Scale Filter

All graphics in NTF files are tagged by Ordnance Survey with a Feature Code; this is a number indicating the type of feature it represents.

Building outlines have the Feature Code 1, and are generally fairly small items on a map, while Road Centrelines have Feature Code 98 and are key features at almost any screen scale.

To display every Building Outline when looking at 50km² would normally be inappropriate whereas to display Road Centrelines is very useful.

For this reason, Cadcorp SIS Desktop filters out certain features when the screen display scale becomes too small. This is called a Scale Filter.

You can use scale filters for your own graphics by setting the minimum and maximum scale threshold properties of editable items (Minimum scale and Maximum scale).

To change the scale filtering of read-only data like Ordnance Survey NTF then you can either edit the Feature Table or force the scale thresholds using Overlays.

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