Abstract

Located in the midst of geographical Europe, in Southern Transylvania / Romania and surrounded by the Carpathians, the Transylvanian Saxon fortified church landscape as a unique diverse traditional, very local and natural landscape has survived and withstood the political, economic and cultural changes of the centuries. The region is outstanding by a unique built heritage which is embedded in a landscape which has been characterized by a flourishing agriculture in the past. In the end of the 20th century lot of inhabitants were emmigrated from Romania and immigrated to Germany which led to the abandonment of this region. With the disappearance of the Protestant rural communities, the fortified churches lost their importance as a place of identification and lost their preserver also. Therefore, the maintenance of these fortified churches is a challenging task for the evangelical church A.B. Romania as the owner. One of the typical problems thereby is the lack of as-built documentation and plan drawings. This report shows that in which short time but with enthusiastic and schooled people such documents can be created, giving a basis for future maintenance and restoration work.

Keywords:Construction Survey; Fortified Church; Building; Landscape

Introduction

The fortified church of Apold

The Transylvanian Saxon fortified church landscape includes more than 150 fortified churches that still exist but also the village with their traditional farm houses. The surrounding landscape is characterized by an extensively cultivated agriculture and an intact nature. Both, nature and architectural heritage are protected by different levels, UNESCO and Natura 2000. The land became an attractive settlement area from the 12th century for German, French and Flemish farmers, craftsmen and traders. They received extensive privileges, such as freedom and autonomy as well as duty to defend the Hungarian king. The fortified churches were designed and extended in such a way that could be used both as a place of religious mass and as well as a last refuge. Together more than 300 fortified churches were built from the middle of 15^th century to the 18^th century. After the loss of their defence function, many parts of the fortified churches fell into decay or were even demolished [1].

The Apold fortified church is one of the largest building ensembles of its kind of this region of Southern Transylvania (Figure 1). The history of the ten obtained building units stretches over seven centuries. In the beginning of the 13th century with the construction of the Romanesque basilica with three naves and no tower were built. The invasion and devastation by the Mongol armies during the years 1241/42 led to the construction prompted the parish of a curtain wall and a west tower which was integrated into the church. Favoured by royal privileges and the autonomy of the Transylvanian Saxons, the rural communities in Transylvania grew into bourgeois towns with rights for markets and trade. This prosperity and the new gothic architectural style led to an initial rebuilding: the Romanesque subdivision was broken up, the outer walls of the side aisles were raised and a hall with four octagonal columns and groined vaults were built in the central nave. The third construction phase 1504-1507 included mainly the fortification. The church obtained a further defence floor and the west tower was raised and strengthened with a defence corridor anda wooden battlement. Over the next two centuries, the fortified church complex was extended by two towers and a fruit house for storing supplies. Starting at the end of the 18^th century, the fourth construction phase was characterised by the loss of the fortifications and rebuilds. Due to the large-scale emigration of the Transylvanian Saxons in the early 1990s, the fortified church was affected by rapid decay and theft [2,3].

Maintenance and restoration of the fortified church

The CasApold association, founded in 2007, has set itself the goal of researching, restoring and repurposing this fortified church based on the developed conservation- and use vision. With few financial resources but a lot of voluntary commitment many emergency and repair measures were performed and the decay of the fortified church has been stopped. In addition, since 2009, workshops, handicraft and architecture courses, cultural events as well as expertises in monument heritage preservation were done. In the future CasApold intend to build up a Research and Education Center for Fortified Churches, where experts can meet, exchange and take part in preserving these unique culture landscape.

An enormous difficulty for the preservation and restoration of the fortified church landscape is the lack of as-built documentation and plan drawings. The CasApold association therefore came up with the idea of organising a summer school focusing on digital building surveys and the development of conversion concepts. In the international summer school, organised in 2022, the CasApold association, the Fortified Churches Foundation, the study programme of Digital Technologies in Heritage Conservation of the University of Applied Sciences Coburg and University of Bamberg, the study programme of Architecture of the Polytechnic University of Timisoara as well as the Europe-University Viadrina in Frankfurt/Oder were involved.

