Web GIS Technologies A R Dasgupta Honorary Advisor GIS Development

Reference Model for Open Distributed Processing

RM-ODP Viewpoints Viewpoint NameDefinition of RM-ODP Viewpoint EnterpriseFocuses on the purpose, scope and policies for that system. InformationFocuses on the semantics of information and information processing. ComputationalCaptures component and interface details without regard to distribution EngineeringFocuses on the mechanisms and functions required to support distributed interaction between objects in the system. TechnologyFocuses on the choice of technology.

OGC Services Framework OSF ServicesOGC Service Taxonomy Application ServicesGeographic Human Interaction Registry ServicesGeographic Information Management Data ServicesGeographic Information Management Portrayal ServicesGeographic Human Interaction Processing ServicesGeographic Processing Interaction

OGC Services

Realising Services in Web

Services Interoperability Stack

OGC Simple Feature Specification Interface for OpenGIS Simple Features. Designed for tightly coupled applications Spatial and non-spatial properties Two dimensional The supported geometry types include points, lines, linestrings, curves, and polygons. application programming interfaces (APIs) provide for publishing, storage, access, and simple operations on Simple Features. Three profiles CORBA OLE/COM SQL

Geometry Class Hierarchy

Geometry Class Operations

SQL Schema for Feature Tables

Model the Data Design the schema Use an abstract modeling technique such as UML ISO series ISO/TS – Conceptual Schema Language (units of measure, basic types), ISO – Spatial schema (geometry and topology objects), ISO – Rules for application schemas (features), etc. Make sure partners agree to the model

Geography Markup Language (GML)

XML Extensible Markup Language (XML) is means of encoding a document such that its content is separated from its styling A Schema (.xsd) defines the document structure A namespace defines a particular XML vocabulary A style sheet (.xsl) defines how to represent the document The document (.xml), schema and style sheet are all XML documents Scalable Vector Graphics is an XML specification for graphics Resource Description Framework (RDF) Site Summary (RSS) is an XML specification for syndication of news stories An XPath is a means to address a part of a document An XQuery is used to query an XML document Programmers can interface with an XML document using Document Object Model (DOM) or a Simple API for XML (SAX) However XML is NOT a database XML is NOT a programming language

Example of XML and XSD

A Sample Stylesheet

SVG Display in a Browser

Another Information Community’s Schema Highway is: _Pavement thickness _Right of way _Width …. Cell transm. Platform is: _Location _No. of antennas _Elevation …. One Information Community’s Schema Road is: _Width _Lanes _Pavement type …. Cell tower is: _Owner _Height _Licensees …. (an instance of Road in one IC’s schema) Mayberry’s Cell Tower (an instance of Cell Transm. Platform in another IC’s schema) Mayberry Road GML defines a data encoding in XML that allows geographic data and its attributes to be moved between disparate systems GML: Representing Geographic Features

Geographic Data

…and its GML Schema…

…and a GML snippet

Web Services Broad interpretation of Web Services. http (post/get) SOAP Rest (somewhat!) Provide: access to data data transactions access to metadata metadata transactions visualization (maps) data processing Client WSWS XML Request (message) XML Response (optional attachment) General Model

Web Registry Service

WRS Characteristics Support for searching and retrieving inspired by Z39.50 services (search, present) Support for publishing many kinds of (meta)data— more than just data product or service descriptions Employs a general and flexible model (ebRIM) that can accommodate arbitrary information resources Common operations inspired by WFS requests (e.g. transaction) Schema-agnostic—the content of metadata may conform to any schema or Internet media type (e.g. application/xml, application/pdf, audio/mpeg, image/png)

Role of Registry Services Purpose: locate, access, and manage arbitrary metadata in an open, distributed system Registry Interfaces Client (Browser) Service Provider Find Publish Bind service offer type definition service instance A registry is intended to support the retrieval, management and storage of shared metadata information resources

Web Mapping Service (WMS)

OGC Web Mapping Service (WMS) WMS Primary specification for requesting maps and visualization via the WWW. ISO’s WMS draft (Doc ) is based on the OGC WMS specification. Digital Earth Viewer example Digital Earth Viewer Calling client specifies the bounding box of the layers needed, the styles in which these layers are to be displayed, the spatial reference system to be used, the desired output format, the output size, And background transparency and color.

