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УДК 528:332.4 Gottfried Konecny
Emeritus Professor Leibniz University Hannover, Germany CADASTRAL ISSUES
Introduction
The International Federation of Surveyors FIG has recently stated that about 30 to 50 countries in the world have cadastral systems in operation. Another 50 countries are in the process of establishing one. The remainder of 90 countries do not have a land registry system and they do not have the funds to establish one.
Hernando de Soto has been a primary promoter of land registration systems. His philosophy was adopted by the World Bank and by international donors in support of land registration because secure rights to land not only avoid conflicts, but they also permit to use land as collateral in a widened capital market.
During the last 10 years 1.2 billion $ have been spent on the introduction and the renewal of land registration and cadastral systems.
Most of the problem areas are institutional and political. These issues are not the topic of this paper. But after legal and institutional issues have been solved, technological issues are important to be in a position to rapidly and cost-effectively implement cadastral registration systems.
Purpose of this paper is therefore to discuss the technical alternatives which have been brought about by the recent rapid advances of technology.
Definitions
A cadastre in general is a systematic collection of (spatial) data, which can be queried and maintained. A (land) cadastre in particular is a systematic collection of data on land on a land parcel basis. Such a cadastre consists of two parts: «the book», which contains non-spatial data associated with the parcel and «the map» describing the parcel spatially.
History and Diverse Approaches
The «cadastral book» and the «cadastral map» have been introduced by Napoleon in the early 19th century in Europe as a «tax cadastre». The recording of property rights was obligatory and the description of the property was assured by the map geometry with 1 m ground accuracy.
Starting from the tax cadastre an «ownership protection» cadastre has evolved by about 199, rendering a service to land owners, in which parcel boundaries were monumented and surveyed to cm accuracy. This became practice in Switzerland and Germany.
During the 20th century it was realized that the cm accuracy was only desirable for private purposes, since the public only had an interest in a «spatial data infrastructure» for integrating cadastral with topographic and infrastructure data in form of a «multipurpose cadastre».
The original establishment of a cadastre required an adjudication process, in which the owners of land rights had to state or prove their claims to legal and the survey authorities for a land holding.
The maintenance of the cadastral system required obligatory registration procedures for the transfer of rights on land, which had to be recorded in books, with copies of the book entries in form of land titles.
The ability to maintain a cadastral register depends on the legal practices in use in different countries of the world:
«Private Conveyancing» is used in parts of North America, when land transactions are privately arranged by sales contracts with no security to the purchaser unless he is able to purchase an expensive «title insurance».
Somewhat more secure is a «deed registration», also practiced in North America, where the transfer of land in form of a sales contract is registered at the courthouse and attested by a lawyer or a notary public.
«Title registration» requires the existence of an obligatory registration. The proof of the registration is the title granted to the owner.
In Central European countries there is no need to issue a title, since all valid property rights are registered in the «cadastral book» with the guarantee of the state. The owner can, if needed, request a copy of the book entry.
Requirements for Cadastral Registration
- There must be a unique description of the right (e.g. ownership, lease encumbrance);
- The parcel must be characterized by a unique parcel identifier;
- The person holding the land right must also uniquely identified (e.g. birthplace and date, or social security number);
- Every land transaction must be updated in «near real time» (e.g. at the end of a working day).
Cadastral Maps
In some countries cadastral maps may be useful, but they are not required. In these countries the maps are helpful in identifying the general location of a parcel, but the relative location of the boundaries is described in relative field survey measurements without the need for georeferencing. The map then only serves to identify the parcel, but not its accuracy.
Nevertheless an accurate cadastral map is an asset to a multipurpose GIS, in which cadastre, topography and utilities can be overlaid.
Some cadastral maps also have the disadvantage that they only show the boundaries and the parcels of private owners, but not of the public lands (roads etc.) which lie between them. A multipurpose cadastre must include all land parcels, including those of street sections.
Cadastre 2014
In 1994 the FIG Commission 7 on the Cadastre has drafted a «road map» where the development of the cadastre is developing, under the title «Cadastre 2014» (20 years from then).
Six requirements for the creation and maintenance of a modern cadastre were stated:
- The cadastre should cover all lands (public and private) including all rights and restrictions. Geocoding and a topological boundary structure is a requirement to assure, that parcels do not overlap.
