A disconnected component is an island of points that are separated from other islands in the same point object.
Edit > Select > Disconnected Components (applicable to an unordered point object) puts islands of points into “island groups” based on their proximity, then selects island group based on their percentage of the entire object. Use this to select disconnected components for deletion or further processing.
The parameters are:
Separation (medium, low, high) - affects the grouping of disconnected components.
Low - every disconnected component represents an “island group” of one. This setting is usually acceptable because you have the most control of the greatest number of individual disconnected components.
Medium - the disconnected components that are close neighbors of each other are considered to be in “island groups.”
High - the disconnected components that are close or moderately close neighbors of each other are considered to be in “island groups.”
Size field - specifies a percentage of the entire point object. An “island group” becomes selected when it’s percentage of the entire object is less than or equal to this Size. When Size equals 0, no “island group” is selected.
After “island groups” have been selected based on their Size (percentage of the entire object), you can click any individual un-selected island group to add it to the overall selection.
Example: There are three disconnected components, representing 5%, 10%, and 16% of the entire object. The 5% and 10% islands are relatively close to each other. The 16% island stands relatively alone.
If Separation is Low, the 5% island will become selected when Size reaches 5, both the 5% and 10% islands will become selected when Size reaches 10, and the 5% and 10% and 16% islands will become selected when Size reaches 16.
If Separation is Medium, the 5% and 10% islands become an island group (probably, depending on their actual distance). The group becomes selected when Size reaches 15, and the all three islands become selected when Size reaches 16.
If Separation is High, the 5%, 10%, and 16% islands become a single island group (possibly, depending on their actual distance). The group becomes selected when Size reaches 31.