Applicable plans
Valley Mountain Peak


A hull is a boundary item that forms an envelope around all your survey items. You can generate different kinds of hulls automatically (convex/concave). You typically generate a hull in order to have a clean boundary that confines your triangulation within a border.


You can create a hull for your selection only or for all the survey items in your project depending on if you have items selected (Hull Selection) or not (Hull All).


Hull Selection

  1. Select the survey item(s) to be included in the operation,
  2. From the HOME Tab, set the Hull Type from the Hull Group to
    • Convex
    • Concave
  3. Click Hull Selection
  4. The hull will be created.


Example


In the image below: 

  • the blue boundary was created with the Convex option selected,
  • the yellow boundary was created by using the Concave option.




Hull All


The hull tool changes to Hull All when nothing is selected in your project. This is convenient for creating  a boundary around all of your survey items.

  • In the image below on the left, I created points and breaklines. 
  • I used Hull All with the Concave option, 
  • Selected the boundary created by the hull tool, and 
  • then used Triangulate Within to limit my triangles to the area within the hull boundary.



Convex or Concave?

  • Convex - Think of the convex option of the hull tool as placing all of you survey items in a loose plastic bag.



  • Concave - Using the concave option is similar to placing the items in a plastic bag and vacuum sealing the bag
    • When Concave is selected, the Sharpness option becomes visible. 
      • This value (1-10) controls how tight the boundary created will fit your survey items. 
      • Think of the value as controlling the vacuum on your bag sealer. The higher the value the more suction and the tighter the fit. 
      • The sharpness value was set to a value of 2 on the left image and a value of 10 on the right image.



Helpful Hint:


The hull tool is a great way to control limit the creation of unwanted triangles in your TIN as shown bellow.

  • In the image on the left, I used Triangulate All and you see the large triangles that don't cover the road,
  • In the image on the right, I create a concave hull first and triangulated the section lines within that boundary (Triangulate Within).