- In a data system there should be no separation between (analog) maps and (analog) registers.
- The use of paper and pen shall be replaced by computer systems to permit automation.
- Cadastral mapping as a standalone activity shall be abolished.
- The public and the private sectors will closely work together in establishing and in maintaining a cadastral system.
- The cadastre will be cost recovering.
Technical Issues
Geocoding
With today’s capabilities geocoding of images, digital maps and survey data should solely be done based on GPS/DGPS. Simple code receivers can only assure accuracies of about 5 m; with corrections transmitted by a service to 2 m. This is sufficient for attribute data collection for an area already mapped for high resolution satellite image data or for orthophoto data.
For a more precise geocoding to dm or even cm level more expensive phase receivers used in RTK mode or in conjunction with CORS systems are required.
The satellite images, orthophotos (or maps) to be geocoded need to be contained in digital raster (or vector) form and they need to be geometrically transformed by shifts, affine, polynomial or least square fitting models to control in a digital workstation.
The images or maps can be loaded in sections (tiles) into a tablet PC or a DPA for use in conjunction with GPS/DGPS) or total station ground surveys. The image or map helps in identification of a point, the survey in the precise coordinate determination.
Adjudication
The adjudication is a process in which the owners of a land parcel present their contracts, deeds or titles to the adjudication team. These documents, if not otherwise available to the authorities, are photographed on site. Then owners and neighbours identify the boundaries of their parcel. They confirm by signature the location of eventually marked and DPPS surveyed boundaries or boundary monuments.
Modern technology permits to send the signed and photographed documents via mobile technology to the field office.
Monumentation
While monumentation of parcel boundaries was an issue around 1900 (in Germany it was made obligatory at that time), coordinate surveys to control via total stations or by DGPS have made reconstruction of a point inexpensive and fast. Monuments are often lost due to construction after a short time. Therefore monumentation now becomes optional, if the client wishes to pay for it.
Surveyed Objects
The basic objects of a cadastral survey are boundary points. Some countries (Germany) do not accept curved boundaries. Curves are realized as chords with the line connecting the boundary points as the actual property limit.
Important are furthermore «permanent» buildings, which in most countries are considered part of the cadastre.
Topographic features are, however, not part of the cadastre. In Germany cadastral maps are at the scale 1:1000. At that scale topography is a value added survey, which is not part of the base data provided by the cadastral administration. Municipalities may contract inclusion of topographic features as value added data to the private sector. This is done for street furniture (parking lots), utilities and trees (tree cadastre). The basic German topographic map is not at the scale 1 : 1 000 but at the scale 1 : 5 000. The AAA concept (AFIS = control monuments; ATKIS = topographic dataset 1 : 5 000; ALKIS = Cadastral basemap 1 : 1 000) attempts to integrate topography with respect to the cadastral base map.
In Britain, the opposite approach is taken. There a basic topographic map is maintained at the scale 1 : 1 200 by the Ordnance Survey, and the Land Register only adds a cadastral layer for its own use.
Maps at smaller scales should use the base map via generalization.
The Ordnance Survey in Britain has committed itself to have an update goal of topography of not more than 6 months.
In Germany the updating of the cadastral basemap is in near real time with the update of the 1:5000 topo maps every 5 years. Due to changes of topography (new construction) this is not fully acceptable, but a remedy is possible by producing digital orthophotos every 2 to 2 ^ years at the scale 1 : 5 000.
Orthophotos may thus be considered as a map substitute which only cost 1/5 of a line map and are producable in 1/5 of the time.
An added advantage is that such orthophotos may be inserted into browsers, such as Google Earth for urban areas, for which Google has an interest and will purchase the products.
Data Models
The basic cadastral data model shall be simple; a land object (parcel) is linked to a certain type of right, such as:
- Ownership for a private parcel;
- Encumbrance for access of an object;
- Building located on a parcel;
- Land use for a parcel or a group of parcels;
- Environmental restrictions for a dfined area;
- Informal status of an object (tribal land).
All objects must be continuously maintained.
The object is geometrically defined in a «map». Preferably this is done in form of shape files with topology. The attributes are linked either directly to the object or they are attached to the defined area via label point.
