A core activity of landscape architecture is designing and construction of outdoor space. In addition to that landscape architecture can be considered a matter of epistemology, a way of looking, with the architectonic composition as core of landscape architectonic research and design. An architectural composition can be comprehended by addressing four layers of interest: basic form, corporeal form, visible form and purposive intention. This article argues that GISc offers researchers new possibilities for representing, analysing and modelling landscape architectonic compositions to study its visible form. The visible form derives from the act of perceiving, which is linked with the sequential unfolding of information as our bodies pass through space. We can understand the visible form from the vertical perspective, its conceptual order, and from the horizontal perspective, its perceptual order.
GISc in relation to the conceptual order deals with geometric properties such as shape, symmetry, rhythm, alignment, congruence, and repetition. GISc in relation to the perceptual order considers landscape architectonic compositions as it is encountered by an individual within it, moving through it, making use of GIS-based isovists and viewsheds. This article focuses on the analysis of the relationship between the conceptual and perceptual order of a landscape architectonic composition by measuring visible space, using GIS-based methods and techniques and link the outcomes to the geometric properties of the design. Piazza San Marco (Venice, IT) and Stourhead landscape garden (Wiltshire, UK) are used as examples to showcase some applications.