Cadastral Boundaries Research Articles

Documenting customary land boundaries using unmanned aerial vehicle imagery and artificial intelligence

AbstractThe use of computer vision and deep learning in boundary documentation for land registration stems from the ongoing demand for appropriate mapping approaches of unregistered land rights to eradicate the global challenge of tenure insecurity. Previous research has yielded promising results towards automated extraction of photo‐visible cadastral boundaries from high‐resolution imagery. Nonetheless, the extraction of invisible cadastral boundaries is still a challenge. This study investigates the place of sensor/s on‐board unmanned aerial vehicles and deep learning algorithms in detecting cadastral boundaries. It develops a participatory boundary marking procedure using low‐cost markers to bring monument to previously invisible and ill‐defined cadastral boundaries. After that, the researchers trained and tested the accuracy of a convolutional neural network, namely single shot multi‐box detector (SSD) based on Residual Neural Network (ResNet) and Visual Geometry Group (VGG) backbone networks to automatically detect cadastral boundary markers from unmanned aerial vehicle imagery. SSD based on ResNet34 performed best with 0.88 precision, 0.92 recall and 0.91 F measure or (F1) score. VGG19‐based SSD yielded a precision of 0.47, recall of 0.53 and F1 score of 0.50. The horizontal accuracy of the cadastral map generated varied from 0.089 to 0.496 m per parcel, with a standard deviation of 0.120 m. Results show that this approach is practical for cadastral mapping in rural areas.

CadastreVision: A benchmark dataset for cadastral boundary delineation from multi-resolution earth observation images

Approximately 70%–75% of people worldwide have no formally registered land rights. Fit-For-Purpose Land Administration was introduced to address this problem and focuses on delineating visible cadastral boundaries from earth observation imagery. Recent studies have shown the potential of deep learning models to extract these visible cadastral boundaries automatically. However, studies are limited by the small size and geographical coverage of available datasets and by the lack of information about which cadastral boundaries are visible, i.e., associated with a physical object boundary. To overcome these problems, we present CadastreVision, a benchmark dataset containing cadastral reference data and corresponding multi-resolution earth observation imagery from The Netherlands, with a spatial resolution ranging from 0.1 m to 10 m. The ratio between visible and non-visible cadastral boundaries is essential to evaluate the potential automation level in cadastral boundary extraction from earth observation images and interpret results obtained by deep learning models. We investigate this ratio using a novel analysis pipeline that overlays cadastral reference data with visible topographic object boundaries. Our results show that approximately 72% of the total length of cadastral boundaries in The Netherlands are visible. CadastreVision will enable new developments in cadastral boundary delineation and future endeavours to investigate knowledge transfer to data-scarce areas. Our data and code is available at https://github.com/jeroengrift/cadastrevision.

Location and marking of cadastral boundaries in Nordic countries

Cadastral boundaries are key components for ordering the ownership of real property by dividing it into territories. This study analyses the similarities and differences in marking cadastral boundaries in Denmark, Finland, Norway, and Sweden. A case study was conducted by examining legislations, ordinances, guidelines, and other instructions. These are issued by both the respective national governments, and associated agencies responsible for real property formation and demarcation of boundaries, such as, the national cadastral authorities. We describe, analyse, and discuss the visual division between properties, boundary marks, natural features used as real property boundaries, the information on boundaries in national registers, prescriptive rights, and the localization of boundaries in each country. The outcome of the study shows that there are many similarities between the four countries, but also differences. As an example, the materials used for demarcation differ between each country. Furthermore, the party performing the cadastral procedures range from governmental officials to licenced private surveyors. Finally, differences were noted in whether a real property boundary following a river or stream when created will change position if the river or stream changes course over time.

