Open geospatial data standards and the portability of institutional data

When data is kept in an undocumented format that only a particular piece of software can read, the institution becomes dependent on that software. When a transfer is needed, the geometry can usually be moved, but the attribute structure, relationships between fields, coordinate system information and the descriptions explaining the data's source can be lost. An additional service procurement may be required for conversion, and this work can delay the new system's go-live. The same problem arises when the data needs to be shared with another institution or used in a different analysis tool; every sharing instance turns into a separate conversion job.

Another risk relates to compliance with inter-institutional sharing obligations. The Presidential Decree discussed below requires public institutions to harmonise geospatial data with the specified standards and to submit it to the national platform. Data kept in a closed format also makes fulfilling this obligation more difficult.

Most of the internationally accepted standards for sharing and transferring geospatial data are published by the Open Geospatial Consortium (OGC) and the Internet Engineering Task Force (IETF). The ones most relevant to an institution are as follows:

Each of these standards corresponds to a different need. The specification needs to state separate standards for presenting maps as images, sharing data at the feature level, and delivery as a file.

Presidential Decree No. 49 on Geographic Information Systems was published in the Official Gazette of 7 November 2019, No. 30941. The definition of public institutions and organisations in the Decree also covers municipalities, their affiliated organisations, and provincial special administrations. Article 4 of the Decree sets out, as principles, preventing duplication in the production and sharing of geospatial data, complying with national standards, and ensuring interoperability.

Article 6, meanwhile, assigns public institutions the duty of ensuring that the geospatial data and data information they are responsible for producing are harmonised with and shared in accordance with the specified principles, procedures, bases and standards, and of submitting this data to the National Geographic Information Platform. The Decree defines metadata as "data information."

The Turkish National Geographic Information System (TUCBS) is managed by the General Directorate of Geographic Information Systems of the Ministry of Environment, Urbanisation and Climate Change. TUCBS includes components such as a metadata management portal, the Geospatial Data Sharing Matrix, which determines with whom and in what format data will be shared, a geospatial data dictionary, and an open data portal. Institutions' data services and metadata are displayed through the platform; through the data request portal, services are shared with other users to the extent permitted by the data-owning institution. Benefiting from this system requires an institution's data to be presented through standard services and with complete metadata.

A similar structure has been established in the European Union through INSPIRE Directive 2007/2/EC. The Directive, which entered into force on 15 May 2007, covers 34 spatial data themes needed for environmental policies and contains binding implementing rules for metadata, network services and the interoperability of data sets.

The element of portability most often overlooked is the coordinate reference system. According to the General Directorate of Mapping's definition, Turkey's national datum, TUREF, is based on the ITRF96 frame at epoch 2005.0; older work used the ED50 datum. If it is not documented which datum and projection an institution's data is kept in, which transformation parameters are used between different systems, and how transfer to WGS 84-based formats such as GeoJSON is carried out, positional shifts can appear after transfer.

Metadata explains what the data is, by whom and when it was produced, what area it covers, its quality, and under what conditions it may be used. The basic international standard is ISO 19115-1:2014, which has been updated by amendments published in 2018 and 2020. Even if a data set without metadata is technically transferred, it cannot be used reliably in the new system.

Article 12 of the Public Procurement Law No. 4734 requires that, where they exist, arrangements be made in technical specifications to ensure compliance with national and international technical standards, and prohibits definitions directed at a specific brand or model. Requirements based on open standards are consistent with this provision and secure data portability without narrowing competition. The main provisions that can be included in the specification are as follows:

• That map presentation be provided via the WMS standard, and feature-level data sharing via the WFS or OGC API – Features standards
• That all data be delivered, together with its attributes, in open formats such as GeoPackage or GeoJSON during the contract term and upon its expiry
• That the data's datum and projection information be documented together with the transformation parameters used
• That metadata based on ISO 19115 and compliant with TUCBS metadata requirements be prepared for each data set
• That a data dictionary explaining the data model, field definitions and code lists be delivered
• That, at the acceptance stage, a sample data set be verified by exporting it in an open format and opening it in another piece of software