Concept of the construction survey performed during the summer school

For a fast capture of the entire fortified church area, in particular the rampart wall, the surroundings buildings, but also those building elements that are more difficult to access, such as the roof or the staircase in the church tower, a ZebHorizon laser scanner from GeoSLAM was used. The mobile laser scanner is carried by hand which gives the user a high degree of mobility. The coordinates are determined by the scanner knowing its own relative position in space. In order to obtain successful scans, a track should be planned in advance so that the scans can be completed in loops.

In addition, for more accurate scans with higher resolution for the church building the laser scanner P40 from Leica was used. After planning the individual scan positions which have to ensure sufficient overlap between the individual scans and the architecture forms different acquisition settings were made on the laser scanner. The scan resolution was selected in the range from 50 [mm@10m] to 0.8 [mm@10m]. Depending on the requirements, the individual scans can be also performed with color information. Once the registration of the individual scans has been completed (using the method cloud-to-cloud), the entire point cloud can be aligned to the fixed point network using the detected target markers.

Different wall paintings and architectural details were assessed using the Structure from Motion (SfM) procedure. It describes a process that makes it possible to generate a 3D model of an object using overlapping photos. For that, the full-frame Sony Alpha7R camera with a 55m fixed focal length lens was taken for the work. The images were photographed with an overlap of 60%.A total station was used to measure control points, which has been taken to generate a scale in order to create an orthoimage. These markers were also necessary to orientate the image in the model of building.

The fortified church stands on a cohesive subsoil characterised by a mixture of sandstone and limestone mortar. Some buildings of this ensemble are showing settlement cracks. For a monitoring of the churches movements a fine levelling using the Leica LS15 with an accuracy of 0.4mm was applied.

For each of applied measurement methods, the recorded data are orientated by registration and transferred to its own local coordinate system. However, these are not aligned with each other or with the entire ensemble and must therefore be merged into a superordinate, global measurement net system (Figure 2 & 3). This then also allows transfer to a supra-local global coordinate system such as the UTM system (Universal Transverse Mercator). For the transformation into the global measuring system, the targets are designed in a way so that coordinates of every used measuring system applying the Leica TS 07 total station were recorded (Figures 2-4).

Results

The post-processing of the scan data and images for the SfM process was carried out during the summer school. These were later used as the basis for drawing the site plan of the fortified church including the surrounding terrain at a scale of 1:600, the floor plans of the church at various height levels, the cross-sections in the nave (Figure 5) and tower and the longitudinal sections at a scale of 1:150. As a further result, different orthoimages of medieval wall paintings and special architectural details of the church were created (Figure 6). They have a high resolution of 0.2 mm and are ideal for documentation purposes. The summer school was complemented by a structural analysis of the fruit house, an architectural history study of this ensemble and two restoration workshops.

On the basis of the existing measuring grid, the measurements can be repeated at any time and a discontinuous monitoring system has been introduced.

This building survey was carried out by an international team of lecturers and students from various universities in Europe. In the short time of a summer school, various planning documents were created, making a significant contribution to the preservation of the fortified church in Apold in the future.

Acknowledgement

Special thanks go to the German Federal Government for Culture and the Media for their financial support. The CasApold association for their support for this research gratefully acknowledged.

References

1. Bethge S (2002a) The Transylvanian-Saxon landscape of fortified churches – a historical and monument preservation journey in: Apold Heritage Lab - Summer school for monument conservation in Transylvania / Romania, p. 8-9.
2. Bethge S (2002b) The fortified church of Apold in: Apold Heritage Lab – Summer school for monument conservation in Transylvania / Romania, pp. 14-15.
3. Fabini H (2022) Atlas der siebenbürgisch-sächsischen Kirchenburgen und Dorfkirchen Band 2, third edition, Schiller Verlag.