The purpose of this study is to compare the grid usage that is common to Leonardo da Vinci and
J.N.L. Durand in the process of designing the architectural plan. In the days when there was no proper measurement tool, auxiliary lines relied entirely on the architect's personal mindset and design convenience.
Therefore, it is considered that studying the auxiliary lines drawn by the architects will be useful for
studying the human perception system. Among auxiliary lines, the grid has been used by many architects.
Leonardo da Vinci and J.N.L. Durand are famous. However, these two show a significant different grid
usage. As auxiliary grid and space ares added the center of the Leonardo da Vinci grid continues to move,
and the grid in his sketch is becoming a building space itself. So I call it 'conceptual grid'. In the case
of J.N.L. Durand, the one center of the grid is always at the center of the drawing. That is, all the
positions of the grid can be determined in phase around a common point, and all of the same
specifications are assumed. The grid is a kind of filter. That's why his grid is a visual abstraction of the
process of thinking. In this paper, I will call the grid of J.N.L. Durand as 'abstract grid'.