Otherwise, it is also possible to use CAD geometry without topology. The label point is again the link to the attributes.
Attributes for land objects are stored in a relational database. They contain:
- An application ID for the transaction;
- The application status;
- The status of the workflow (start);
- The date of registration (end).
- The unique parcel ID;
- The type of right (ownership, encumbrance, lease, building, land use, environmental zone);
- The claimant (name, personal ID, % of ownership).
Software needs
Relational Database
Depending on the size of the database may be used
- Access (personal database)
- SQL Server (enterprise database)
- Oracle (enterprise database)
GIS tools
The most widespread use is with ESRI tools, such as ArcGIS (with ArcView for personal database), ArcEditor or ArcInfo via ArcSDE or ArcServer for enterprise database.
Other usable tools are
- Oracle Spatial
- Itnergraph Geomedia
- Bentley’s Microstation and Geographies
- Autodesk’s Autocad Specialized cadastral software
A number of specialized cadastral software products have been developed:
- Arc Cadastre (Swedsurvey) which is not entirely up to date technology
- LM by AED SICAD for European workflows
- ESRI Cadastral Parcel Manage for US and Australian workflows.
Another option is the customization to ArcGIS or other products using local
expertise. This approach has been followed in
- Serbia
- the UK
- Germany
Fast. Low Cost Realization of Cadastral Systems
It has been the experience, that large operating cadastral systems in Central and Northern Europe place their emphasis on maintenance of the records.
In the transformation countries some old cadastral information may exist from the 1940's. In former Soviet areas such information is not available:
In Serbia, Bulgaria, Poland, Albania the task is therefore to superimpose the existing situation contained in satellite images or orthophotos with outdated, not
properly geodetically referenced and perhaps not yet digitized or scanned cadastral maps for an updating process.
In former Soviet controlled areas a new cadastral fabric needs to be created. Particularly in these areas it can be done without the existence of a survey profession, if a group of talented young individuals are trained on new technology, as was done in Georgia.
The trained individuals were able to use the KFW donated equipment forming competing companies managing to establish a cadastral survey system by hightech adjudication in a 5 year period.
In the first year the survey and adjudication cost per pa4rcel was around 10 $. It diminished in the 5th year of operation to 2 $ per parcel.
This shows that the establishment of a cadastral system is possible in the shortest possible time at low cost.
It is now the government’s task to show that maintenance of the system can be done in a sporadic manner.
Low Cost Cadastre
There are a number of possibilities to reduce the cost of a cadastral system.
If there is only one administration in charge of land registration and cadastral mapping (as this is the case in Serbia) duplications of data and mismatches of information can be avoided reducing administrative costs.
The adjudication does not have to be done by survey measurements, as long as the parcel boundaries are identified in satellite images or orthophotos on which they are marked.
If there is a need for a more precise survey due to construction activities (e.g. urban renewal or rural reallocation of parcels) then this could be done on sporadic ad hoc basis.
For the maintenance of the cadastre there are basically 3 scenarios:
Already buildup areas, for which very little changes are anticipated. In these areas sporadic surveys would be used. Modern technology for survey and data base design permit the possibility to improve the originally entered coarse accuracy of 2 m from satellite images or 0.5 m from orthophotos for boundary points to DGPS accuracy of a few centimetres in a sporadic way.
Areas in which new settlements are planned and computer designed on geocoded maps or orthoimages. The computer planned boundary points can directly be staked out by survey instruments in the field using DGPS and total stations. The record of these plans and stakeouts can immediately be used for the content of the cadastral geodatabase.
Rural areas, in which accurate surveys are lacking, and in which combined adjudication - survey procedures are recommended.
No cadastral adjudication and surveys should be undertaken, unless there is a firm commitment by the authorities to maintain the system.
This commitment will also generated trust in the cadastral system, so that it will be used for mortgaging. A secure cadastral system will allow using up to 90 % of the value of the land as mortgage collateral, while unsecure systems may only lend 10 % of the value.
The main requirement is to create a rapid and low cost cadastral system, which should be designed in such a way, that it can be improved by subsequent transactions.
© Gottfried Konecny, 2008
