Introduction

The development of any information system should be supported by information technology standards. International, national and industry standards ensure that spatial data is well handled and managed. The process of unification and standardization of both spatial data and the rules of their circulation initiated long ago, in the era of mass use of geographic information systems (GIS) for GIS products and services, and the development of the GIS market. The importance of geo-information standards in geographic information management is highlighted in a relatively recent review of ISO/TC 211 Geographic information/Geomatics, International Hydrographic Organization (IHO) and Open Geospatial Consortium (OGC) [1].

Among the many GIS standards, we specify spatial metadata content standards, being understood as the properties of spatial data that are necessary and sufficient to identify, effectively search, evaluate, and use. The search tool is usually a geoportal. The term geoportal in Russianlanguage scientific literature is understood both as a geoportal for data search in the traditional sense, and a means of web mapping, a tool of their cartographic visualization on the Web. It was suggested, therefore, to distinguish between geoportals for search, search and visualization, and visualization only [2].

Geoportal is a convenient object for analyzing the use of GIS standards. The purpose of the paper is to review and evaluate the current state of development and use of Russian and international standards for the content of spatial metadata, including the creation of inventory mechanisms and effective search for data and services on their geographic metadata as the primary function of spatial data infrastructures (SDIs) and access to them [3].

The problem is particularly urgent in the context of Russia's transition to the digital economy [4], given its reluctance for the full implementation of SDI technologies [5,6].

Historic review

Interest in similar establishment in Russia emerged towards the end of the last century, when in 1998 non-profit Russian GIS Association in its Information Bulletin has organized a wide public discussion of the draft Russian content standard of metadata of electronic maps, developed by the TC 051 of Rosstandart. Text of this draft drew a lot of criticism, both in its substance and in view of the fact that it has completely ignored the experience of developing de facto international standard FGDC-STD-001-1998 [8]. However, the GOST R 51353-99 on "Geoinformatic mapping. Metadata of electronic maps. Composition and content" has been approved and put into effect on January 7, 2000. Its practical applications are still unknown.

The

Domestic experience

More than twenty years of experience in the creation and operation of geoportals and similar network services offers different approaches to metadata management. It is presented in numerous scientific publications, manuals, regulatory and technical documentation, in the multiple "best practice" analyses. The chart (see Table below) contains selected examples of network services with a brief description of the features of editing, validation, and displaying of spatial metadata.

Let's start with the analysis of domestic, relatively modest, experience.

Among the current geoportals, the Institute of Volcanology and Seismology in the Far East Branch of the Russian Academy of Sciences (FEB RAS) is the first to mention. It is organized on the fairly popular and functional GeoNetwork platform, as well as another service by the Pacific Institute of Geography FEB RAS, it is a part of the stack of software products with open source OSGeo software (http://www.osgeo.org) known in dozens of its applications abroad (https://geonetwork-opensource.org). The platform maintains ISO 19115/ISO 19139 and metadata elements of ISO 15836:2009 Information and documentation -The Dublin Core metadata element set, providing metadata editing. Its operational integration of volcanological data has been repeatedly discussed in the scientific periodicals [9,10].

Another "long-lived" service supporting the ISO 19115 metadata description is organized by the Institute of Computational Modeling from the RAS Siberian Branch in Krasnoyarsk, this research team is widely known for its pioneering work among domestic researchers in the web mapping and online web services for various subject areas [11,12]. This service uses MapServer The relatively recent Metalogeny geoportal of the RAS Vernadsky State Geological Museum also supports ISO standards among other spatial data standards, it is equipped with a builtin metadata editor but uses commercial software [13]. Alas, there are not as many services similar to the above mentioned (see Tables 1 and 2), it is eventually worth noting that our chart contains only selected examples, however adequately reflecting the current situation. The last two lines of its first section contains data on two Russian services that cannot be described according to standards, they represent the Komi Republic geoportal and the service for search and visualization of digital maps, spatial data sets and other materials generated by the Federal Spatial Data Fund of the Center of Geodesy, Cartography and SDI.

International and foreign experience

An example of a search engine, and at the same time of a appropriate visualization, can be the geoportal of the INSPIRE European program in the second section of the chart [14]. The need to create spatial metadata by European Union countries was enshrined in law in 2008 [15] The INSPIRE standard features the inclusion of elements from the ISO 19119:2005 Geographic information -Services known as the ISO 19119:2016 after revision. This is primarily due to the wide distribution of geographic services based on the OGC specifications, including WMS, WFS, WCS, WMC, CSW, GAZ, WCTS, etc. Another feature of the INSPIRE profile is the description not only of spatial data sets, but also of their series, if necessary replacing descriptions of individual (with similar properties) products by descriptions of their collections [16,17].

Another international example, the Arctic SDI geoportal, also based on ISO 19115/ISO 19139 standards, is built on the GeoNetwork platform. . A selection of foreign regional and national geoportals is contained, in particular, in Appendix A of the GOST R 58570-2019 "Spatial data infrastructure. Fundamentals". Typically, the search for multiple datasets, series, and related geographic services is supported by the group of ISO 19115 standards.

Conclusions

The health of the geoportal, like any network service, largely depends on the support of international standards. The analysis reveals that effective search for spatial data resources and related geographic services rests on the use of ISO spatial metadata standards. This statement is true of international and foreign geoportals. None of these Russian geoportals use domestic standards of GOST R 57668-2017 and GOST R 57656-2017. It is worth recalling that the development of an analogue of the ISO/TS 19115-3:2016 Geographic information -Metadata -Part 3: XML schema implementation for fundamental concepts under the national standardization plan is not to be launched until 2021. In the future, we should also revise and evaluate how and to what extent all 19 national standards set for TC 394 Geographic information/Geomatics are operationalised.