Standardization of Metadata of Analog Cadastral Documents Resulting from Systematic Cadaster Establishment

Abstract

The systematic approach to the establishment of a cadaster in most European countries has resulted in a variety of cadastral documents. Most official cadastral data are from the 19th and 20th centuries and are stored as hard copies or electronic data in a data warehouse, while the original documents are stored in analog format in separate locations, making the cadastral data difficult to access. The increasing interest in the use of archival cadastral documents has stimulated their digitalization in most countries, allowing users to access cadastral documents through metadata catalogs. Most catalogs use archival metadata standards to describe cadastral documents, with a lack of application of geoinformation metadata standards that represent fundamental spatial datasets. Archival metadata standards do not provide enough information about the origin and quality of cadastral data. The aim of this study was to examine the applicability of the ISO 19115-1 standard for describing cadastral documents. The methodology includes a comparison and an analysis of documents which are stored in different locations. The metadata of archived cadastral documents are recorded in archive inventories, and archives use different terminology for documents with the same content. The scientific contribution of this study is given by the classification of key documents and their associated properties that uniquely described each document. Four types of documents were classified by comparison, and we analyzed the content between documents. Property identification resulted in the semantic mapping to metadata elements of ISO 19115-1 and showed a considerable congruence of elements. It was possible to apply the ISO 19115-1 standard for describing documents of systematic cadaster establishment, with additional extensions for some elements. Proposed extensions to describe the cadastral documents include replacing free text with domains of appropriate values, adding stricter obligations, and restricting the use of domain values. The standardization of metadata for analog cadastral documents in archives has created a prerequisite for the development of a metadata catalog, which would increase the availability and accessibility of cadastral data for different user groups.

1. Introduction

From ancient times, various types of land information have been collected, recorded, maintained, and used, and cadasters have been established for managing such information. A cadaster is normally a parcel-based, up-to-date land information system containing a record of interests in land (e.g., rights, restrictions, and responsibilities) [1]. It may be established for fiscal purposes and/or legal purposes to assist in the management of land and land use and enables sustainable development and environmental protection [2]. Because of the complexity of the processes of creating a cadaster, it is often called the cadastral system, which is shaped by social, political, and economic conditions, such as by legal and technological factors [3].

There are two approaches to the establishment of cadastral records: systematic and sporadic [4]. The systematic approach has been applied in most European countries, where the purpose of establishment has been primarily fiscal [5,6,7,8,9], as well as in Turkey [10], Japan [11], and the Philippines [12]. A cadaster is established through a cadastral survey project for one designated area, namely the cadastral municipality [8], resulting in a variety of cadastral documents, including spatial representations such as cadastral maps, lists, and other documents. A cadastral map is usually stored in the state archives, popularly called map archives [13,14], while other documents are maintained in cadastral offices before finally being stored in the archives. A large number of cadastral documents are stored in analog format and located in separate places [15]. This sporadic approach has been applied in England, Ireland, Nigeria, some Canadian provinces (the English Group of the cadastral system), Australia, New Zealand, some provinces of Canada, Morrocco, Tunisia, and Syria (the Torrens Group of the cadastral system) [16]. A cadaster is established through a cadastral survey project, and cadastral documentation is created for one possession in the sporadic approach. This research is focused on analog cadastral documentation resulting from a systematic approach of cadaster establishment.

Technological development has resulted in the implementation of computers in the processing of cadastral data and, consequently, the intensive renewal of cadastral documents by digitalization in most European countries, so that today, cadastral maps are available in an electronic form [17]. The vast majority of official cadastral data are from the 19th and 20th centuries and are stored as copies or electronic data in a data warehouse, while the original documents stored in the archives [8]. Although the availability and usage of cadastral data have become faster and simpler, much useful information from analog documentation in archives is unavailable; it is very important to give information about the quality of the dataset, for which metadata are very helpful. Metadata are structural parts of information that describe, identify, and make it easier to use and implement sources of data [18], and they can be stored in storage, catalogs, websites, files, etc. [19].

There is often a need for analog cadastral documents that are stored in various locations, making them difficult to find and access. There is a need to provide metadata that describe cadastral documents to improve the usability of cadastral data for different user groups. The increasing interest in the use of such archival documents has stimulated their digitalization [20,21], and archival cadastral documents are accessed through a catalog, archive, or other means [22]. Furthermore, users can discover, view, and download cadastral documents through the catalogs of metadata [23]. Metadata records grouped in catalogs give users the possibility of identifying a source of interest [23]. Many authors research archival materials and develop an ontology for accessing archival content [24,25,26,27,28,29].