Furthering Automatic Feature Extraction for Fit-for-Purpose Cadastral Updating: Cases from Peri-Urban Addis Ababa, Ethiopia

Fit-for-purpose land administration (FFPLA) seeks to simplify cadastral mapping via lowering the costs and time associated with conventional surveying methods. This approach can be applied to both the initial establishment and on-going maintenance of the system. In Ethiopia, cadastral maintenance remains an on-going challenge, especially in rapidly urbanizing peri-urban areas, where farmers’ land rights and tenure security are often jeopardized. Automatic Feature Extraction (AFE) is an emerging FFPLA approach, proposed as an alternative for mapping and updating cadastral boundaries. This study explores the role of the AFE approach for updating cadastral boundaries in the vibrant peri-urban areas of Addis Ababa. Open-source software solutions were utilized to assess the (semi-) automatic extraction of cadastral boundaries from orthophotos (segmentation), designation of “boundary” and “non-boundary” outlines (classification), and delimitation of cadastral boundaries (interactive delineation). Both qualitative and quantitative assessments of the achieved results (validation) were undertaken. A high-resolution orthophoto of the study area and a reference cadastral boundary shape file were used, respectively, for extracting the parcel boundaries and validating the interactive delineation results. Qualitative (visual) assessment verified the completed extraction of newly constructed cadastral boundaries in the study area, although non-boundary outlines such as footpaths and artifacts were also retrieved. For the buffer overlay analysis, the interactively delineated boundary lines and the reference cadastre were buffered within the spatial accuracy limits for urban and rural cadastres. As a result, the quantitative assessment delivered 52% correctness and 32% completeness for a buffer width of 0.4 m and 0.6 m, respectively, for the interactively delineated and reference boundaries. The study proposed publicly available software solutions and outlined a workflow to (semi-) automatically extract cadastral boundaries from aerial/satellite images. It further demonstrated the potentially significant role AFE could play in delivering fast, affordable, and reliable cadastral mapping. Further investigation, based on user input and expertise evaluation, could help to improve the approach and apply it to a real-world setting.

Restoration of Land Parcels using Land Consolidation & Readjustment: A Case of Resilience after Flood Disaster

Millions of people are affected from natural disaster leading to loss of land tenure around the world. People affected from the disaster leading to loss of land tenure are often excluded from post disaster assistance. The parcel boundary may change or obliterated because of disaster or also from some infrastructure development. Re-establishing of the cadastral boundary is very crucial and challenging task to re-establish the tenure rights and other cadastral details. This paper focuses on the restoration of land parcels after flood. Paper highlights the impact of flood in parcel boundary and proposes a concept for restoration of those obliterated parcels of Melamchi bazar, Sindupalchok, Nepal which was affected from the flash flood on 15th June 2021. The model for restoration of land parcel using the concept of land consolidation and re-adjustment has been recommended focusing on land pooling, creating a regular shape of the parcel. This paper also evaluates the current legal provisions for restoration of land parcels after land use change due to flood.

Inconsistencies in Cadastral Boundary Data—Digitisation and Maintenance

Most cadastral systems today are coordinate-based and contain only a weak or no reference to measurements or the origin of the information. In some contexts, this is largely due to the transition of land data management and maintenance from an analogue to a digital environment. This study focuses on analysing the importance of the measurement-based cadastre and the digitisation process in North Macedonia and Slovenia. The survey-based boundary data and their integration into the digital environment were not considered in either case study. The positional differences between the survey-based boundary coordinates and the graphical coordinates of the boundaries are significant. The RMSE(2D) for Trebosh was 48 cm, and the RMSE(2D) for Ivanjševci was 56 cm. Consequently, the differences in location affected the areas of the cadastral parcels, resulting in an RMSE of 26 m2 and 23 m2 for Trebosh and Ivanjševci, respectively. These differences can be considered as differences within the cadastral boundary data. Therefore, before harmonising the data between the cadastre and the land register, the inconsistencies within the cadastral data should be eliminated first. The differences in the location of cadastral boundaries and parcel area create new challenges in cadastral procedures (formatting of parcels), conflicts in the relocation of boundaries, and impacts on the land market. The solution lies in the way data is maintained, avoiding duplication of attributes or eliminating inconsistencies (after duplication). Both solutions require further modifications of the legal framework for cadastral procedures related to boundary adjustments and data compliance. This study provides a basis for evaluating inconsistencies in cadastral data and highlights the importance of proper source data selection in the digitization process.

