Atlas has a variety of features to make geospatial rendering easy. This section provides a brief description of each of them. For more information about the implementation details, refer to Atlas Design.
An entity is any geospatial object that can be rendered in the scene. Atlas supports a variety the following entity types:
|Point||A point is just a point in space. It can be rendered in a variety of ways, such as a small dot or a sprite image.|
|Line||A line (more precisely a line string) is a path between a sequence of points.|
|Network||A network is a collection of connected lines. Networks provide an API for operations over the whole network.|
|Polygon||A polygon is a 2D shape described by a ring of points. Polygons can also be extruded into 3D prisms.|
|Mesh||A mesh is a complex 3D geometry that can provide a more realistic representation of a real-world object.|
An entity represents a geometric form, but a feature represents an object in the real world. A feature contains a collection of entities that can be used to display the feature in different forms. For example, a building can be represented by its centroid (point), footprint (polygon), massing (extruded polygon) or model (mesh).
Atlas provides simple editing functionality for simple entities (i.e. not meshes). In edit mode, the points that make up an entity's geometry will be rendered as handles that can be dragged and dropped to modify the entity's shape. Other operations such as moving, rotating and scaling an entity can be performed in a similar way.
GIS data can be very complex and have many dimensions of information. Atlas provides logic for projections that can render information about entities onto their visual appearance.
- Colour and height projections set the colour or height of an entity based on one of its parameter values relative to the same parameter values of other entities.
- Dynamic projections can animate changes in the colour and height of an entity over time.
The overlay is the area of the browser window that covers the Atlas viewer component. The overlay can be used to display information relating to the contents of the Atlas scene in the browser using standard HTML elements. This is preferable to rendering the same information in the the rendering library's GUI because the code (HTML, CSS and JS) can be reused consistently with any rendering library.
The two primary uses of the overlay are popups and legends.
A popup is a user interface element that hovers over an element in the scene to display additional information about it. These are analogous to the balloons in Google Earth. Since the popup is displayed in native HTML/CSS on the overlay, it can contain any valid HTML, including text, links, images and embedded videos.
A legend is a user interface element that provides additional information about some visual aspect of the scene. Common use cases for legends include:
- Describing the values associated with different colours in projections.
- Displaying an association between building colours and their land use types.
- Providing general geographic information relative to the current state of the camera, such as a scale for distance or a compass to illustrate which direction is north.