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Following some great feedback from various Arborists from around the globe we have chosen to add a new feature into the software that allows users to set a table of TPZ values based on a variety of size ranges. Table formats are used to make the calculation process more human friendly and also to protect younger smaller trees by applying a value that extends the TPZ area around smaller trees relative to large ones. The following example is a table being used in Canada…

Trunk Diameter (DBH)

Minimum Protection Distances Required
City-owned and Private Trees

< 10 cm
10 – 29 cm
30 – 40 cm
41 – 50 cm
51 – 60 cm
61 – 70 cm
71 – 80 cm
81 – 90 cm
91 – 100 cm
> 100 cm

1.2 m
1.8 m
2.4 m
3.0 m
3.6 m
4.2 m
4.8 m
5.4 m
6.0 m
6 cm protection for each 1 cm diameter

ArborCAD will maintain its ability to use the formula driven method and will simply allow users to set up the table driven method as an option. We expect the new table driven software to be made available next week after Easter.