IDLnetOGCWCS

IDL Reference Guide: Network Objects

IDLnetOGCWCS

An IDLnetOGCWCS object lets you access a Web Coverage Service (WCS) server that supports the Open Geospatial Consortium (OGC) standards. The OGC is an international group working to develop standards for the exchange of geospatial content and services including specifications for web delivery of data that combines location and geospatial information.

For additional information on IDL's WCS features, see the following sections:

Web Coverage Service (WCS) Overview

Supported OGC WCS Version

Translating a URL into Property Values

Using Callbacks with the IDLnetOGCWCS Object

HTTP Authentication, Security and Encoding

Note
See Feature Support by Operating System for information on which IDL platforms support the IDLnetOGCWCS object.

Note
A sample IDL program included in the IDL distribution provides a generic WCS browser that lets you peruse and request coverages from a remote OGC server. See Sample WCS Browser for details.

Superclasses

None

Creation

See IDLnetOGCWCS::Init.

Properties

Objects of this class have the following properties. See IDLnetOGCWCS Properties for details on individual properties.


AUTHENTICATION	CALLBACK_DATA
CALLBACK_FUNCTION	CAPABILITIES_FILENAME
CONNECT_TIMEOUT	CONTENT_TYPE
COVERAGE_FILENAME	DESCRIBE_COVERAGE_FILENAME
ENCODE	HEADERS
LAST_FILE	PASSWORD
PROXY_AUTHENTICATION	PROXY_HOSTNAME
PROXY_PASSWORD	PROXY_PORT
PROXY_USERNAME	RESPONSE_HEADER
SSL_CERTIFICATE_FILE	SSL_VERIFY_HOST
SSL_VERIFY_PEER	TIMEOUT
URL_HOSTNAME	URL_PATH
URL_PORT	URL_QUERY_PREFIX
URL_QUERY_SUFFIX	URL_SCHEME
USERNAME	VERBOSE
WCS_VERSION

Methods

This class has the following methods:

Examples

See the following methods for examples:

IDLnetOGCWCS::DescribeCoverage

IDLnetOGCWCS::GetCapabilities

IDLnetOGCWCS::GetCoverage

IDLnetOGCWCS::GetCoverageOfferingBriefs

IDLnetOGCWCS::ParseUrl

Sample WCS Browser

The IDL distribution includes a sample program that allows you to enter a working URL to an OGC server and then call GetCapabilities, DescribeCoverage and GetCoverage from within the user interface. You can modify property values and query characteristics to return the desired data. To run the browser program, enter OGC_WCS at the command line. See the browser help for more information.

Tip
You can use the example IDL OGC WCS Browser as a template for creating an application that queries a remote WCS server. This example is located in the IDL_DIR\examples\ogc\wcs directory where IDL_DIR is the directory where you have installed IDL. Running the example lets you parse a known, working URL to an OGC WCS server, and then make GetCapabilities, DescribeCoverage and GetCoverage requests. By default, returned files are written to your application user directory, a subdirectory of your home directory.

Version History


6.4	Introduced

Web Coverage Service (WCS) Overview

A request for coverage data from an OGC WCS server involves three main requests: GetCapabilities, DescribeCoverage, and GetCoverage. The following describes these operations in terms of the IDLnetOGCWCS object:

GetCapabilities — a general query that returns information about what types of requests are allowed and available. This includes service and summary information about data collections that are contained in "coverage offering briefs," which are transmitted in an XML file that is written to disk.

DescribeCoverage — a request that asks for detailed information about one or more specific coverages where each coverage is a data collection. The server returns details about the coverage(s) in an XML file that is written to disk.

GetCoverage — a request for data relating to a specific coverage. The server transmits a copy of the raw data, containing values or properties of a set of geographic locations, in a file that is written to disk.

For details on how to use the IDLnetOGCWCS object properties and methods to request and receive information from an OGC server, see Making OGC WCS Server Requests. Also see Sample WCS Browser for information about the IDL OGC WCS Browser, a sample program included in the IDL distribution.

Additional OGC Web Coverage Service Resources

The Open Geospatial Consortium web site provides complete details on the Web Coverage Service protocol including the WCS specification and schema documents. You may find the following documents helpful if you need additional WCS resources. See OGC web site (www.opengeospatial.org) to search for these and other resource files.

Table 9-1: OGC WCS Reference Documents

Table 9-1: OGC WCS Reference Documents
Document	Description
Specification	OGC Web Coverage Service, Version 1.0.0, Ref# OGC 05-076r6, 2005-10-14
Schema Definition Documents
`wcsCapabilities.xsd`	XML schema definition used by the remote server when creating a GetCapabilities response, which contains one or more coverage offering briefs
`describeCoverage.xsd`	XML schema definition used by the remote server when creating a DescribeCoverage response, which contains one or more coverage offerings
`owsBase.xsd`	XML schema definition containing base types used in the `wcsCapabilities.xsd` and `describeCoverage.xsd`
`values.xsd`	XML schema definition containing base types used in the `wcsCapabilities.xsd` and `describeCoverage.xsd`
`gml4wcs.xsd`	XML schema definition containing GML types used in the `wcsCapabilities.xsd`, `describeCoverage.xsd` and `owsBase.xsd`

Supported OGC WCS Version

This object supports version 1.0.0 of the OGC WCS standard. The IDLnetOGCWCS object conforms to the OGC WCS standard and is designed to communicate with OGC WCS compliant servers.

Note
Since this object is designed as an OGC WCS client, OGC WCS certification is not applicable. Compliance testing and certification is valid only for WCS servers.

IDL Online Help (March 06, 2007)