5. Geometric database: measured features

The surface of a mechanical part is made up of a set of elementary real surfaces delimited by closed boundaries which can take different forms: sharp edges, connections with tangency continuity, angular points, etc. In practice, as it is impossible to measure directly a point belonging exactly to a boundary, each elementary real surface will be measured by a set of points distributed over an area smaller than its theoretical extent, limited by a minimum distance. In practice, as it is impossible to directly measure a point belonging exactly to a boundary, each elementary real surface will be measured by a set of points distributed over an area smaller than its theoretical extent, limited by a minimum distance to the theoretical boundary.

The description of elementary shapes is based on mathematical definitions of surfaces and on the geometric properties of lines...