Contour Lines using the DTM

Contour lines are lines connecting points of equal elevation. They are useful because they allow to better understand the shape of the land surface (the topography) on a map.

The Elevation Interval of a contour map is the difference in elevation between successive contour lines. Typical values of the Elevation Interval are 100, 50, 25, or 10 meters for areas with large elevation variations (e.g. mountains) and 5, 2, 1, or 0.5 meters for areas with small elevation variations (e.g. flat land). 

 
Information: The contour lines generated using the DTM (Digital Terrain Model) are useful when the area is covered by objects, like buildings. The objects are filtered out for the DTM generation and they do not affect the contour lines based on the DTM.

 

   
DTM                  Contour Lines using the DTM 

 

   
DSM                  Contour Lines using the DSM 
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2 comments

  • Juan daniel Marin solis

    No, tengo 3 años utilizando el PIX4D, pero siempre me encontrado con el problema de los arboles, aun en estos días y que el programa evoluciona enormemente y de buena calidad, sigue tomando como curvas de terreno los arboles a pesar de que pones una infinidad de puntos de control en el terreno, sobre todo en lugares donde la vegentacion es demasiada densa.

  • Daniel (Pix4D)

    Hello Juan,

    In case you have a very vegetated area with many trees covering a large surface where there are not ground points, it is difficult for the software to estimate where the ground is and the contour lines might fail. 

    In order to compute the DTM, If the point cloud classification is available, a terrain mask is computed based on the classified point groups. Only the Ground and Road Surface groups are left untouched, the other groups will be "smoothed". If the vegetation area is very large, the "smoothing" will not be very strong (the software will not interpolate that surface as flat)  and the contour lines might contain some ups and downs.

    Let me know if this explanations is clear.

    Thank you very much.

     

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