It is necessary to use well-defined content and adapt it to the metadata standard to expand the use and understanding of metadata among different user communities. The description of different types of data sources requires various types of metadata and different standards that they must meet [30]. The need for the development of metadata standards emerged with the advent of the electronic era to enable easier searching, organizing, and managing of data. Metadata standards are being developed in different areas, and the standards applicable to cadasters and cadastral documents include geoinformation metadata standards and standards for archival documentation. Many geoinformation metadata standards [23,31,32,33] have been developed at global, regional, and national levels, each with different scopes: Content Standard for Digital Geospatial Metadata (CSDGM), the ANZLIC Metadata Guidelines, the Dublin Core Metadata Initiative (DCMI), and ISO 19115 Geographic Information—Metadata [31,34,35,36,37]. Pivac et al. [38] explored catalogs containing archival cadastral documents and analyzed the metadata standards used to describe the documents. Most catalogs use ISAD(G) [39], the international standard for describing archival documentation [40], to describe cadastral documents, with a lack of application of geoinformation metadata standards that represent fundamental spatial datasets. Analog cadastral documents are scanned and described by metadata in accordance with archival metadata standards which do not provide enough information about the origin and quality of cadastral data. ISO 19115 was selected as the most suitable among all geoinformation metadata standards, and its applicability for describing analog cadastral documents of systematic cadaster establishment was examined.

Metadata of analog cadastral documents of a specific area of Croatia, including cadastral maps, cadastral municipality boundary demarcation records, a list of cadastral (land) parcels, a list of building parcels, and a list of possessors and their properties, were analyzed. The possibility of semantically mapping properties and metadata elements of the international standard ISO 19115-1 was examined to provide recommendations for extending the standard to make it applicable to describing cadastral documents. The first systematic cadaster was established in Croatia in the 19th century, resulting in the following documents: cadastral map sheets, cadastral municipality boundary demarcation records, a list of land parcels, a list of building parcels, and a list of possessors [38]. All analyzed data are identical or similar for other countries of the former Austrian-Hungarian Monarchy, as well as for the other countries with an established systematic cadaster.

The methodology and the materials used are presented in Section 2. The materials include metadata of analog cadastral documents which were stored in separate locations. Section 3 presents the four types of documents classified and their properties. The semantic mapping results of document properties with metadata elements of the international metadata standard are presented in Section 4. Extensions of some metadata elements are proposed to describe the cadastral documents. Section 5 discusses the developed methodology and semantic mapping results, and Section 6 summarizes the study and provides directions for future work.

2. Materials and Methods

The research workflow that resulted in the writing of this paper is presented in Figure 1. The methods used for the research are the inductive method, the method of analysis, and the method of classification. The inductive approach or method is a research approach involving the development of a theory based on the observation of empirical data [41]. There is not enough previous research about the standardization of metadata of archival cadastral documents, so it is necessary to explore documents stored in different locations and develop theories from them. This research began by collecting and analyzing the properties of analog cadastral documents from different periods of cadaster establishment stored in various locations, namely archives.

The materials for this research were cadastral documents developed between 1818 and 2000 for the territory of the Republic of Croatia. The cadastral documents were developed in different periods and stored in three locations: the State Archives in Zagreb, the State Archives in Split, and Januševec Castle. The properties or metadata of the cadastral documents are recorded in archive inventories, with a separate sheet of properties for each cadastral municipality. An example of a sheet for the cadastral municipality of Poljana stored in the State Archives in Zagreb is shown in Figure 2.

The properties highlighted in blue are: 1—the cadastral municipality identification number, 2—the name of the cadastral municipality, 3—the name of the stored document, 4—the year of creation of the document, and 5—the quantity of the document. All these properties are also available in the sheets of the State Archives in Split and Januševec. The names of key cadastral documents, which are result of cadaster establishment, are highlighted in red. Documents that resulted from the maintenance of the cadaster, and were not a result of cadaster establishment, were also stored in the archives and they are not included in this research.

The next step was a comparison of the terminology of documents between three locations. Different terminology was identified for documents with the same content in different archives by comparing the sheets. A total of five key documents were identified and systematized by comparing the content between documents: a cadastral map, a boundary demarcation record, a list of cadastral (land) parcels, a list of building parcels, and a list of possessors (

Table 1. The terminology used in the sheets from each archive. Source: own compilation.

Document	The State Archives in Zagreb	Januševec	The State Archives in Split
Cadastral map	Archival originals	Cadastral map	Original plans
Boundary demarcation record	Demarcation record (previous, final)	Demarcation record	Temporary boundary description Definitive boundary description
List of cadastral (land) parcels	List of cadastral parcels	List of parcels	Record of land parcels
List of building parcels	List of house parcels	-	Record of building parcels
List of possessors	-	-	Alphabetical index of possessors

).

Each of the key documents has additional unique properties that are not found in the archive inventories. The next step included analyzing each of the key documents to identified other properties that are important for users of cadastral data.

