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LINE TRACED ON A SURFACE

Lines (or curves) traced on a surface can be classified into three categories:

    - the geometric lines, that only depend on the geometry of the surface:
 
Line  curvature  asymptotic  geodesic  pseudogeodesic  geodesic circle
Definition (see the notations) extreme normal curvature zero normal curvature - normal curvature = curvature of the curve
- minimal length 
normal curvature proportional to the curvature constant geodesic curvature
Differential condition or      

    - the topographic lines, based on a given vertical direction, supported by .
 
Line level slope helix crest, or thalweg
Definition Constant altitude Maximal slope Constant slope  
Differential condition  

    - the gravitational lines, depending on a given gravitational field .
 
Line flow catenary brachistochrone
Definition line followed by a massive point. - shape assumed by a homogeneous wire placed on the surface
- homogeneous line the center of gravity of which has minimal altitude.
 - minimal travel time 
Differential condition where

 
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© Robert FERRÉOL  2018