by Dr. Ing. Winfried Hawerk
The objective of the symposium is to elaborate on the cadastral options, namely the legal, institutional, land policy and technical options. This paper tries to give an overview about technical options to establish and to maintain cadastral systems.
It will not be possible to design a cadastral system suitable for any case and any circumstances. Specially the socio-economic basic conditions are different from country to country. The different forms of land tenure and the legal situation in this field will give the framework for a cadastral systems and how to carry out its technical features. On the other hand the political circumstances are dictating the financial and personnel investment in the cadastral system. Third but last the countrys infrastructure (nature, traffic, technical infrastructure, education etc.) will influence technical options in establishing a cadastral system too.
Which are the objectives for establishing and maintaining a cadastral system in a developing country? There will be different technical standards to design a cadastral system depending on the definition what to do with such a tool, i.e.
The technical design of a cadastral system in a developing country needs a precise definition of the requirements and aims at such a system. A cadastral system is not a monolithic block. It should be designed to fulfil the changing legal demands and demands of administration and the private sector. It should be able to develop it into a basic Land Information System (LIS) of great variety and flexibility for planning, environmental protection etc.
2. Cadastral systems to secure land tenure
2.1 Development of cadastral systems
Specially in densely populated areas on earth land is the most important asset and the most important means of production of the people. Therefore in most developed countries land ownership is especially secured and guaranteed by governmental organisations.
To secure land tenure it is necessary to define three different legal positions: how to own land, how to get land and how to save the ownership. Different forms of societies have different point of views of secure land tenure and the points of view are developing so the cadastral systems may change by social, economic and political demands like shown as follows with the example of Germany.
Security of land tenure in Germany has a tradition of some centuries. The forms of land registration in former centuries had great variety because of the great number of independent states on the territory of the present Federal Republic of Germany. The basic laws have been quite different as well, because since the end of the 30 years war in 1648 states as Prussia or Saxonia have been completely independent.
At the beginning of the 19th century in some of the kingdoms cadastral systems have been established for taxation purposes. Until 1876 the cadastre in Prussia was completed. Although the main purpose for establishing a cadastre was taxation of land, but the idea of using maps and records for further purposes of governmental activities was implemented in the cadastral systems from the beginning.
After Germany was founded in 1871, the need of standardisation of the private law was evident. Since January, 1, 1900 the common private law exists for the whole country. In connection with this law the land registration system for the whole country has been established. This land registration system (in German terms called Grundbuch") contents all rights of ownership and other rights on land and buildings. By establishing this Grundbuch system the importance of good working cadastral system grew very fast. The description of the land parcels (parcel identifier and cadastral maps) became the official and legal register of parcels as a part of the land register. Cadastre developed from a system for taxation of land to a register that gives guarantee to the right of land tenure.
After 1934 the results of the official soil assessment have been recorded in the cadastre. This was the first step into the direction of a multi-purposed cadastre.
The constitution of the Federal Republic of Germany accords responsibility for legislation around the land register to the Federal Republic whereas the states make the laws concerning the property cadastre. Interstate bodies (working groups of state survey agencies) ensure uniformity of the property cadastre.
In these days the cadastre fulfils all legal demands and demands of administration and the private sector. It is a basic Land Information System (LIS) of great variety and flexibility in planning, environmental protection etc. Maps and cadastral records in most parts of Germany are stored in computer systems. Although cadastre in Germany is in the responsibility of the 16 states the computerised systems are unique with some small exceptions. These systems are the automated cadastral map (ALK) and the automated property register (ALB).
This historical review of the development of the cadastre in Germany shows that this system is not a static one. The modern form of cadastre is a multi-purposed cadastre as it is described as well in the FIG Statement on the cadastre.
Even in developing countries cadastral systems should be designed to give options for using it as a basic Land Information System.
2.2 The important role of the cadastre in the society
Most jurisdictions have some form of registration of legal documents, ownership, or use rights. In some cases a new system may be introduced to replace existing systems or informal arrangements.
In the Federal Republic of Germany a good working system to guarantee the security of land tenure has been established. With a long history of land registration in this country it is a proven fact that a good working system of security of land tenure is very important for a developed society and as well for a developing country. The consequences of a land registration system badly maintained or even not existing can be demonstrated with the experiences in the new states of Germany after the unification. Investments in land and buildings have been very difficult or even not been possible before re-establishing a land registration system like in the rest of the country. The German system of land registration is a dual one, land registration and cadastre are established in different organisations. The cadastral system in this country with its additional contents in maps and records now has the function of a basic Land Information System.
2.3 Legal demands for a working cadastral system
The role of a land registration system like the cadastre should be regulated by laws and other administrative rules and guidelines for a uniform implementation of the system. These regulations should content as well some technical demands and rules for using the system and for maintaining it.