A cadastral map is created for the entire jurisdiction area during systematic cadaster establishment, namely the cadastral municipality. It is systematically divided into sheets of suitable dimensions which have a unique identifier—a sheet nomenclature. Furthermore, each sheet is uniquely identified by a sheet number within the cadastral municipality and contains the following information: the name of the cadastral municipality, scale, date of creation, signature of the person who created the sheet, signature of the person who certified the sheet, method of survey, and boundary coordinates of the sheet. A cadastral map can be created directly in the field or through the processing of survey data in the office, depending on the survey method. Different scales are used for creating cadastral maps: 500, 720, 1000, 1440, 2000, 2500, 2880, 2904, 5000, and 5760. Moreover, cadastral map sheets can be divided according to purpose and method of creation into original sheets, copies, lithographed copies of maintained sheets, and reambulation sheets. Original sheets are the result of cadaster establishment and contain the initial state at the time of the cadastral survey. They are stored in archives and are also known as archival originals, as in the State Archives in Zagreb. In the State Archives in Split, the term ‘original plans’ is used.

Copies are created from the original sheets, and all changes that occurred on the land are recorded on them. Lithographed copies of maintained sheets are the result of the lithography process that was carried out at the turn of the 19th to the 20th century. This is also one of the systematic renewals of cadastral documentation in Croatia. Reambulation sheets are the result of reambulation projects carried out in Croatia after long periods of systematic non-maintenance of a cadaster. Reambulation is a partial renewal of cadastral data conducted in one part of a cadastral municipality. The data obtained from reambulation are most often drawn on the original sheets, or new reambulation sheets are produced through the lithography process [2,42].

The cadastral municipality boundary demarcation record consists of the draft and textual description of the survey area. The draft shows the cadastral municipality with boundaries, settlements, main roads, and hydrographic networks. The textual description of a boundary includes the exact position and description of the edge of the cadastral municipality and the boundary marks. After the survey of cadastral parcels, the record is changed or updated as necessary, thereby creating two documents: the temporary and the final boundary records [8,43]. The boundary demarcation record contains the name of the cadastral municipality, date of creation, date of certification (in cases of changing the record), signature of the person who created the record, and signature of the person who certified the record. The terms ‘temporary’ and ‘definitive boundary description’ are used for the demarcation record in the State Archives in Split.

The list of cadastral parcels is in tabular form and contains all cadastral parcels of a cadastral municipality numbered using a series of numbers from 1 onwards. During the initial cadaster establishment, the built and non-built parcels were separately numbered from 1 onwards; thus, there were two separate documents: a list of land parcels and a list of building parcels. After the regulations in 1865, the unified numbering of parcels was introduced, so only one document was compiled—the list of cadastral parcels. The list of house parcels and the record of building parcels are found in the State Archives in Zagreb and the State Archives in Split, and they are synonymous with the list of building parcels.

The list of possessors contains a list of all the possessors in the cadastral municipality in alphabetical order and is only found in the State Archives in Split.

The list of cadastral (land) parcels, the list of building parcels, and the list of possessors contain the same properties: the name of the cadastral municipality, date of creation, signature of the person who created the list, and signature of the person who certified the list.

The key cadastral documents and their properties from the archive inventories were stored in the database for research purposes, with a total of 10,092 records collected for 2503 cadastral municipalities. For each record, the following attributes were identified: the cadastral municipalities’ identification number, names of the cadastral municipalities, document type, document quantity, year of creation, and storage location.

Cadastral documents are from different periods of systematic cadaster establishment. In the past, some areas of Croatia were parts of different countries, so cadastral development took place under various sociopolitical conditions and legislative frameworks [44]. Cadaster establishment is defined by regulations within the legislative framework of a country, so the adopted regulations are the reference basis for the distinction of different periods of cadaster establishment for one country. According to the regulations, the study periods were 1818–1883, 1884–1928, 1929–1952, 1953–1973, and 1974–2000 [42]. The number of each type of document by period is shown in Figure 3. Most documents were from 1818 to 1883 when the first systematic cadaster was established, with resurveys resulting in new cadastral documents for each cadastral municipality in other periods.

The number of each document by storage location in Figure 4 shows that most documents were stored in the State Archives in Zagreb, with the State Archives in Split containing the least documents. The documents of some cadastral municipalities were stored at multiple locations, limiting their accessibility. There was also a difference in the quantity of documents within each archive; for instance, the State Archives in Zagreb contained mainly documents pertaining to the list of cadastral parcels, cadastral maps in Januševec, and boundary demarcation records in the State Archives in Split. The list of possessors was found only in the State Archives in Split and was not compiled in areas whose documentation was stored in other locations.

An analysis of the key documents and their content enabled further classification of cadastral documents, which is presented in Section 3. For each classified document, unique properties were identified as a prerequisite for mapping with the ISO 19115-1 standard. The next step was mapping the document properties to the metadata elements of ISO 19115-1. Mapping included the selection of the appropriate type of resource for each classified document. The standard defines a total of 26 values for types of resources that can described by packages, classes, and metadata elements. Then, the document properties were associated with the relevant metadata element of the ISO 19115-1 standard. The obligation and domain for each associated metadata element were analyzed. The obligation is a descriptor indicating whether the metadata element is always or sometimes documented in the metadata: M (mandatory), C (conditional), or O (optional). Finally, extensions to the standard were proposed, ranging from mapping properties to metadata elements. Annex C in the standard guides extending metadata to better serve special user needs, allowing the following seven types of extension: a new metadata package, a new metadata class, a new metadata element, expanding a code list, a new metadata code list to replace the domain of an existing metadata element that has “free text” listed as its domain value, imposing a more stringent obligation on an existing metadata element, and imposing a more restrictive domain on an existing metadata element [37].

