TerraView
Main Concepts
Project
Project is a
small file (*.tview) that defines the user workspace by
keeping the minimal
information about the layers used. For each layer added to the project,
informations such as: connection info, visual characteristics of line,
point or polygons and Spatial Reference System are serialized in this
file.
Data Source
TerraView supports
different data sources such as:
- Databases: created under PostGIS or Microsoft Access database managment.
- Directory of Files: vector files (shp, kml, etc) or raster files (tiff, jpeg, etc).
Layer
Layer is the representation
of one dataset inside TerraView application. Each layer correspond to
a vector, raster, or tabular dataset stored in one of the datasources available.
- DataSetLayer: This is the
most common type of layer. Layers of this type have one data set that
belongs to a data source and can be a vector or raster data.
- FolderLayer: This
type of
layer is used to facilitate the organization of layers in the 'Layer
Explorer'. A Folderlayer can be expanded to see all layers inside it.
- QueryLayer: This type of
layer is used to create a subset of a DataSetLayer. For example, when a
restriction clause over a dataset is defined, it generates a new dataset that is represented by
this type of layer.
- TabularLayer: This type of layer
is used to show a dataset represented 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
Layer explorer is a tree
structure used to present the layers contained in a project. A
folder layer is an element in this tree with layers inside it. A
context
menu is provided (righ click mouse) to quickly access relevant
operation to each layer type.
Data Table
Data Table is used to present the textual data associated with each layer. Some context
menus are also provided to access the relevant operations in a row, line etc.
Map Display
The Map Display is the area
used to render the selected layers. It can have its own SRID (set or
unset) or by default it takes the first valid SRID among the selected
layers.
Style
The style defines how
a layer should be rendered in the Map Display. For each type of
geometric representation (line, point, polygon) a style can be set. 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 layer to have different visual. The
rule is a filter to be applied to the layer.
- Symbolizers: Structure
that defines how an object should be rendered. Attributes such as fill
color, opacity and others are defined in this element. A symbolizer can also be
represented by an image file or well-known mark.
Style Explorer
Style Explorer displays the style associated
with a layer in a interface where it is possible to add, remove or modify the
symbols that make up the style. A property browser displays all
attributes of a selected symbol and it is modifiable.
SRS / SRID
SRS stands for Spatial
Reference Systems and SRID defines an unique if for a spatial
reference. To correctly render a Layer in a Map Display it
is necessary to have consistent SRIDs (projections) for both the
Map Display and the Layer.
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 different data sources.