3. Cadastre as a basic Land Information System
The cadastre forms part of the base data required in any public land information system (LIS) normally in digital form. Therefor technical standards have to be defined and accepted by all users of these data. In Hamburg, a city of approximately 1.7 million people this digital LIS is completed 100 % and in practice since some years.
To make sure that there is no double-work on digitising maps and describing data some regulations have been established by the authorities:
To be effective the system should be clear and simple to use. Complex forms, procedures and regulations slow the system down and discourage the use of the system.
In Hamburg digital maps in different scale-levels with easy access (vector data or raster data are available) and acceptable costs guarantee a great number of users and good economical success.
4. Contents of a parcel-based real property-cadastre
The cadastre in Germany is defined as the official register of all parcels and buildings. The real property cadastre is designed to show the de facto status of property. The cadastre therefor is the only register in which all parcels and buildings in a state are described.
Normally the cadastre is a system of different forms of official documents mainly
All these information are linked to each other by the unique parcel-identifier.
4.1 Cadastral records
The cadastral records content all describing data to the parcels. These records can be kept in books, record cards or in a data-base on a computer. The form of the data-base may be held on a local PC-system like MS Access in a very simple manner or in a nation-wide operating computer-system. This is just a question of money and know-how and not of the cadastral system. The use of PC based software should be the state of the art for a developing country because the equipment is not very expensive. The analogue way is not very useful for statistics and other data processing but if the technical infrastructure (electricity supply etc.) doesnt allow any other solution then analogue data processing is a good way in the beginning. Normally analogue processes can be formed in a computer data base.
Making the data base simple may be the right way to start a cadastral system in a developing country. So it will be maintained and accepted by a great number of users. In Germany a relational data base called ALB is used for storing the cadastral records. Additional contents allow links between data bases of other institutions so this data base is the basic part of a land information system. The data can be given away on paper as well as in form of normal ASCII-files so that customers can use these data as input in their special PC based data bases. Links to the graphical part of the cadastre via the parcel number are possible. Still the parcel and its identifier (parcel number) seems to be the easiest and best imaginable basic unit for most purposes. Development of more sophisticated data bases are object oriented. There all information are linked to points, polygons etc. Parcels are formed out of these objects. This kind of data base has a lot of benefits but the design is very complicated one so that developing countries should not start building up a cadastral system with such a data base design.
Minimal elements of the cadastral records should be the parcel number, the name of the land owner and the size of the parcel. Additional elements can be registered as well but this is always a balance between cost and benefit and should only be registered if the maintenance is organised. Stored details for each parcel in the cadastral records may be
4.2 Cadastral maps
The cadastral maps should be based on one nation-wide existing coordinate-system. In Germany this is the Gau¤-KrĘger-System that will be transformed into ERTS89 and UTM like in all European nations in the near future. In urban areas it is very useful to have grid-maps in just one scale. These maps can be used very easy for planning and other purposes.
In Hamburg the analogue cadastral maps exist generally in form of grid-maps scale 1:1000 based on Gau¤-KrĘger-coordinates. These analogue maps have been replaced by digital maps (ALK) via digitising. These maps contain geographical information about
The establishment of cadastral maps in digital form can be realised in a very simple way as a so called spaghetti map" by not creating so called graphic objects. This is the simple way getting digital maps but will not give the opportunity to add describing information and to use the map as a basic land information system. A great number of easy to handle and easy to learn software is available e.g. AutoCAD.
In Germany an object oriented digital cadastral map ALK is in use but only in some parts already completed. This very high sophisticated mapping system may not be the right solution for a developing country. It is more important to complete the data nation-wide in a short time so the benefits will be available earlier. It is better to start simple and to get ready in time than to start complicated and never be ready.
In Hamburg a system called DSGK (a light version of ALK) is in operation by the cadastral administration. This map was completed for the whole state in a time of four years (755 kmÖ urban area). The elements of this map can be linked to additional information of other data bases. Because of 100 % availability the DSGK is used by a wide range of different institutions of the public and private sector. The map is available as vector and as raster data.
Marketing these digital data indicated that a great number of users require an easy to handle low-cost PC software system to present the graphical maps. Together with the German company megatel the product DSGK/visor was created. Now software and data are distributed by the survey department of Hamburg (published in GIS Europe July 1996, page 40). So a wide range of more than 50 different users require DSGK and updates. The system runs cost-recovering.
As an example of an official extract of ALB and ALK see enclosure 1. Because ALB and ALK are held in digital form extracts can be put together individually following the requests of the user in analogue listings, micro-films, plots or digital in well defined formats (e.g. DXF, TIFF).
