Hokkaido University Preprint Series in Mathematics
We study the visions for contour lines of surfaces when one looks at it from a distant view in some direction. The study of such a landscape (i.e. so-called "topography") is reduced to the study of a certain divergent diagram of the smooth mappings JR. +- M -+ JR.2 , where M is a smooth surface. We give a generic semi-local classification of such divergent diagrams.