Expressions make use of the same properties that you can add to label styles, such as Point Level, Northing, and Easting. By using expressions, you can set up separate mathematical formulas using the existing properties. For example, you could subtract a value from a point level, and display that number along side the actual level in a point label.
After you set up expressions, they are available in the Properties list in the Text Component Editor so you can add them to label styles. In effect, expressions become new properties that you can use to compose a label style.
Expressions are unique to a particular label style type. Only those properties that are relevant to the label style type are available to choose from in the Expressions dialog box.
When you insert a property into an expression, it appears in curly brackets if it contains spaces. For example:
{Segment Length}
Do not insert anything else into the curly brackets, and do not remove them. If the property name does not have any spaces (like Northing), then curly brackets are not required.
For expression grouping, use parentheses. For example:
0.567*({Segment Length} + 56)
Expressions are mathematical formulas that are used to compute a value. No text can be added directly to them. Any text you want to include can be added to the label style. For example, to convert feet to meters, you could set up the following expression:
{Segment Length} *.3084
If you want to add “meters” to the end of this string, you must add it later when you set up the label style.