3. Classified Cadastral Documents with Identified Properties

Based on the analyzed key documents and their content, four types of documents were classified: cadastral documentation, a cadastral map sheet, a boundary demarcation record, and a list.

3.1. Cadastral Documentation

Cadastral documentation is the basic classified document representing the common name for all individual documents resulting from the process of cadaster establishment for a cadastral municipality. Cadastral documentation is classified at the highest level and, as such, it has common properties which apply to all individual documents.

Multiple cadaster establishments for a cadastral municipality result in more cadastral documentation, the number of which can be determined by using the cadastral map, the list of cadastral parcels, and the list of possessors [42]. The recognized properties for the cadastral documentation are presented in

Table 2. Properties of the cadastral documentation. Source: own compilation.

Properties	Description	Example
Name	The name of the cadastral documentation	Cadastral documentation of cadastral municipality Poljana
Purpose	The purpose of creating the cadastral documentation can be fiscal, legal, or multipurpose	Fiscal
Beginning of application	The beginning of the application of the cadastral documentation	1883-01-01
End of application	The end of the application of the cadastral documentation	-
Regulation	The name of the regulation that defines the creation of the cadastral documentation	Land Tax Act (Grundsteuerpatent) [8]
Date of publication	The date of publication of the regulation	1817-12-23 [8]
Cadastral municipality identification number	Unique cadastral municipality registration number	334855
Name of cadastral municipality	The name of the cadastral municipality for which the cadastral documentation was created	Poljana
Origin	The survey method used to produce the cadastral documentation	Graphical
Language	The language of cadastral documentation	Italian
Coordinate system	The coordinate system in which the parcels are determined	Viennese
Type of coordinate system	The type of coordinate system can be rectangular without using projection or projected	Rectangular without using projection
Storage	The organization responsible for storing, maintaining, and issuing documentation; this can be accompanied by the address and contact information	The State Archives in Zagreb Opatička 29 10000 Zagreb Croatia email: [email protected] Tel.: +38514807150

.

A total of 13 properties describing the cadastral documentation were identified. The beginning of application of the cadastral documentation depends on the period of cadaster establishment. In the first period from 1818 to 1883, all cadastral documentation was officially implemented in 1883 [8]. In other periods, the year of cadastral map creation can be used as the beginning of the application, with the year of the cadastral map creation in the subsequent period used as the end of the application. There was no end of application for the cadastral municipality Poljana because the cadastral documentation from 1883 is still in official use.

The quality of cadastral data depends on the survey method used for the cadastral establishment. Information about the survey method is of exceptional importance and applies to the entire cadastral documentation. Survey methods have changed throughout history, and the methods used in this research area are graphical, orthogonal, polar, land consolidation, photogrammetric, and satellite. All cadastral documentation from 1818 to 1883 was created using the graphical method [8]. The orthogonal and polar methods began to be applied at the beginning of the 20th century, while photogrammetric and land consolidation methods were used in the second half of the 20th century. Furthermore, satellite methods for cadastral establishment began to be intensively applied with the development of global satellite systems at the beginning of the 21st century. For some cadastral documentation, a combination of two survey methods was used, e.g., orthogonal and polar [2].

The languages used for cadastral documentation included German, Italian, Croatian, Hungarian, and Serbian.

The coordinate reference systems varied depending on the cadaster establishment period, with cadastral documentation created in one coordinate system. Four rectangular coordinate systems were used in periods 1818–1883 and 1884–1928 with origins in St. Stephan (Viennese), Krimberg (Crimean), Gellérthegy (Budapest), and Kloštar Ivanić. The systems are rectangular coordinate systems without using cartographic projection [8]. In the other periods, Gauss–Krüger projection coordinate systems were used, namely the fifth and sixth systems.

It is important to provide the user with information about the storage of cadastral documentation. The organization responsible for storage is also responsible for maintaining and issuing documentation.

All identified properties at the level of cadastral documentation apply to the other three classified cadastral documents. However, each classified document has its unique properties. The individual documents analyzed along with their properties are listed below.

3.2. Cadastral Map Sheet

The most important part of the cadastral documentation is the spatial representation of cadastral parcels, i.e., the cadastral map, which consists of individual sheets. The cadastral map sheet is divided into useful areas and sheet frames. The useful space contains data about land features, while the sheet frame contains metadata such as the name of the cadastral municipality, responsible person, authorized person, scale, boundary coordinates, survey method, etc. An example of a cadastral map sheet with metadata is shown in Figure 5.

The cadastral maps have unique properties or metadata, as shown in

Table 3. Properties of cadastral map sheet. Source: own compilation.

