When producing groundwork designs especially in Bentley software, I noticed people like to produce them with contours and vertical lines or even tadpole-shaped lines instead of simply doing triangulation. Example:
What is the name of the vertical lines?
These appear to be different types of Depression Contour Lines. These lines are typically used on topographic maps to show where the ground slopes down. Sometimes pure contours are hard to read (or impossible) if elevations aren't marked.
This site has some good examples of where they are found on topographic maps.
These same contour line types are also used in other situations just to show slope directly. It doesn't necessarily mean that the surface wasn't triangulated. It is just a helpful display method.