Boundary stones on the border between the Duchy of Styria and the Kingdom of Hungary

Boundary stones are physical markers that identify land borders and above all changes thereto. They are often placed in particularly visible places and inscribed with various kinds of relevant information. They are used for marking borders between countries or between various levels of administrative units within countries as well as for delimiting private landholdings. In the territory of the former Habsburg Monarchy, one can locate many boundary stones that, for example, marked the boundaries of seigniorial, dominical, and church estates as well as administrative and provincial borders. This contribution presents the latter, that is, boundary stones that marked the “Slovenian” section of the border which separated the Duchy of Styria and the Kingdom of Hungary until the end of the First World War, with a particular focus on the wider area of the Municipality of Ljutomer. Although these boundary stones no longer serve their original purpose, in some areas they still coincide with municipal and cadastral boundaries.

Boundary stones on the border between the Duchy of Styria and the Kingdom of Hungary

Boundary stones are physical markers that identify land borders and above all changes thereto. They are often placed in particularly visible places and inscribed with various kinds of relevant information. They are used for marking borders between countries or between various levels of administrative units within countries as well as for delimiting private landholdings. In the territory of the former Habsburg Monarchy, one can locate many boundary stones that, for example, marked the boundaries of seigniorial, dominical, and church estates as well as administrative and provincial borders. This contribution presents the latter, that is, boundary stones that marked the “Slovenian” section of the border which separated the Duchy of Styria and the Kingdom of Hungary until the end of the First World War, with a particular focus on the wider area of the Municipality of Ljutomer. Although these boundary stones no longer serve their original purpose, in some areas they still coincide with municipal and cadastral boundaries.

Boundary stones on the border between the Duchy of Styria and the Kingdom of Hungary

Boundary stones are physical markers that identify land borders and above all changes thereto. They are often placed in particularly visible places and inscribed with various kinds of relevant information. They are used for marking borders between countries or between various levels of administrative units within countries as well as for delimiting private landholdings. In the territory of the former Habsburg Monarchy, one can locate many boundary stones that, for example, marked the boundaries of seigniorial, dominical, and church estates as well as administrative and provincial borders. This contribution presents the latter, that is, boundary stones that marked the “Slovenian” section of the border which separated the Duchy of Styria and the Kingdom of Hungary until the end of the First World War, with a particular focus on the wider area of the Municipality of Ljutomer. Although these boundary stones no longer serve their original purpose, in some areas they still coincide with municipal and cadastral boundaries.

Revising Cadastral Data on Land Boundaries Using Deep Learning in Image-Based Mapping

One of the main concerns of land administration in developed countries is to keep the cadastral system up to date. The goal of this research was to develop an approach to detect visible land boundaries and revise existing cadastral data using deep learning. The convolutional neural network (CNN), based on a modified architecture, was trained using the Berkeley segmentation data set 500 (BSDS500) available online. This dataset is known for edge and boundary detection. The model was tested in two rural areas in Slovenia. The results were evaluated using recall, precision, and the F1 score—as a more appropriate method for unbalanced classes. In terms of detection quality, balanced recall and precision resulted in F1 scores of 0.60 and 0.54 for Ponova vas and Odranci, respectively. With lower recall (completeness), the model was able to predict the boundaries with a precision (correctness) of 0.71 and 0.61. When the cadastral data were revised, the low values were interpreted to mean that the lower the recall, the greater the need to update the existing cadastral data. In the case of Ponova vas, the recall value was less than 0.1, which means that the boundaries did not overlap. In Odranci, 21% of the predicted and cadastral boundaries overlapped. Since the direction of the lines was not a problem, the low recall value (0.21) was mainly due to overly fragmented plots. Overall, the automatic methods are faster (once the model is trained) but less accurate than the manual methods. For a rapid revision of existing cadastral boundaries, an automatic approach is certainly desirable for many national mapping and cadastral agencies, especially in developed countries.