Properties	Description	Example
Name	The name of the cadastral map sheet	The cadastral map sheet of cadastral municipality of Šuma Striborova
The creation process	Cadastral map sheets can be divided according to the purpose and method of creation into original sheets, copies, lithographed copies of maintained sheets, and reambulation sheets	Original
Date of creation	Date of creation of the sheet	1981-01-01
Responsible person	The name of the physical/legal person who created the sheet	Authorized geodetic company
Authorized person	The name of the physical/legal person who certified the sheet	Regional Cadastral Office
Scale	The scale at which the sheet is made	1:1000
Identifier	Nomenclature and sheet number	5B10-2-1
Format	The sheet can be produced in analog or electronic format	Analog
Spatial extent	The spatial extent of the sheet is defined by its boundary coordinates	Y1, X1, Y2, X2, Y3, X3, Y4, X4.

.

A total of nine properties describing a cadastral map sheet were identified, and the total number of sheets is available in the list of documents for the cadastral municipalities (Figure 2, label 5). This format distinguishes between analog and electronic cadastral map sheets. All sheets of the research data are in analog format. Other properties, such as the date of creation, responsible person, authorized person, scale, identifier, and spatial extent, are in the useful space, with the survey method being a property of cadastral documentation.

3.3. Boundary Demarcation Record

In addition, another document containing a spatial representation is the draft, which, together with the textual description, forms the boundary demarcation record (it. Protocollo). An example of the textual description of the cadastral municipality of Dol stored in the State Archives in Split is shown in Figure 6. The textual description of the boundary (it. Descrizione confini) contains metadata such as the name of the cadastral municipality (it. Comune), date of creation, responsible person, and authorized person. The draft also contains all the above metadata.

The draft and textual description were created in the same year by the same responsible person and certified by the same authorized person. They are classified as one document, the boundary demarcation record. Each boundary demarcation record can be described by a total of six properties in

Table 4. Properties of the boundary demarcation record. Source: own compilation.

Properties	Description	Example
Name	The name of the record	Demarcation record of the cadastral municipality of Dol
Abstract	Abstract of the record	Draft, textual description
Date of creation	Date of creation of the record	1833-09-12
Date of certification	Date of certification of the record (in the case of changing and updating the record)	1835-11-02
Responsible person	The name of the physical/legal person who created the record	Illegible
Authorized person	The name of the physical/legal person who certified the record	Illegible

.

In the case of the two boundary demarcation records, previous and final, two properties were identified: the date of creation and date of certification. When the record has not been changed or updated, the date of creation and the date of confirmation will be the same. The boundary demarcation record changed after two years for the cadastral municipality of Dol, so there is a difference between the dates of creation and certification.

3.4. List

The list refers to all lists that arise from the cadaster’s establishment: cadastral parcels, land parcels, building parcels, and possessors. An example of the list of possessors for the cadastral municipality of Dol is shown in Figure 7 and contains metadata such as the name of the cadastral municipality, date of creation, responsible person, and authorized person.

Each list can be described by a total of five properties in

Table 5. Properties of the list. Source: own compilation.

Properties	Description	Example
Name	The name of the list	The list of possessors of the cadastral municipality of Dol
Abstract	Abstract of the list. The list can contain cadastral parcels, land parcels, building parcels, and possessors.	Possessors
Date of creation	Date of creation of the list	1877-02-25
Responsible person	The name of the physical/legal person who created the list	Illegible
Authorized person	The name of the physical/legal person who certified the list	Illegible

.

All lists are described by common properties: the date of creation, responsible and authorized person, and abstract vary depending on what the lists contain.

A prerequisite was created by classifying documents with their key properties for further mapping with the metadata elements of the international standard ISO 19115-1.

4. Semantic Mapping of Classified Cadastral Document Properties with Metadata Elements of ISO 19115-1

The next step was the semantic mapping of the properties of the classified cadastral documents with the appropriate metadata elements of the ISO 19115-1 standard, including the packages, classes, and metadata elements used to describe a resource. Thirteen packages were used to define and describe the metadata, with an additional four packages used by other packages. Each package consisted of one or more metadata classes containing elements that identify discrete units of metadata.

The first step was the selection of the appropriate type of resource that corresponded to the classified documents: cadastral documentation, a cadastral map sheet, a boundary demarcation record, or a list. The standard defines a code list (MD_ScopeCode) with a total of 26 values for each resource. For classified documents, two values were selected and identified: series and dataset. The cadastral documentation consisted of a set of various documents with common properties. The type of resource selected for the cadastral documentation was series, which represents a series of datasets with common properties. For other individual classified documents, the type of selected resource was dataset, which represents the identified set of data.

Next, the document properties were semantically mapped to the corresponding metadata element of the standard. The obligation and the domain were analyzed for each element: the obligation values were M (mandatory), C (conditional), or O (optional), and the domain values were another class (code list), an unrestricted text value (free text), or an alphanumeric set of characters (unspecified domain).

Extensions to the standard were also proposed to describe the documents of systematic cadaster establishment. The definitions and domain values are intended to be sufficiently generic to satisfy the metadata needs of various disciplines.

