More About Creating Dimensions along a Reference Direction

In the case of a dimension along or perpendicular to a direction, if you delete the linear element used as the reference direction, the dimension will be automatically converted into a dimension along a fixed angle in view (the angle being that of the reference element in the view before its deletion).
The behavior of a dimension along or perpendicular to a direction will actually depend on whether the Only create non-associative dimensions option is activated in Tools > Options > Mechanical > Drafting > Dimension tab, Associativity on 3D button:
- If it is activated, then the dimension will actually be a dimension along a fixed angle in the view (the angle being that of the reference element in the view).
- If it is not activated, then the dimension will always match the direction of the element defining the reference direction.
Once a dimension along a reference direction has been created, you cannot modify the elements that define the direction of measure, i.e. either the linear element used as the reference direction or the fixed angle in view.
The reference direction will not be taken into account when re-routing dimensions (Re-route Dimension command).
Dimensions along a reference direction cannot be driving dimensions. So, if the Create driving dimension option is activated in Tools > Options > Mechanical > Drafting > Dimension tab, you will not be able to drive dimensions when dimensioning along a direction.
Dimensions created in a shot (i.e. cumulated/stacked dimensions, or dimensions sharing the same type as the first one) all have the same reference direction.