The cadastral maps should be suitable as a basis for development plans and for the revision of the official map series. According to the legal tasks of the cadastral maps the contents are based on terrestrial surveys (boundaries, houses and buildings). Topographical details sometimes may be put into the maps by photogrammetry.
5. Technical methods for cadastral surveying
Parcel boundaries usually are defined by stable marks on the ground. In urban areas the boundaries may be identified as well by buildings. Physical demarcation on the ground is important because it provides actual notice of the boundaries to the landowners. In some states in Germany the boundaries are defined by the surveyed and calculated coordinates. This way of defining boundaries is very useful in areas under construction because then very often the monuments are lost immediately after putting them into the ground.
The demarcation and delineation of the boundaries are part of a cadastral survey aimed at defining the parcels on the ground and securing evidence for the re-establishment of the boundary if the marks disappeared. The accuracy of these cadastral surveys should be related to the value of the land and being regulated by official instructions for the whole country. These accuracy instructions are indicating the necessary survey methods.
Even in developed countries like Germany more and more cadastral surveys are undertaken by using aerial photographies especially in the former socialist part of the country. The accuracy of the surveyed coordinates of parcel boundaries, buildings and other topography depends on the scale of the photographs. High accuracy and efficiency can be obtained using analytical or digital photogrammetric methods but even using analogue methods can be much more efficient than ground survey methods. Terrestrial works has to be done only by marking the boundaries and surveying the ground control points. Using the Global Positioning System (GPS) for navigation of the aeroplane can minimise the costs for ground surveys drastically.
In urban areas the scale of the aerial photographs should range between 1:3000 and 1:8000. So the accuracy for each stereoscopic measured point can be about some centimetres. In regions not very populated even satellite images can be used.
|cost-effective aerial photographs||expensive equipment|
|high content of information||education necessary|
|actuality||central perspective, restitution|
|very fast method||clouds, visibility|
5.2 Ground Survey
Ground survey methods for cadastral surveys need control points measured from trigonometric points of the national land survey authorities. The measurements to create and maintain this grid of control points are very cost-intensive. These costs can be minimised by using Differential GPS (DGPS).
Cadastral surveys can be undertaken using low-cost or high sophisticated equipment. The method chosen will be influenced by the accuracy demanded. In rural areas even the plane tables may be the right equipment. This is only dependent to the budget that will be available. The most cost-efficient method is the Total station that calculates already the coordinates and guarantees a good data flow from the survey to the digital map. The major principle of surveying boundaries and buildings is controlling the work by an independent second measurement.
In areas with a high accurate cadastre and where the coordinates represent the legal boundaries it is possible to create new legal boundaries from existing plans by calculating without surveying in the field.
Final result of this work will be coordinates for all surveyed boundaries respectively corner points of parcels and buildings and control points. These coordinates are stored in a point file indicating nature of point, status, accuracy and reliability.
Established boundaries should be marked. The same applies to newly constructed parcel boundaries or boundaries settled by arrangement or judgement. Establishing and marking of boundaries' proceedings involve the hearing of concerned land owners, who are to be notified in due course about date and location of the procedure. A record of the proceedings is to be taken (Demarcation Record) a copy of which may be forwarded to the owners involved.
Land owners and long-term leaseholders are obliged to inform the competent authorities about relevant changes pertaining their land; this applies especially to the construction of new buildings or changes to the exterior plan of existing buildings. Any necessary surveyings are at the expense of the owner.
Access to survey plans and point file should be allowed only to persons who guarantee a proper use of the data.
5.3 Global Positioning System (GPS)
GPS is a world-wide operating system of satellites for navigation. In the field of surveying with high accuracy (some centimetres) GPS can be used as DGPS with a reference station on a surveyed control point. GPS is used for cadastral surveys especially in rural areas. Mostly hybrid methods of using GPS where it is possible and using Total stations where GPS doesnt work (under trees or near buildings) are very cost-effective.
|high accuracy DGPS||not under trees or near buildings|
|no control points necessary||special software|
|data flow||equipment expensive|
Some technical options for establishing and maintaining a cadastral system have been described. There will be no perfect solution for all political and social systems. The investment in a cadastral system is only worth if the cadastre is part of system to secure land ownership and which is accepted by the society and maintained by governmental bodies. It should be able to operate as a basic land information system.
Land registration and cadastre are subject to the public sector. Therefor these systems should be financed through governmental funding. Part of the costs are covered by income from selling the information updating the system by application of the users and using the services of these institutions.
A distinction is made between the cost of establishing and maintaining the cadastre (e.g. establishment of ALK and ALB) as a one off" cost which is borne by governmental funding. The costs for updating according to applications by or the provision of information from the system for the users is more often based on cost recovery.