Graeme and Angus McMahon of Sherbrooke Tree Services (Australia) presented a workshop at the ISA Conference in Parramata on a rigging system called Trivect.
The ISA Conference booklet described the system as follows: 'Trivect is a rigging system that uses three, pre-tensioned linesto lower a load. When the load is separated from the tree, the system is designed so that the load remains stationery. This allows for a very high levelof control. Three support lines are considered as vectors and are broken down into horizontal and vertical components, hence the name "Trivect".
As you will see in the video the McMahans use software to calculate the loads. You can download the program they use by visiting the Sherbrooke website.