It is seldom the case that the trunk of a tree is directly proportional to its spread and, therefore, you should not use a symbol which incorporates a trunk. To achieve the correct size for both trunk and spread, a combination of a symbol representing the canopy and a circle representing the trunk is required.
The Symbol property page should specify the symbol representing the tree canopy. The type can be either a 1-point or 2-point scaled symbol. If you set the type to be a 1-point scaled symbol, you will need to provide a symbol scale dimension or assume a default from the fields. If you set the type to be a 2-point scaled symbol, as shown below, the distance between the two points defines the scale. You would also normally use the option to hide the second point as this will stop any point marker or annotation being displayed there. Some users have set up a series code prefixes for trees with each representing a tree of a given size. Each code prefix has a 1-point scaled symbol enabled and a default value for the spread in the fields. The tree spread is indicated in the code prefix, for instance, TE01, TE02 and so on.
The Shape property page should be configured to display a one-point circle using whichever of the radius, diameter or circumference types that you prefer. This value must be measured and entered into the data logger or taken from a default in the field. If you have specified the canopy type to be a 2-point scaled symbol, the option to display the circle at alternate points should also be enabled so that only one trunk circle is displayed for each tree. In this case, care should be taken when using the option that adjusts the surveyed distances by the radius of the trunk. If you are using a 2-point symbol, there should not be a default for the radius, diameter or circumference dimension, or at least it should be set to 0.0. If there is a default with a value, the offset will be applied to both points and whilst the aim to adjust the trunk point is achieved, the canopy point will also be shifted by the same amount. However, since tree canopies are generally indicative of the size, the error introduced may be acceptable.
When displaying trees, you will often choose to display text. If the Hide Second Point check box is ticked, the text will only be displayed at the first point. The use of macros described earlier in this chapter enables you to display multiple lines including the height, spread, trunk girth and tree species.