Urban Engineering: Concepts and Challenges

3.2 The urban space
One key aspect worthy of consideration is the relationship between the urban engineer and
his territorial preserve – which amounts in reality to the entire "urban space". This particular
space is not merely an area of land distinguishable from the "rural space" around the city
but also a political space which also provides a home for members of the workforce
(Castells, 1983).
However we believe that the urban and rural territorial spaces are in fact closely integrated
and cannot be viewed as totally independent entities. In an urban engineering context it is
thus vital to employ the ‘systemic’ approach in an effort to understand the mutually
dependent relationship between the city and the surrounding country areas (and vice
versa).
We also need to remember that any definition of what exactly is "urban space" tends to be
fairly arbitrary. In Brazil, areas defined in municipal law (based upon the National Taxation
Code) are considered to be ‘urban areas’. The National Taxation Code defines those areas
which can be considered as ‘urban’. This definition is directly related to the IPTU (urban
property rates) revenue. It is not necessary for these areas to be occupied by a minimum
number of inhabitants or to possess a minimum population density. Other criteria have of
course been adopted in other countries according to their homegrown political, geographic
or cultural circumstances (Jenkins et al., 2007)
In the United States, for example, an area is considered to be "urban" when it has a
minimum of 2,500 inhabitants, with a minimum population density of 1,000 persons other
per square mile (386 persons per km
2
(one square mile = approx. 2.59km
2
)). This figure is
similar to that applying to Canada, where a minimum of 1,000 persons per 4 km
2
is the
norm. In Mexico an urban space requires at least 2,500 inhabitants but no density
requirement. On the other hand, in Peru any area demarcated formally as "urban" has to
possess 
in situ
at least 100 dwelling units.
According to Veiga (2002) if the criteria of population size were combined with local and
demographic density, the urban part of Brazil would represent 57% of the total population
of the country (in 2,000) - not 81.2%, as stated by the Brazilian Statistics Institute IBGE.