Managing Inhomogeneity in the Control Point Network during Staking Out Cadastral Boundaries in Austria

The coordinate system of the Austrian cadastre is physically realised through control points provided by the national institution for surveying. Due to historical development over the centuries and changes in measurement technologies, inhomogeneities can occur within the local control point network. These inhomogeneities affect the derived boundary point coordinates. When staking out boundary points in an area with inhomogeneous control points, deviations from the boundary marks in the field can occur that exceed the accuracy requirements of the ordinance for surveying. Examples show that a suitable approach to tackle this issue has to be selected on a case-based strategy. Different situations might require different approaches. This needs to be considered in the legal framework to enable cadastral experts to select the optimal approach.

The new, LADM inspired, data model of the Dutch cadastral map

The Netherlands’ Cadastre, Land Registry and Mapping Agency – in short Kadaster – provides legal certainty about every piece of land (and water) in the Netherlands. Newly surveyed cadastral boundary geometry is documented in land surveying field sketches and processed in the nationwide cadastral map. Because of the different working methods since the start of cadastral surveying in 1811 (a nationwide cadastral map was available in 1832 when Kadaster was established) the map has a so-called graphical quality. The standard deviation of boundary points is 20 cm for urban areas and 40 cm for rural areas (in the national reference system), this implies that the geometric quality of the current map is insufficient for determining the exact parcel location in the field. With an increasing digitization and open data policy, multiple sources of information (including the cadastral map) are demanded to be accessible and usable by a wide range of users. This so-called geographical quality and its limitations leads to bottlenecks and incomprehension. This is the reason why Kadaster has started a program, the Cadastral Map Next program, aiming at the development of a methodology for the development of a new version of the cadastral map. The aim of this new version is that the location of boundaries is so accurate, that the boundary coordinates from the map are usable for a better approximation of the boundary location in the field and can accommodate future demands and developments. This development process is based on the use of the original field observations. For this purpose, almost all observations on all (historical) field sketches must be processed. There are about 5 million digitally archived field sketches. This is an enormous challenge that requires far reaching automation. The program has investigated whether it is possible to automatically extract the original (mostly handwritten) measurements from the field sketches and to combine this information and re-determine the location of the boundaries with a very high accuracy of boundary points. With the support of several companies, it has been possible to build a cadastral map with a known geometrical quality and verified accuracy. This accurate cadastral map is called ‘Reconstruction Map’, a working title for the cadastral map with known geometrical quality and higher accuracy. Once this map is ready and the involved parties agree, it will be introduced and presented as the ‘Cadastral Map Next’ and replace the current cadastral map. An important step in this process is to redesign the current data model from parcel level to the more specific boundary level to achieve an unambiguous connection between cadastral objects and its related survey data. A challenge in this process is that the current survey documents only describe changes in a parcel, thus different boundaries of a parcel are related to different survey documents. This challenge should be addressed in the new model. The new data model applies the sub-package ‘Survey and Representation’ of the Land Administration Domain Model (LADM), an ISO standard, for solid solutions in their design process. The basic structure of spatial sources, points, boundaries and parcels, all with their own identification, enables to store relevant data, like coordinates, quality descriptions and metadata, as attributes to these objects. Further new relations can be established while previous ones are maintained. The concept of the ‘Reconstruction Map’ and the ‘information layer’ (metadata) will bring new insights to establish new relations and so relate the different cadastral objects in a more dedicated way.

Success factors in cadastral boundary settlements based on land surveyor’s opinions

The purpose of this research was to theoretically and empirically explore the success factors in cadastral parcel boundary settlements. Our focus was to study the role of landowners in boundary settlements and dispute management. The issue of landowners’ involvement is highly topical and complex, as the number of disputes stemming from indeterminate landowners’ roles in managing cadastral boundaries and indeterminate roles of the land surveyor as the mediator are considerable. These disputes can be a heavy burden for the country and society as a whole. Our basic research question was very widely set so that the model of success factors of boundary settlements following land cadastre data would go beyond the geodetic and legal framework and would also cover socio-psychological factors. In the literature, this topic is still not addressed, although there are several scientific questions related to it, the focus being on the integration of sociological and psychological factors into the field of spatial management. Based on the opinions of authorised land surveyors, we found for the case of Slovenia that the success of boundary settlement is, along with engineering and property aspects, also influenced by socio-psychological factors. The following factors were found to be essential: previously marked boundaries, preliminary analysis, clear explanation, surveyor’s expertise and communication skills, neighbourly relations between landowners, (psychological) attachment to land, and other personality traits of landowners. Generally, it was found that the surveying procedure and the land surveyor are the most important factors of success in boundary settlements, closely followed by the landowner, while the land data (cadastral data) is the least important factor. We also found that the land surveyor influences the landowner and how the factors related to the landowner will reflect upon the success of the boundary settlement; this confirmed that the land surveyor and the landowner are the most important factors of success in cadastral parcel boundary settlements.

