Some graphics are designed to be reproduced at a certain size on the final print; they may not correspond to dimensioned objects in the real world such as roads and buildings.
For instance text items on a map should be reasonably sized on the paper print (a few millimetres high). This helps immensely with readability.
For this reason Symbol, Text and Pen sizes are stored in "paper units". Paper units are related to world units using scales.
- Every dataset knows the scale that its items are designed to be drawn in. You can set this scale using the Dataset tab in the Overlays dialog.
- Different datasets in a SIS Workspace Definition (SWD) can have different scales. This allows you to overlay 1:1250 scale maps with 1:10000 scale maps.
When you overlay a dataset in an SWD, you can force the scale of the items in the overlay. This allows the overlay to override the dataset scale.
We do not recommend this because a single item (which is always inside a single dataset) can appear in two different overlays that are forced to different scales.
This means SIS Desktop 9 draws the item twice with different sizes. This can be confusing especially when editing or selecting the item.