What is Generalisation?

Generalisation is the process of making a mapping database legible over a range of viewing scales.

Cadcorp SIS Desktop has several generalising features that make the displayed graphics legible. Since all redraws are generated from the database (and NOT a display list), these generalisation techniques are automatically used as you pan and zoom to give you fast clear graphics.

1. Greeking

When Text items and Insert items are too small to be read they are shown as a dotted line or rectangle.

TIP: See also Labels topic for more details of "Greeking".

2. Skipping Vertices

When you zoom out a LineString item containing many vertices, the vertices can be so close together to be literally on top of each other. 

Cadcorp SIS Desktop will automatically skip over vertices that are too close to each other to be distinguished.

You may notice this with LineString item grab handles - not all grab handles are shown until you zoom in. You can always step through all vertex grab handles using the Tab and Shift-Tab keys.

3. Item Scale thresholds

Every Item can remember a scale range within which it is visible. Many feature codes set these scale thresholds automatically. If you zoom in or out beyond the scale range of an Item, then Cadcorp SIS Desktop will not draw the Item.

4. Overlay Scale thresholds

Each Overlay can remember a scale range within which it is visible. (Notice that this is different from the Dataset reproduction scale.) The Overlay scale threshold overrides the Item scale thresholds.

5. Symbol and Pen simplification

If a Symbol is too small to see in detail, or a Pen definition has dot and dash lengths that are too small to see fully, then they are simplified, possibly down to a single dot or a thin continuous line.

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