Open standards for GIS from an utility perspective
Current OGC Standards
OpenGIS Simple Feature Specification (SFS)
OpenGIS Simple Feature Specification defines open interfaces that enable
communications between geospatial systems of simple vector geometries. Systems
compliant to this standard enable disparate systems to communicate geometry, spatial
reference, and feature properties information.
OGC anticipates that virtually all geoprocessing software vendors will incorporate SFS
within their GIS server and client software programs. This will enable all vendors’
software to work with data from other vendors’ systems. Enterprise data is accessible by
any application from any vendor.
Simple Features support geometry types including points, lines, linestrings, curves, and
polygons. Each geometric object is assigned a spatial reference ID, which can be
different from other geometric objects. The API provides rich functionality by including
publishing, storage, access, and operations functions for geometric objects.
SFS has great potential benefits for utility organizations for data sharing and work flow
reorganization. For example, a construction contractor would have the ability to remotely
connect to a utility engineering department’s GIS server via the Internet in order to access
work plans and update as-built features like poles. With SFS the contractor does not
need to use the same software as the utility and can select the software based upon
application needs.
OpenGIS Grid Coverages
While SFS defines standards for geometric objects (vector), the Grid Coverage
Specification provides interoperability between systems that create or use imagery. This
includes remote sensing sources (aerial and satellite imagery), terrain models (digital
elevation model), and raster maps (scanned).
This specification provides interfaces for image access and basic analysis. Software from
different vendors can query each other over the network to access data. The specification
utilizes the GeoTIFF file format, standard grid geometries, and SFS spatial referencing.
Applications of Grid Coverages for utilities include externally-storing data access;
automatically loading the latest satellite imagery from the imagery vendor’s server for a
particular project area; and publishing data, which provides network map raster map
access to facility locating staff.
OpenGIS Coordinate Transformation Services
The Coordinate Transformation services provide a standard way to access geodata stored
in heterogeneous coordinate systems across a network and adjust the map data so that it
will geometrically overlay to the same spatial reference system. This has extended and
replaced the 2D reference system defined as part of the SFS and defines a standard way
to express spatial coordinates for points in 2D, 3D, and 4D (temporal coordinates)
coordinate systems.
The European Petroleum Survey Group (EPSG) maintains a registry of the most common
coordinate reference systems and transformation parameters and was the starting point
for the coordinate transformation specification. The standard includes projections like
Universal Transverse Mercator (UTM) and State Plane, datums like North America
Datum 1983 (NAD83), and units of measure like meters and US Survey Feet.
OpenGIS Geography Markup Language (GML)
GML is an extension of eXtensible Markup Language, defined by the World Wide Web
Consortium (W3). It enables the encoding for transmission and storage of geographic
information and is based upon the simple feature specification geometry types and
models.
While GML is a very flexible solution, it is well positioned as an open data exchange
standard for transmitting small to medium-sized volumes of data. This standard has been
widely adopted by many vendors. GML is limited by design and requires other
specifications to be implemented, including style definition and communications
protocols.
OpenGIS Web Map Server (WMS)
WMS is an interface specification providing uniform access for web clients to maps
rendered by Internet map servers. The specification enables the dynamic construction of
a map as a picture, answers basic questions about the content of the map, and informs
other programs about the maps it can create.
The specification allows web clients and servers to create and display superimposed maplike
information from multiple remote heterogeneous sources. This allows the end user
to query different web map servers based upon their information requirements rather than
access published web maps.
Utilities can use WMS to publish organization specific information like service calls and
combine other public data sources like weather data. This allows the utility to focus on
its data only.
OpenGIS Web Feature Server (WFS)
WFS extends the concept of the Web Map Server from image-based to feature or vector
information. This specification incorporates SFS features and uses GML for
transportation.
Web clients request geodata from web spatial data servers. The WFS servers return
feature sets as GML for the client. This supports dynamic data access to features
including geometry and attributes. Clients can modify rendering styles and views (pan
and zoom) on the queried local features without additional server requests. Feature
manipulation interface is also supported, including create, delete, and update features.
This enables simple data editing and creation through a web client.
WFS provides a richer functionality than WMS and can be used by utilities to support
robust data access (such as rendering wood poles with different symbols than concrete
poles) and simple data modification and creation (such as facility as-built redlines).
Related Open Standards
While the OGC has defined open standards related to GIS, other standards for system
interoperability including the Java environment, XML, and open source Linux operating
systems have also been evolving. The benefits of these open systems include “Write
once, run anywhere”, simplified system architecture, and improved system reliability.
The MultiSpeak Initiative is a group of more than 40 software vendors and consultants,
the Cooperative Research Network (CRN), and National Rural Electric Cooperative
Association (NRECA) that has developed a specification for system interfaces between
utility software applications.
