TerraView
Main Concepts
This new version of TerraView
introduces some new concepts. It is important for the new user to have
knowledge of these concepts, making it easier to adapt. Some of these
concepts are:
Project
The project is a physical
file that defines the workspace of a user. All layers created by a user
are serialized in this file. Importantly, the data are not stored in
the project file, but just a link to where the data sources are located.
Data Sources
The terraView supports
different data sources such as:
- Databases: PostGIS, Microsoft Access, SQLite
- Files: Files can either
be vector files as raster files. To support these data types, library
GDAL / OGR are used.
Layers
Layers are the representation
of the data sets in TerraView. Initially there are some types of layers:
- DataSetLayer: This is the
most common type of layer. Layers of this type have one data set that
belongs to a data source.
- FolderLayer: This type of
layer is used to facilitate the organization of layers in the layer
explorer, allowing the grouping of layers.
- QueryLayer: This type of
layer is used to create a subset of a DataSetLayer. Defining a
restriction clause, it generates a new data set that is represented by
this type of layer.
- TabularLayer: This layer
allows you to view data set present in textual files (with well-defined
format) such as CSV, or even binary files of type DBF. These files may
or may not have geometric representations.
Layer Explorer
This component uses a tree
structure to represent the layers contained in a project. A context
menu is provided for quick access operations that are relevant to each
type of layer or sub element of this layer.
Data Table
This component is a table
used to represent the textual data associated with each layer. Context
menus are also provided to access the relevant operations.
Map Display
The map display is the area
to be used to render the selected layer in the layer explorer. This
component defines a geographical reference system to be followed by all
layers to be drawn in this component.
Style
The style defines how
a data set should be rendered in the Map Display. For each type of
geometric representation exists a kind of style to set it. A
style is defined by a set of rules and the rules are composed of
sets of symbolizers.
- Rules: It is possible to define a set of rules within a style,
allowing different parts of the data set may have different visual. The
rule is a filter to be applied to the data set.
- Symbolizers: Structure
that defines how an object should be rendered. Attributes such as fill
color, opacity.. are defined in this element. A symbolizer can also be
represented by the image file or well-known mark.
Style Explorer
Displays the style associated
with a layer. This component is possible to add, remove or modify the
symbols that make up the style. A property browser displays all
attributes of a selected symbol, simply allowing its modification.
SRS / SRID
SRS stands for Spatial
Reference Systems and SRID defines an identifier of a spatial
reference. For a dataset to be rendered correctly in Map Display is
necessary that both the layer and the map display have consistent
projections.
Plugins
Plugins are modules of
TerraView that can easily be associated with or removed from the
application. An example of these plugins are the drivers that support
for different data sources.