4.1. Cadastral Documentation—Series

The cadastral documentation is the first resource for which the associated metadata elements are mapped (

Table 6. Mapping data of cadastral documentation to ISO 19115-1. Source: own compilation.

Property	Metadata Element (ISO 19115-1)	Obligation	Domain
Name	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.title	M	Free text
Purpose	MD_Metadata.identificationInfo > MD_DataIdentification.purpose	M *	CodeList *
Beginning of application	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation > CI_Date.date [dateType = ‘validityBegins’]	M *	DateTime (ISO 8601)
End of application	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation > CI_Date.date [dateType = ‘validityExpires’]	C *	DateTime (ISO 8601)
Storage	MD_Metadata.identificationInfo > MD_DataIdentification.pointOfContact > CI_Responsibility > CI_Organisation.name [role = ‘custodian’] Optional: contactInfo > CI_Contact.address > CI_Address.deliveryPoint/postalCode/city/country/electronicMailAddress contactInfo > CI_Contact.phone > CI_Telephone.number [numberType = ‘voice’]	M *	Free text
Cadastral municipality identification number	MD_Metadata.identificationInfo > MD_DataIdentification.extent > EX_Extent.geographicElement > EX_GeographicDescription.geographicIdentifier > MD_Identifier.code	M	Free text
Name of the cadastral municipality	MD_Metadata.identificationInfo > MD_DataIdentification.extent > EX_Extent.geographicElement > EX_GeographicDescription.geographicIdentifier > MD_Identifier.description	M *	Free text
Language	MD_Metadata.identificationInfo > MD_DataIdentification.defaultLocale > PT_Locale.language	M	LanguageCode * (ISO 639-3)
Coordinate system	MD_Metadata.referenceSystemInfo > MD_ReferenceSystem.referenceIdentifier > MD_Identifier.description	M *	CodeList *
Type of coordinate system	MD_Metadata.referenceSystemInfo > MD_ReferenceSystem.referenceSystemType	M *	MD_ReferenceSystemTypeCode *
Origin	MD_Metadata.resourceLineage > LI_Lineage.statement	M *	CodeList *
Regulation	MD_Metadata.resourceLineage > LI_Lineage.additionalDocumentation > CI_Citation.title	M	Free text
Date of publication	MD_Metadata.resourceLineage > LI_Lineage.additionalDocumentation > CI_Citation.date > CI_Date.date [dataType = ‘publication’]	M *	DateTime (ISO 8601)

* Different obligation/domain compared to the standard.

). Most properties are mapped with the class MD_DataIdentification, which is part of the Identification information package. Other identified classes are MD_ReferenceSystem, belonging to the Reference system information package, and LI_Lineage, which is part of the Lineage information package. In addition to the basic packages, properties are mapped with elements of classes belonging to additional packages: Citation information, Responsible party information, Language-characterset localisation information, and Extent information.

Each property is associated with a metadata element, an obligation, and a value domain. For certain elements, a more stringent obligation is imposed compared to the standard to provide a more detailed description of the resource. Most elements that are optional in the standard are proposed here as mandatory. The end of the application is defined as conditional because there are cases where the cadastral documentation is still in use. The domain of allowed values is free text for most elements in the standard. For elements whose domain is marked with *, a change in the value domain compared to the standard is proposed. For language, the value LanguageCode is selected from the ISO 639-3 code list [45], which consists of three letters. For the description of cadastral documentation, the code list is limited to a total of five languages used in the research area: ger, ita, hrv, hun, and srp. For this purpose, instead of free text, a code list with three values is proposed—fiscal, legal, and multipurpose. For origin, the free text is replaced with a code list of seven values: graphical, orthogonal, polar, land consolidation, photogrammetric, satellite, and combined.

A coordinate system is described by two elements, description and referenceSystemType, and six coordinate systems were used in this study. A code list of six values was proposed for description: Viennese, Budapest, Crimean, Kloštar Ivanić, Gauss–Krüger fifth system, and Gauss–Krüger sixth system. MD_ReferenceSystemTypeCode was selected for referenceSystemType. Out of a total of 28 values, two values were selected for this study: projected and engineering. The value projected is associated with the Gauss–Krüger system, while other rectangular systems were associated with engineering. The domain is the DateTime class defined by ISO 8601 [46]. Three values were selected from the CI_DataTypeCode code list for the data type: validityBegins, validityExpires, and publication. The proposed format for all dates was YYYY-MM-DD (year, month, and day).

4.2. Cadastral Map Sheet—Dataset

The cadastral map sheet is defined as the dataset for which the associated metadata elements are mapped (

Table 7. Mapping data of cadastral map sheet to ISO 19115-1. Source: own compilation.

