A Hull is a boundary item that forms an envelope around all your survey items. You can choose to automatically generate two different types of hulls (Convex or Concave). You typically use the Hull tool in order to generate a simple boundary that confines your Project Items within a border; you can then triangulate the selected Project Items as a surface or Triangulated Irregular Network (TIN).


You can also choose to create a Hull Selection that only envelopes your selected items or item or a Hull All for all the survey items in your project, depending on if you have items selected (Hull Selection) or not (Hull All).


Overview


Quick Usage Guide

  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 one of the following options:
    • Convex
    • Concave
  3. Click Hull Selection
  4. A Hull Boundary is created around your Project Items.
    • You can create your surface TIN from the Boundary you automatically created using the Hull tool.


Examples of Hull Types 

  • 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, which makes it convenient for quickly creating a boundary around all of your survey items.

  1. Create points and breaklines on your Image Terrain. 
  2. Use Hull All with the Concave option.
  3. Select the Boundary created by the Hull tool.
  4. Use Triangulate Within to create a surface TIN to the area within the Hull Boundary.



Using Hull Types: Convex vs. Concave

Convex

  • Convex - Think of the convex option of the hull tool as placing all of you survey items in a loose plastic bag.
    • It creates a wide boundary around the selected items.


Concave

  • Concave - Using the concave option is similar to placing 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 you create will fit around 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.


 


Note! The Concave tool is best suited for average-sized datasets or smaller. If you have an extra large dataset (e.g. with tens of thousands of points), you might be better off manually creating your own boundary.



Tips and Tricks

The Hull tool is a great way to avoid the creation of unwanted triangles in your TIN as shown bellow.

  • In the image below on the left: Triangulate All was used for all Project Items, and you can see the large triangles that don't cover the road.
  • In the image below on the right: a Concave Hull was first used to create a tight boundary around the Project Items, after selecting the new boundary, Triangulate Within was used to triangulate the section lines within that boundary.