Want a video tutorial on the Tree Protection Zone? Click below:
Tree Protection Zone will show up in the tree details form, as well as, a symbology layer to view in the map.
TPZ (Tree Protection Zone): This value is determined by the DBH and TPZ ratio (which is determined by the user and is based on the species tolerance, site conditions, and value of the tree). The output is a radius within which construction activities should be avoided (things like operating heavy machinery on the surface, digging, etc.)
CRZ (Critical Root Zone): Also referred to as the SRZ (Structural Root Zone), this value is only needed when major disturbance to a TPZ is needed. This is a smaller radius within the TPZ that is critical to the overall stability of the tree. Calculations again will vary based on region or country. The CRZ ratio is determined by the user and is based on the species tolerance, site conditions, and value of the tree. A tree’s TPZ can’t always be avoided – in the case that it must be breached, it is highly recommended that the CRZ/SRZ be avoided to ensure the stability of the tree.
With TPZ/CRZ Symbology turned on:
The Measure tool can be used to verify the radius.
Note: There is a max resolution to the symbology, so you might need to zoom into the map to see the zones.
Calculations
INVENTORY will default to these equations for calculating TPZ and SRZ. Please contact us if you would like a different formula used in your app.
United States:
Note: The end user determines the TPZ and CRZ ratios based on species tolerance, site conditions, and value of the tree.
Australia & United Kingdom:
If you would like Veteran trees to have a factor of 15 instead of 12, please let support know so they can apply that change for you.
If you would prefer it to be called Root Protection Area (RPA), support can change that too.
Note: TPZ should not be less than 2 m or greater than 15 m. INVENTORY will automatically round to these bounding values.
While the TPZ relies on the DBH for calculation, the SRZ relies on the Diameter at Root Flare (DRF) [m]. See formula below where ‘D’ references the diameter measured at the base of the Tree just above the root buttress.