Nagydobrony és a Nagydobronyi Vadvédelmi Rezervátum (Kárpátalja) földrajzinévtárának elkészítése és ábrázolása történeti térképek alapján

The Wildlife Reserve of Velyka Dobron – which is located next to the village of Velyka Dobron (Hungarian: Nagydobrony), the fourth most populous Hungarian community in Transcarpathia – is the third-largest protected reserve of national importance in the country. We used a Geographic Information System to process and map the historical geographical place names of the settlement and the protected area (pieces of land within the cadastral boundaries but located either outside the settlement boundary or on its outskirts) based on the 1st, 2nd and 3rd military surveys, a cadastral map dating back to 1865 and the documents available in the Beregszász branch of the State Archives of Transcarpathian Oblast (fonds 125, description 6, file 344), as well as literary materials. As a result, a database comprising a list of 57 place names of the area was compiled. Likewise, a map of the pieces of land within the former cadastral boundaries and in the Nagydobron’ Wildlife Reserve was made. Analysis of forest area and land use changes showed that 16 pieces of land within the cadastral boundaries, but located either outside the settlement boundary or on its outskirts, have completely lost their former nature and as a result became part of the inner area of the settlement. Consequently, the compiled database and maps may help to specify the location of the ongoing research and clarify the accurate place of the earlier studies.

A BIM-IFC Technical Solution for 3D Crowdsourced Cadastral Surveys Based on LADM

In most countries, three-dimensional (3D) property units are registered utilizing two-dimensional (2D) documentation and textual description. This approach has several limitations as it is unable to represent the actual extent of complicated 3D property units in space. As traditional procedures often lead to increased costs and long delays in 2D cadastral surveying, a fast, cost-effective, and reliable solution is needed to cope with the remaining global cadastral surveying needs. Crowdsourcing has claimed a critical role as a reliable methodology with huge potential regarding the realization of 2D and 3D cadastral registration in both an affordable and a timely manner. Many large modern constructions are now planned and constructed based on BIM technology all over the world. The utilization of 3D digital models, such as building information models (BIMs), and the establishment of a connection with the international standard of the Land Administration Domain Model (LADM) could be a solution for the rapid integration of these units into a 3D crowdsourced cadaster with a better representation of the cadastral boundaries of these units, a detailed visualization of complex infrastructures, and an enhancement in the interoperability between different parties and organizations. In this paper, the potential linkage between the BIM, the LADM, and crowdsourcing techniques is investigated in order to provide an effective technical solution for the integration of large new constructions into 3D crowdsourced cadastral surveys. The proposed framework is tested on a building block in Athens, Greece. The potential, perspectives, and reliability of such an implementation are assessed and discussed.

