Catchbook allows you to create dimensions with a single tap. Page scale is set when you edit your first dimension.
These 2 videos provide an overview on how to create and edit dimensions. Scale is set when the only dimension on the page is edited. When there are 2 or more dimensions on the page, editing the dimensions updates the geometry.
Hint: To create dimensions you need to tap the ruler icon in the more "..."
Creating and Deleting dimensions:
Setting scale and changing units. Notice the geometry does not update when changing the dimension from 10 to 25, as it is the only linear dimension on the page the edit changes the scale:
Visit the Catchbook page for more info!