Property	Metadata Element (ISO 19115-1)	Obligation	Domain
Name	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.title	M	Free text
Date of creation	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation > CI_Date.date[dateType = ‘creation’]	M *	DateTime (ISO 8601)
Responsible person	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.citedResponsibleParty > CI_Responsibility > CI_Organisation.name or CI_Individual.name [role = ‘author’]	M *	Free text
Authorized person	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.citedResponsibleParty > CI_Responsibility > CI_Organisation.name or CI_Individual.name [role = ‘rightsHolder’]	M *	Free text
Scale	MD_Metadata.identificationInfo > MD_DataIdentification.spatialResolution > MD_Resolution.equivalentScale > MD_RepresentativeFraction.denominator	M	CodeList *
Identifier	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.identifier > MD_Identifier.code	M	Free text
Format	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.presentationForm	M *	CI_PresentationFormCode *
Spatial extent	MD_Metadata.identificationInfo > MD_DataIdentification.extent > EX_Extent.geographicElement > EX_BoundingPolygon.polygon > GM_Object	M	Class (ISO 19107 [47])
The creation process	MD_Metadata.resourceLineage > LI_Lineage.statement	M *	CodeList *

* Different obligation/domain compared to the standard.

). The metadata elements of the cadastral map sheet belonged to packages Identification information and Lineage information, and the properties were also mapped with elements of classes belonging to the additional packages Citation information, Responsible party information, and Extent information.

Each property describing the cadastral map sheet is associated with a metadata element, an obligation, and a value domain. For certain elements, a more stringent obligation is imposed compared to the standard. Most elements that are optional in the standard are proposed here as mandatory (M*). A change in the value domain compared to the standard was proposed for elements whose domain is marked with *. For the domain of scale (denominator), a code list of ten values was proposed (500, 720, 1000, 1440, 2000, 2500, 2880, 2904, 5000, and 5760) instead of Integer > 0. These values are denominators of the scales used to produce the cadastral map sheets. CI_PresentationFormCode was selected for format (presentationForm), and mapDigital and mapHardcopy were selected for the research area. The free text was replaced with a code list of two values for the domain of statement: field and office. For dataType, the value creation was selected from the CI_DataTypeCode code list. The proposed format for all dates was YYYY-MM-DD (year, month, and day).

4.3. Boundary Demarcation Record—Dataset

The boundary demarcation record is defined as the dataset resource type. The results of semantic mapping between the properties of the record and metadata elements are shown in

Table 8. Mapping data of boundary demarcation records to ISO 19115-1. Source: own compilation.

Property	Metadata Element (ISO 19115-1)	Obligation	Domain
Name	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.title	M	Free text
Abstract	MD_Metadata.identificationInfo > MD_DataIdentification.abstract	M	CodeList *
Date of creation	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation > CI_Date.date[dateType = ‘creation’]	M *	DateTime (ISO 8601)
Date of certification	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation > CI_Date.date[dateType = ‘adopted’]	M *	DateTime (ISO 8601)
Responsible person	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.citedResponsibleParty > CI_Responsibility > CI_Organisation.name or CI_Individual.name [role = ‘author’]	M *	Free text
Authorized person	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.citedResponsibleParty > CI_Responsibility > CI_Organisation.name or CI_Individual.name [role = ‘rightsHolder’]	M *	Free text

* Different obligation/domain compared to the standard.

. The metadata elements of the boundary demarcation records belong to the Identification information package. In addition to the basic packages, the properties are mapped with elements of classes belonging to the additional Citation information and Responsible party information packages.

Each property describing the record is associated with a metadata element, an obligation, and a value domain. For certain elements, a more stringent obligation is imposed compared to the standard, with most optional elements in the standard proposed here as mandatory (M*). The free text in abstract was replaced with a code list of two values: the draft and textual description. For dataType, two values were selected from the CI_DataTypeCode code list: creation and adopted. The proposed format for all dates was YYYY-MM-DD (year, month, and day).

4.4. List—Dataset

The list is defined as a dataset resource type. The results of the semantic mapping between the properties of the list and the metadata elements are shown in

Table 9. Mapping data of list to ISO 19115-1. Source: own compilation.

Property	Metadata Element (ISO 19115-1)	Obligation	Domain
Name	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.title	M	Free text
Abstract	MD_Metadata.identificationInfo > MD_DataIdentification.abstract	M	CodeList *
Date of creation	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation > CI_Date.date[dateType = ‘creation’]	M *	DateTime (ISO 8601)
Responsible person	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.citedResponsibleParty > CI_Responsibility > CI_Organisation.name or CI_Individual.name [role = ‘author’]	M *	Free text
Authorized person	MD_Metadata.identificationInfo > MD_DataIdentification.citation > CI_Citation.citedResponsibleParty > CI_Responsibility > CI_Organisation.name or CI_Individual.name [role = ‘rightsHolder’]	M *	Free text

* Different obligation/domain compared to the standard.

. The metadata elements belong to the Identification information package. In addition to the basic packages, the properties were mapped with the elements of the classes belonging to the Citation information and Responsible party information packages.

Each property describing the list is associated with a metadata element, an obligation, and a value domain, with most optional elements in the standard being proposed as mandatory (M*). The free text in the abstract was replaced with a code list of three values: cadastral parcels, building parcels, and possessors. For dataType, the value creation was selected from the CI_DataTypeCode code list, and the proposed format for all dates was YYYY-MM-DD (year, month, and day).

