Basal anchors
To tie off a line using a basal anchor , pass the rope through a suitable Suspension Point ( SP ) within the crown , then secure the line to an anchor point at the base of the tree , or to the base of another suitable tree .
The line can now be described as having a climbing side ( or end ) and an anchor side ( or end ).
Basal anchor advantages
• The line does not need to be isolated at the SP . The line can pass through several unions and over multiple branches - providing that all parts of the tree ’ s structure with which the rope is in contact are sufficiently strong for the force that is applied there .
• Various basal anchor setups are possible which may allow the rescue climber to be lowered in the event of an emergency , or to be lowered along with the casualty once the casualty has been transferred to the rescuer ’ s system .
Basal anchor disadvantages
• Advancing or adjusting SP may require passing the full length of tail of climbing side through new SP , depending on installation and anchor point type at SP .
• May exert close to 2 x force on SP , depending on rope angles and anchor point type .
• Anchor side of rope and basal anchor are both extremely vulnerable - any impact of dropped branches or cuts will damage the anchor side . Should not be used under suspended or unstable loads .
• Does not ‘ cinch ’ or choke around the target limb . May not be suitable for use if line not set into a branch union ( see image below )
The image on the right shows a system set up with a basal anchor on the left ( red rope ) and a canopy anchor on the right ( blue rope ).
The basal anchor setup does not ‘ cinch ’ onto the target branch , so care must be taken to ensure that the rope is sited securely in a suitable union . Where the rope is sitting over a stub , epicormic shoot or small branch , it may be strong enough to support a test load at ground level but may become dislodged as the rescuer moves through the tree crown .
Canopy anchors choke onto the target limb , so can be installed even on upright stems with no retaining branches .
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