open layers
DESCRIPTION
Open layers. History. Google Maps Announced on February 2005 Possibility to explore the world OpenLayers First release on June 2006 Open alternative to Google Maps and Bing made by a group of MetaCarta employees. Géoportail 3D. OpenLayers. BayernViewer. BayernViewer 3D. - PowerPoint PPT PresentationTRANSCRIPT
OPEN LAYERS
HistoryGoogle Maps◦ Announced on February 2005◦ Possibility to explore the world
OpenLayers◦ First release on June 2006◦Open alternative to Google Maps and Bing made by a group of MetaCarta
employees
History
2004 20072005
Maps
2006
Yahoo
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Bayern
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OpenL
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What is OpenLayer?◦an API for building web mapping applications◦pure client-side object-oriented JavaScript, using components
from Prototype.js and the Rico library ◦AJAX (Asynchronous JavaScript and XML)◦efficient tiling◦BSD licensed (standard licence for open source software)
The Map….◦The map is the central piece on a web mapping application
and is represented by instances of the OpenLayers.Map class◦The map has some important properties:
projection, resolutions(zoom levels), units, etc◦A map contains one or more layers◦A map can contain one or more controls
The Map….
The Map….
The Map…The map has plenty of methods to deal with:
◦LayersaddLayer(), getLayer(), removeLayer(), ...◦ControlsaddControl(), getControl(), removeControl(), ...◦To move around:zoomTo(), zoomIn(), zoomOut(), pan(), panTo(), ...
The Layers…
◦The concept of Layer allows us to group/classify the elements that must be rendered on the Map
◦All layers inherit from the base class OpenLayers.Layer
The Layers…defines some common properties for all subclasses:
The Layers…We can classify layers in two main categories:◦Raster (for imagery) Raster layers show imagery from different service providers: Google, Bing, a WMS server, OSM, etc
◦Vector (for features)Vector layers allows us to work with features loaded from a data source...A feature is digital representation of something in the real world: city, river, mountain, ...
The Layers…
Raster Layers…
Vector Layers…
The Layers…◦The protocol determines the way a vector layer
communicates with a data source (HTTP,…). It must be an instance of some of the OpenLayers.Protocol subclasses
◦The format determines how features must be read or written. It must be an instance of some of the OpenLayers.Format subclasses
The Layers…When a layer must be drawn:◦The layer calls the protocol so it can load the data◦The protocol communicates with the data source and reads
the data◦The protocol uses the specified format to transform the data
into features and add them to the layer◦The layer delegates to the renderer the task to render
the features◦The renderer draws each feature
The Layers…
OpenLayers differentiates two kinds of layers:
Base layers and Overlays
The Layers…
The Layers…
◦Base layers are mutually exclusive, only one can be shown at a time
◦There can be any number of OverLays◦The isBaseLayer() property inherited from OpenLayers.Layer
determines the kind of the Layer
The Truth About OpenLayer…
◦Most of the JavaScript code we write with OpenLayers is transformed into HTML elements !!!
The Truth About OpenLayer…
The Controls…
◦Controls allows to interact with the Map◦All controls inherits from base class OpenLayers.Control
The Controls…
◦Controls allows to interact with the Map◦All controls inherits from base class OpenLayers.Control◦OpenLayers offers controls for almost any required
action: navigation, zoom, feature selection,feature edition, etc
The Controls…
Here is the output
Another output ( Vector layer )
Thanks for You Attention…