Deep Learning for Detection of Visible Land Boundaries from UAV Imagery

Current efforts aim to accelerate cadastral mapping through innovative and automated approaches and can be used to both create and update cadastral maps. This research aims to automate the detection of visible land boundaries from unmanned aerial vehicle (UAV) imagery using deep learning. In addition, we wanted to evaluate the advantages and disadvantages of programming-based deep learning compared to commercial software-based deep learning. For the first case, we used the convolutional neural network U-Net, implemented in Keras, written in Python using the TensorFlow library. For commercial software-based deep learning, we used ENVINet5. UAV imageries from different areas were used to train the U-Net model, which was performed in Google Collaboratory and tested in the study area in Odranci, Slovenia. The results were compared with the results of ENVINet5 using the same datasets. The results showed that both models achieved an overall accuracy of over 95%. The high accuracy is due to the problem of unbalanced classes, which is usually present in boundary detection tasks. U-Net provided a recall of 0.35 and a precision of 0.68 when the threshold was set to 0.5. A threshold can be viewed as a tool for filtering predicted boundary maps and balancing recall and precision. For equitable comparison with ENVINet5, the threshold was increased. U-Net provided more balanced results, a recall of 0.65 and a precision of 0.41, compared to ENVINet5 recall of 0.84 and a precision of 0.35. Programming-based deep learning provides a more flexible yet complex approach to boundary mapping than software-based, which is rigid and does not require programming. The predicted visible land boundaries can be used both to speed up the creation of cadastral maps and to automate the revision of existing cadastral maps and define areas where updates are needed. The predicted boundaries cannot be considered final at this stage but can be used as preliminary cadastral boundaries.

DESIGNING ENVIRONMENTALLY HAZARDOUS OBJECTS BY MEANS OF GEOGRAPHIC INFORMATION SYSTEMS

The article deals with the current problem of solid waste disposal. Also the use of geoinformation technologies in the design of environmentally hazardous facilities. The sequence of actions in case of reconstruction of a land plot for the construction of a solid waste landfill is described in detail. It shows how you can use geographic information systems to speed up and better accomplish the task. The convenience of using geographic information systems when planning such tasks is obvious. It is advisable to use geographic information systems when planning environmentally hazardous facilities. This is due to the complex nature of the problem. This requires the involvement of additional spatial data. It is the geographic information system that will allow the use of all data in the complex based on the principle of their spatial position. You can also use data models to support the creation, validation, and correction of information. In a geographic information system, you can create a geodatabase. This will create a 3D model of a solid waste landfill. The 3D model allows you to better represent the terrain. Creation of a triangulation network will allow to correlate all layers created in the geodatabase. The triangulation network is created from 3D terrain points. It allows you to get a three-dimensional model of a high-altitude polygon. This provides many possibilities in the future. It will be possible to interpret 3D models with high-precision engineering systems. This allows you to carry out any geometric measurements, build sections and profiles, as well as monitor activities at the solid waste landfill. Based on these data, it is possible to measure the volumes of household waste, areas, the height of the landfill in terms of the height of the actual relief and the level of groundwater, the altitude characteristics of the landfill and slopes to compare them with the standard indicators. The three-dimensional model will make it possible to identify inconsistencies between the actual boundaries of the polygon with the cadastral boundaries of the site allocated for these purposes. With the help of geographic information systems, simplicity, speed and clarity in the formation of conclusions and decision-making will be provided.

Crustal Deformation Across and beyond Central Europe and Its Impact on Land Boundaries

Land is a critical and limited natural resource. The Land Administration System (LAS) has been developed to resolve and adjudicate over any disputes that might arise concerning the rights and boundaries of land. Land registration and cadastre are types of land recording that need to be established. To secure the property rights, we must be sure of accuracy of the boundary points determining the size of the property. However, in addition to typical factors considered when determining the boundary point positions, such as accuracy of geodetic networks and measurement errors, the global and local crustal deformation, resulting, e.g., from the movement of tectonic plates, should be considered. In this work, the focus is on the movement of points inside the European plate due to tectonic movement, without taking into account local events caused by erosion, landslides, etc. The study area is Europe, and particular attention was paid to Poland, which is located in the centre of the European continent and does not have significant anomalous sub-areas, making it an authoritative research object. In this study, we analysed the velocity of point displacements and the boundary deformation, using GPS observations. For this reason, we used both global (IGS) and regional (ETRF) reference frames, to show differences in point velocities for the studied areas. Overall, for the needs of the real estate cadastre in Poland, information about parcel boundary points must be obtained with an accuracy better than 0.30 m. Within 25 years, the border mark may be shifted by 0.13 m due to tectonic plate movement, which is within the required accuracy. Pursuant to the current legal regulations, the measurements of the boundary points can be performed with any method, ensuring the required accuracy (0.30 m). The most commonly used are direct measurements (GNSS and tacheometry) and photogrammetric measurements. It is recommended that periodic verifications and update of the cadastre data in Poland be carried out at least once every 15 years. In the case of such relatively frequent verification and possible modernisation of data, the potential impact of tectonic plate movement on the relative boundary point displacement can be ignored, particularly in the short term. However, for a long time period it has an influence. We suggest “relatively frequent” cadastral boundary verification to be able to ignore such influence.