5. Discussion

This study focused on the standardization of analog cadastral document metadata resulting from the systematic cadaster establishment in Croatia. All analyzed data are identical or similar to those of other countries in Central Europe with systematic cadaster establishment [38]. Pivac et al. [38] examined the availability of cadastral documents from the Franciscan cadaster in catalogs and the applicability of geographic information metadata standards and archival metadata standards for describing documents. The establishment of the Franciscan cadaster occurred in most Central European countries in the 19th century. Most of documents in catalogs are described by the ISAD(G) standard. The semantic mapping of the elements of the applied standards in the catalogs and the elements of ISO 19115-1 showed a considerable congruence of elements. This research only included analog cadastral documents from one period of cadaster establishment, so it is ecessary to include documents from different periods.

The adopted regulations are the basis for the distinction of different periods of cadastral establishment for one country. There were five periods in the study area, with most documents from the first period of 1818 to 1883, when the first systematic cadaster establishment was conducted. In addition, documents were stored in three separate locations, the State Archives in Zagreb, the State Archives in Split, and Januševec Castle, making the cadastral data difficult to access. The documents of some cadastral municipalities were stored at multiple locations, limiting their accessibility.

The metadata of archived cadastral documents are recorded in inventories compiled by cadastral municipalities, with different terminology used for documents with the same content in the inventories in each archive. Our comparison and analysis of the content of documents between archives identified four different types of documents: cadastral documentation, a cadastral map sheet, a boundary demarcation record, and a list. Each classified document was associated with properties or metadata that uniquely describe it. Cadastral documentation was classified at the highest level and, as such, has common properties that can be applied to other classified documents. Most properties were identified for cadastral documentation, a total of 13. The cadastral map consists of individual sheets that differ from each other based on nine unique properties. The list is the common name for all lists from the cadaster establishment. All can be grouped into one document, which can be described by five properties. The boundary demarcation record consists of a draft and a textual description and can be described by six properties.

Property identification for classified documents enabled further semantic mapping to metadata elements of the international standard of ISO 19115-1. First, the resource type was selected for the classified documents, series for cadastral documentation, and dataset for the other documents. All properties of the classified cadastral documents were mapped to three basic and four additional packages. The Identification information package is the only mandatory element in the standard and was used to describe each classified document. Other basic packages applied included Reference system information and Lineage information.

Although the semantic mapping to the metadata elements of the standard was successful, it was necessary to extend the standard to describe the cadastral documents by replacing the free text with domains of appropriate values, adding stricter obligations, and restricting the use of domain values (

Table 10. Percentage of cadastral document elements with a different obligation and domain according to ISO 19115-1:2014.

Document/Resource	Number of Properties (Elements)	Elements with a Different Obligation		Elements with a Different Domain
		Number	Percentage	Number	Percentage
Cadastral documentation	13	9	69%	5	38%
Cadastral map sheet	9	5	56%	3	33%
Boundary demarcation record	6	4	67%	1	17%
List	5	3	60%	1	20%

).

Most metadata elements, defined as optional in the standard, were mandatory for classified cadastral documents. A mandatory obligation was proposed for more than 50% of the elements defined as optional in the standard, with a different domain proposed for less than 50% of the elements. The different domains included replacing the free text with appropriate values (code list) and restricting the use of domain values allowed by the standard.

There is a need to create an appropriate catalog of metadata that will contain scanned classified documents from systematic cadaster establishment to improve the usability of cadastral data for different user groups. Each document would be described by metadata elements according to the standard ISO 19115-1, along with the additional extensions proposed in this research. It is possible to add new values for metadata elements that have code lists for their values. Creating a metadata catalog requires collaboration between the relevant cadastral data institutions and the archives where the analog cadastral documents are stored.

6. Conclusions

A systematic approach to the establishment of the cadaster resulted in a variety of cadastral documents from different periods which were stored in analog format in separate locations, making the cadastral data difficult to access. Metadata that describe analog cadastral documents were recorded in inventories compiled by cadastral municipalities. Our analysis and comparison of the properties and content of documents between archives identified four different document types: cadastral documentation, a cadastral map sheet, a boundary demarcation record, and a list.

The properties that uniquely described each document were identified, with the high-level cadastral documentation having the largest number of properties. The semantic mapping of the properties and metadata elements of the international standard of ISO 19115-1 showed a considerable congruence of elements, so it was possible to apply ISO 19115-1 for describing documents of systematic cadaster establishment with additional extensions for some elements. The most applied extension was stricter obligations, making optional elements mandatory.

The standardization of metadata for analog cadastral documents in archives has created a prerequisite for the development of a metadata catalog, which would increase the availability and accessibility of cadastral data for different user groups. The scientific contribution of this study lies in the classification of key documents and their associated properties, which uniquely describe the documents. The proposed structured and standardized metadata elements provide a scientific contribution to improving the accessibility of cadastral data via web services. This study focused on analog documents of systematic cadaster establishment, so future research could include documents that are currently archived in electronic format.