Tree climbing controlled felling : 

In complete safety, starting from the bottom, with appropriate PPE (ropes, cut-resistant lanyards, etc.). With the help of ropes, clutches, pulleys and sometimes cableways, the tree is cut, starting with the branches, which will all be securely tied and dropped safely to the ground, before starting to cut its trunk.

Controlled with the help of cranes (trucks, construction sites or helicopters) :  

Operators are forced to employ these methods when lacking suitable space or logistical and safety requirements.

Not controlled at height :

Where permitted by space and only where safe ,trees can be cut piece by piece and dropped to the ground without being tied.

At the foot :  

Complete felling by cutting at the foot of the tree where the surrounding area is free of obstacles of any kind. The tree is felled by means of cutting techniques, directional notches, levering, wedges, hoists (manual, electric or motorized).