Bi-temporal foundation for LADM v2: Fusing event and state based modelling of Land administration data 2D and 3D

The prime purpose of Cadastral data – whether in the form of maps, survey plans or notes, or a digital database is the definitive demarcation of the extent of properties – and can be seen primarily as a decision support facility (“Can a structure be built here?”, “Where can I build a fence?”, “Should I buy this property”?). There are, however many additional uses for which this information has been applied – such as a base for the recording of assets such as light poles, underground cables, etc. and as a history of the pattern of land use and subdivision. Although secondary, these uses are important, and should be adequately supported including the historic information.It is a fact that the determination of cadastral boundaries can only be carried out to a certain accuracy, and that that accuracy has been improving over time. Older surveys had been carried out with limited positional control, and using equipment with a low intrinsic accuracy by modern standards, although they correctly represent the topology between properties. As a result, later surveys provide an opportunity to improve the positioning of existing boundaries data without disturbing the topology of the existing data. In addition, engineering works such as road building, can provide a source of high accuracy position data that can be applied to improve low accuracy existing data.This argues that the accuracy of boundaries should be improved in the historic record of the cadastre – after all we would like to see our historic parcels in the position we now know them to have been, so that they are comparable with current boundaries. Likewise, we need to correct inaccuracies in the attributes of the spatial objects and the topology between them (e.g. which spatial units are adjacent to or near a given object).On the other hand, we must not lose sight of the decision-making side of the requirements – so that a past decision can be reviewed in relation to the data as it existed then. If the current knowledge in the database of today is used to review old decisions, they may seem irrational.Data custodians are well aware of this issue, using terms like “update” to indicate a “real-world” change, while using “upgrade” to indicate an improvement of the database representation not accompanied with a change “on the ground”; however database software has not carried this knowledge through – resulting in its loss.This argues for a database with bi-temporal history – where our current best knowledge of the history of the cadastre is recorded, and that history is corrected and maintained, while our past knowledge of the data also recorded as an audit trail (so that we can ask questions like “what did we in 2017 think the definition of this property was in 1994?”). This is realized via two types of time: database (or system) time and real world (or valid) time.The different historic records, combined with changes of datum, can lead to confusion in terminology – where words such as “point”, “position”, “boundary” become overloaded. This paper is intended to provoke discussion of terminology to clear up this confusion, and potentially to assist with an extension of the temporal model as input for the revision of LADM to accommodate bi-temporality.

High-Quality UAV-Based Orthophotos for Cadastral Mapping: Guidance for Optimal Flight Configurations

During the past years, unmanned aerial vehicles (UAVs) gained importance as a tool to quickly collect high-resolution imagery as base data for cadastral mapping. However, the fact that UAV-derived geospatial information supports decision-making processes involving people’s land rights ultimately raises questions about data quality and accuracy. In this vein, this paper investigates different flight configurations to give guidance for efficient and reliable UAV data acquisition. Imagery from six study areas across Europe and Africa provide the basis for an integrated quality assessment including three main aspects: (1) the impact of land cover on the number of tie-points as an indication on how well bundle block adjustment can be performed, (2) the impact of the number of ground control points (GCPs) on the final geometric accuracy, and (3) the impact of different flight plans on the extractability of cadastral features. The results suggest that scene context, flight configuration, and GCP setup significantly impact the final data quality and subsequent automatic delineation of visual cadastral boundaries. Moreover, even though the root mean square error of checkpoint residuals as a commonly accepted error measure is within a range of few centimeters in all datasets, this study reveals large discrepancies of the accuracy and the completeness of automatically detected cadastral features for orthophotos generated from different flight plans. With its unique combination of methods and integration of various study sites, the results and recommendations presented in this paper can help land professionals and bottom-up initiatives alike to optimize existing and future UAV data collection workflows.