Present Data in Application Layers¶

This chapter describes how to configure and use presentation rules to visualize data in application layers in Gemini Terrain. With presentation rules, you can define how different object types should be displayed based on their properties.

Presentation Rules¶

You can find the Presentation option to set up presentation rules for application layers in a separate tab in the properties dialog for application layers.

For data in application layers, you link presentation rules to the values for a given property (or to a combination of multiple properties). This means that all objects with the same property will have the same visual presentation on the map.

Object Types and Properties¶

In an application layer, you can have six different object types:

Point
Line
Text
Polygon
Point cloud
Triangle net

Each object type can have many properties, typically theme code (S_FCODE) and object type (OBJTYPE).

Properties for lines in horizontal list field

Horizontal list field with various properties

You can set up presentation rules for all object types.

Presentation rules dialog

Example of presentation rules for lines, linked to property values for S_FCODE.

Methods for Presentation Rules¶

Normally, you use the From-To method. If the presentation rules should apply to a series of values, for example that line themes from 2002 to 2999 should have gray color, you specify both from-value and to-value.

The From-To and Equal methods

From-value and to-value can be the same, or you can omit to-value (in practice the same as the Equal method).

File Structure for Presentation Rules¶

An application layer consists of two files:

*.aly - contains, among other things, the presentation rules
*.gmi - contains the actual data

Storing presentation rules

Data is stored in the gmi file, while presentation rules are stored in the aly file.