of the physical characteristics of
phenomena are enough possibilities for error and this classification does not approach ethical or legal
matters. The users have to add and associate to the models the data about variables as dubious as
good and bad and legal and illegal.
Having the above notions in mind it was found by the authors that the discussion about ethics and
methods used in planning per se is, in Portugal, insufficient (LÚCIO et al, 2010). Multiple approaches
for the same problem in different locations allows frequently for different solutions or views (LÚCIO et
al, 2010 in opposition with FONTES et al, 2005). In themselves, both approaches seem sound, but
this ultimately implies that every municipality may have at least one approach for solving the same
problem. There is no measure in Portugal of the funding that is spent financing these solutions, but
one can infer that if there is no degree of centralization in problem solving the waste probably exists
and it probably is not small.
2. The method for modeling using ArcGis Model Builder
The Model Builder application is, in its essence, a set of tools for different purposes. There are many
tools available in the basic ArcGis software, including analysis tools, network tools, data management
tools, etc. These tools operate on raster or vector data. The difference between these two is that
raster data represents reality translating it into a matrix of pixels, each with specific values, and the
vector data simplifies and represents reality in its basic geographic forms (lines, polygons and points).
Each type of data has its advantages and disadvantages, for example raster data allows a full data
coverage of space and because of that it requires a lot of hard disk space, whilst vector data is lighter
but it does not cover space completely. They are used with a simple drag and drop logic and the
chain in which they are arranged is established by the user. If used incorrectly or without some
special notions (for instance, the pixel size must be the same for grid algebra) the outputs will be
wrong. The model design is the vehicle for the human concerns, the order of the operations must be
carefully weighed so that these concerns are encompassed within a logical chain.
Figure 1 displays the basic view of the Model Builder, with all the available tools to the left.
Figure 1: ArcGis Model Builder basic view
The basic layers are displayed in blue, the operations in yellow and the outputs in green. Every
operation must be correctly connected, otherwise the model will simple not run.
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