As seen in the previous chapter, the mathematical modelling for defining geospatial data is based on adopting a reference system through which the data is georeferenced in space. In this case, georeferencing means determining the coordinates of points through mathematical relationships between values of quantities previously known or measured in the field concerning a terrestrial Coordinate Reference System. Thus, considering that the theories about reference systems were presented in Chap. 4 , this chapter presents the theories about Coordinate Reference Systems regarding Geomatics applied to Civil Engineering.