OGC Web Mapping Service (WMS) 3 requests getCapabilities: obtain service level metadata describing service content and acceptable request parameters. getMap: obtain a map image whose geospatial and dimensional parameters are well-defined. getFeatureInfo (optional): ask for information about particular features shown on a map.

CubeWerx WMS CubeWerx Web Mapping Service Web Mapping Server maintained by X. Weather Forecast Data EPSG: / /P1D Clouds Forecast cloud cover Temperature Forecast temperature image/gif image/png image/jpeg <OnlineResource xmlns:xlink= xlink:type="simple“ xlink:href=" /> OGC WMS – Get Capabilities

OGC WMS GetMap Spatial Context Spatial Reference System (EPSG) Corners of map (geographic extent) Image width & height List of “layers” Layer name Symbolization style Return Format GIF | JPEG | WebCGM | SVG, etc. Background info (color, transparency) Exception Type = InImage | Encoded/Parseable

WMS overlay example REQUEST1: VERSION=1.1.0&REQUEST=GetM ap& SRS=EPSG:4326& BBOX= ,24.913,78.794,36.358& WIDTH=560&HEIGHT=350& LAYERS=AVHRR &STYLES=& FORMAT=image/png& EXCEPTIONS=application/vnd.ogc. se_inimage REQUEST2: VERSION=1.1.0&REQUEST=GetMap& SRS=EPSG:4326& BBOX= ,24.913,78.794,36.358& WIDTH=560&HEIGHT=350& LAYERS=BUILTUPA_1M,COASTL_1M, POLBNDL_1M& FORMAT=image/png&STYLES=style1,st yle2,style3& TRANSPARENT=TRUE& EXCEPTIONS=application/vnd.ogc.se_in image

WMS Context Approved specification for describing, in a portable and platform-independent format (XML), a specific grouping of one or more maps from one or more map servers for storage in a repository or for transmission between clients. Think of it as a map “bookmark”

WMS Context document Boston base map Color+Orthos+2001 Color Orthos 2001 MassGIS Color Orthos 2001 EPSG:26986 image/jpeg Class

Web Feature Service (WFS)

WFS Request GetCapabilities Web Feature Service (WFS) Client Opaque Feature Store Web Feature Server WFS WFS Response GetCapabilities CubeWerx WFS CubeWerx Web Feature Service Web Feature Server maintained by X. Roads EPSG:4326

WFS Request DescribeFeature Web Feature Service (WFS) Client Opaque Feature Store Web Feature Server WFS WFS Response DescribeFeatureType <DescribeFeatureType version="1.0.0“ service="WFS" xmlns=" xmlns:ns01=" xmlns:xsi=" ns01:Roads

WFS Request GetFeature Web Feature Service (WFS) Client Opaque Feature Store Web Feature Server WFS WFS Response getFeature <GetFeature version="1.0.0“ service="WFS“ xmlns:myns= myns:PATH myns:LANES myns:PATH 50,40 100,60 <wfs:FeatureCollection 10,10 10,11 10,12 10, ,10 10,11 10,12 2

Filter Encoding Implementation Specification XML encoding of the OGC Common Catalog Query Language (CQL) as a system neutral representation of a query predicate. Can be used by services to query objects from a web- accessible repository. Examples Spatial operators (equals, disjoint, touches, within, overlaps, crosses, intersects, contains, within, beyond, bbox) Comparison operators (propertyIsEqualTo, propertyIsNotEqualTo, propertyIsLessThan, propertyIsGreaterThan, etc) Logical operators (And, Or, Not) Arithmetic operators (Add, Sub, Mul, Div) Copyright 2003 Global Science & Technology, Inc.

Approved OpenGIS ® Specifications Tightly coupled: Simple Feature Access 1.1 – OLE, SQL, CORBA Gridded Coverages 1.0 Focus on Web Services (loosely coupled). Catalog Coordinate Transformation 1.1 Web Map Service (WMS 1.3) Web Feature Service 1.1 Filter 1.1 Geography Markup Language (GML) Style Layer Descriptors 1.0 Web Coverage Service 1.0 Web Map Context 1.0 Location Service Core Specification Set 1.0 Geographic Objects 1.0 GML in JPEG Web Map Context 1.1 OGC Common 1.0

My contact details: A. R. Dasgupta Honorary Advisor, GIS Development and Distinguished Professor, Bhaskaracharya Institute for Space Applications and Geoinformatics, Gandhinagar Fax: +91-(79) Phone: