What is an SDI?
Table of Contents
‘Spatial Data Infrastructure’ SDI is a set of both technological and non-technological components establishing an intra-organization and inter-organizational network that facilitates access, exchange and sharing of geography-based information held by various producers in order to maximize their production and use. It holds the structure of working practices and relationships among data producers and users that facilitates data sharing and use.
Data, Users, Policies, Technology and Standards are the five components that make wholesome of a dynamic spatial data infrastructure. In this modern era, the continuous development of Spatial Data Infrastructures has been providing a favourable environment for nature and human management. It is now largely expected that SDIs should contribute to broader goals such as economic development, social stability, good governance and sustainable development of the Nation.
Hierarchy of an SDI
The main reason that a hierarchy concept is applied 
here, is that all common properties and reasons for developing a hierarchy structure, are also applicable to the SDIs’ concepts. A lot of countries today are developing SDI at different levels ranging from local to state or provincial, also from the national and regional levels to introduce advancements in the data sector. Some countries are also participating in the creation of a global spatial data infrastructure. These initiatives facilitate better management and utilisation of spatial data assets. The hierarchy of SDI is classified into Global SDI, Regional SDI, National SDI, State SDI, Local SDI and Corporate SDI.
NSDI
National Spatial Data Infrastructure (NSDI) is defined as the technologies, policies and people necessary to promote sharing of geospatial data throughout all levels of government. Throughout the world, many NSDI initiatives have been established and many researchers have studied it from many aspects. for example NGIIP in Nepal, NSDI in India, NSDI in the USA, the SNIG in Portugal, Australia’s ASDI, Malaysia’s NaLIS, and South Africa’s NSIF. Some of the advantages of NSDI are listed below:
- Guarantees the availability of the data to the users from different agencies.
- Prevents duplication in the spatial data by ensuring the data is collected one time.
- Removes the redundancy of the spatial data.
- Increases transparency of governmental works and decision-making.
RSDI
Regional Level SDI is based on the progress of Regional SDI initiatives, the first two regions that have started to develop SDIs at a regional level are the Asia-Pacific and the European region. Permanent Committee on GIS Infrastructure for Asia and the Pacific (PCGIAP) and the European Umbrella Organisation for Geographic Information (EUROGI) have been coordinating with the Asia-Pacific SDI (APSDI) and the European Geographic Information Infrastructure (EGII) which are coordinated by the respectively.
GSDI
Global Level SDI is an ongoing initiative where regional organisations such as EUROGI and PCGIAP are playing an important role in GSDI which has been helping to build compatible SDI capacity around the world.
There are certain requirements to be implemented in order to develop an SDI which would be feasible for all stakeholders. A proper SDI must have a set of distributed geospatial databases which make the spatial data within reach of consumers. Proper metadata of the specific data clearly define the data source and removes misconceptions regarding its accuracy. The data sharing platforms and methods should be defined in order to increase the outreach of developed SDI. It should be made to reach the hands of each data consumer.
Similarly, the system must be designed in such a way that it would be independent of the hardware and operating systems of users, i.e. it needs to be interoperable and must implement all policies and standard guidelines defined by a renowned agency or government. Analysing the rapid development of spatial data and the expansion in the use of digital spatial data, SDI has become an important spatial aspect. In the developmental process for successful SDI in any country, there are many challenges which must be addressed and resolved before and through the implementation of such projects.
What are Standards?
International Organization for Standardization (ISO), ‘A standard is a document established by consensus and approved by a recognized body that provides for common and repeated use, rules, guidelines and characteristics for activities or their results, aimed at the achievement of the optimum degree of order in a given context.’ Standards are responsible for the formation of building blocks for product development by establishing protocols that can be universally adopted. For any business or organization to go smooth and continuous, it must follow specifications, formal standards, and documented practices. Standards have been helping to maximize the compatibility, interoperability, safety and quality of an SDI. Standards help to measure the quality of products and develop market-relevant standards.
In simple words, a standard is a toolbox to implement interoperability. Standards related to Spatial Data Infrastructure (SDI) development and operation can be grouped into three categories:
- Data content standards: Data content standards are used for understanding the contents of different data themes by providing a data model of spatial features, attributes, relationships and data dictionaries.
- Data management standards: Data management standards handle action involving the discovery of data through metadata, spatial referencing of data, collection of data from the field, submission of data by contractors to stakeholders, and tiling of image-based maps.
- Data portrayal standards: Data portrayal standards are used for the visual portrayal of spatial data using cartographic feature symbology.
There are many organizations or authorities that set up the basic requirements for every sort of service-providing firm. The organizations that are responsible for publishing standards for SDI at different levels can be categorized into four types and are described below in brief:
International Organization of Standardization (ISO)
It is defined as a legal, independent and non-government organization which is located in Geneva, Switzerland that sets standards to deal with both geographic and non-geographic information. It is responsible for specifying methods, tools and services for acquiring, processing, analysing, accessing, presenting and transferring geographic information in digital/electronic form between different users, systems and locations. The technical Specifications numbered in the number range starting at 19101 in ISO.
World Wide Web Consortium (W3C)
W3C is responsible for developing protocols and guidelines related to spatial data access including work on Web graphic file formats, XML and metadata. It develops technical specifications and guidelines through a process designed to maximize consensus about the content of a technical report.
Open Geospatial Consortium (OGC)
OGC is an international organization that focuses on specifying interfaces for discovering, accessing and using geographical data. It primarily builds the open standards for geospatial and location-based services.
Three are three types of OGC standards and are OGC Web services (OWS), Sensor Web Enablement (SWE), and Geo-Processing Workflow (GPW) from which OWS services provide access, discovery & encoding of Earth Observation information.
Web Map Service (WMS), Web Feature Service (WFS), Web Coverage Service (WCS), Catalogue Services for the Web (CSW), and Web Processing Service (WPS) are the features provided by OGC web services.
National Standard Organizations
The organizations or the authorities that reside in a specific country to specify the methods and procedures to carry out standardization in the field of digital geographic information and Geomatics as per the possibilities in that country are called National Standard Organizations.
For every SDI activity to grow and flourish, it must be guided by standards which primarily include specifications, formal standards, and documented practices. Geospatial standards are primarily developed by the International Organization for Standardization (ISO) Technical Committee 211 (TC 211) and the Open Geospatial Consortium (OGC).
Metadata- Data About Data
As it is popularly said, ‘Information is the power,’ Metadata can be defined as an information bag that contains the details about data contents, its quality, condition and other data characteristics. It is generally collected during data development and is specially used to describe the summary information of a set of a particular dataset. Similarly, Geospatial metadata refers to the resources which relate spatially to the Earth. It commonly documents geographic digital data such as GIS files, geospatial databases, and earth imagery.
Geospatial metadata provides all the required information about what, how, where and when is the data taken from. It also is highly used to provide data and information that allows the discoverable resources by interested parties who are looking for resources, evaluated, accessed, and understood by activating proper utilization. The levels of metadata based on their usage are classified into three types:
- Discovery metadata: It is used to assess the availability of required data in a platform. It is the minimum amount of information that needs to inquire about the data. It gives the answer to what, why when, where and how questions of geographic data.
- Exploration metadata: It is basically used to check if the dataset contains a sufficient amount of details to create a sensible analysis. After discovery, more detailed data are needed if data are separated into individual data
- Exploitation metadata: It provides the procedures followed to obtain the required data. This provides data reuse, data holding, and data maintenance to the end users and organization including other properties like transfer, load, interpret etc.
Policy decisions based on data can only be defended if the metadata is of good quality. Metadata structures and definitions should be referenced to a standard. They provide support to the data distribution, data management and project management.
- Data Distribution: In the distribution of metadata, Data Discovery, Metadata Publication and Geospatial Data Portals are the three basic elements. Data discovery contains data files which can use to identify, assess, and access available data resources. Metadata is published on the internet by using a website catalogue, web-accessible folder, metadata clearinghouse etc.
- Data Management: Data management includes different activities such as data maintenance and update, data discovery and reuse, data accountability, and data liability. Similarly, data management helps to check the occurrence of data and the significance of data contributing methods which can minimize data redundancy.
- Project Management: Project planning, coordination, monitoring and contract deliverables are the four basic operations supported by project management. It contains information about project design documents and helps to monitor the development status. Metadata records can serve as a project design document and a means to monitor the project.
What are the Metadata Standards?
The set of protocols or guidelines based on which metadata development task is taken forward are called metadata standards. They define the information required by a prospective user to determine the availability, fitness, access and transfer of the set of geospatial data successfully. They also ensure consistency in metadata content and style. To truly enable interoperability, metadata must be widely understood. Users need to understand what metadata needs to be produced and what should be available to understand a resource.
The metadata must be understandable by anyone using it, no matter their language or cultural differences Some of the metadata standards that have been implemented so are: the Content Standard for Digital Geospatial Metadata CSDGM, International Standard ISO 19115, General Metadata Standards ( Dublin core, the Spatial Data Transfer Standard, the Vector Product Format (VPF), Digital Exchange Standards) etc.
In a nutshell, it is recommended to follow the basic guidelines set up by both national and international authorities for the collection and development of metadata. Metadata is information about the data that effectively locates, manages and utilizes the internal and external resources due to which it must be handled with care and to remove fuzziness over data.
