Topography changes from the Middle Ages to the Present in the Area of the Palatium of Ingelheim
Matylda Gierszewska
This MSc thesis is submitted in the framework of and according to the requirements of the UNIGIS Master of Science Programme
(Geographical Information Science & Systems) 2010
This MSc thesis was carried out under the supervision of dr hab. Jacek Kozak Jagiellonian University of Kraków, Paris-Lodron University of Salzburg
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2 I declare that all sources used in this paper are listed in accordance with the rules of citation. This work was done independently. This work was not and will not be submitted as a thesis in another institution.
Ingelheim, 20 December 2010 Matylda Gierszewska
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3 Contents
1. Introduction...5
2. Purpose and scope of the research...7
3. Study area and chronology...8
4. Historical background...12
5. History of the research...15
5.1. Archaeology and architecture...15
5.2. Discussion of terms – DEM/DTM and study on the Historical Digital Terrain Model...18
6. Data sources...22
6.1. Sources of spatial data...23
6.1.1. Archaeological documentation...23
6.1.2. Architectural documentation...25
6.1.3. Cartographic sources...26
6.1.4. Terrain measurements...27
6.2. Sources of non spatial data...27
6.2.1. Archaeological documentation...27
6.3. Cartographic projection and local reference systems...28
6.3.1. Cartographic projection – Gauss-Krueger...29
6.3.2. Local reference systems...30
7. Methods...32
7.1. GIS technology and software...32
7.2. Data processing and analysis...33
7.2.1. Elevation data...34
7.2.1.1. Selection of the preliminary set – standards for selection of the data and their structure...34
7.2.1.2. Preparation of the data for particular models – selection of the representative set...38
7.2.2. Barriers...40
7.2.2.1. Selection of the preliminary set and the georeference of the plan from Marksburg...40 7.2.2.2. Preparation of the data for the particular models – selection of
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4
the representative set...44
7.3. Quality control of the data and errors in their acquisition...45
7.3.1. Control of the errors made during the archaeological excavation and errors of the data...47
7.3.2. Control of the errors in interpretation of archaeological features..48
7.3.3. Control of the errors related to the lack of archaeological information...48
7.3.4. Control of the georeference errors and their verification...48
7.3.5. Control of the digitization errors and their generalisation...50
7.3.6. Control of the measurement errors...51
7.4. Interpolation...51
7.4.1. Trial interpolations on the single data set and selection of a particular method...53
7.4.2. Errors of trial interpolations and the subjective - visual evaluation...57
7.5. Comparative analysis of the DTMs...59
7.5.1. Analysis using map algebra...59
7.5.2. Comparison of cross sections...61
8. Results...63
8.1. Errors of data and errors made during primary operations on the data...63
8.2. Data sets for modelling...66
8.3. DTMs and evaluation of interpolation accuracy...70
8.4. Results of comparative analysis of the DTMs...74
9. Discussion...87
9.1. Usefulness of the research and the value of the applied method...87
9.2. Topography changes from the Middle Ages to the present in the Palatium...91
10. Conclusions...93
11. Bibliography...96
12. List of illustrations...106
13. List of tables...109
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5 1. Introduction
The term topography comes from the Greek language, topo- means “place” and graphi- means “describing”, therefore, it is a section of geography and the study of the shape and surface features of the Earth. In a broader sense it also determines the local elements; including the relief of the terrain, vegetation, anthropogenic features, and even the local history and culture. (Topography 2001 – 2010, 2010)
The word palatium comes from Latin and originally meant “a hill” on which the Roman emperors, starting with Augustus, had their residence. From the Early Middle Ages this name has defined a ruler’s habitat which has a representational character (Pfalz, Palast 2002). It was not a permanent residence of reigning. In the times of a mobile way of governance, the king or emperor was forced to move between his palaces. In this paper the following term of the palatium will be used – namely a residence, palace and foundation.
The topography of the palatium in Ingelheim has been mainly formed by human impact. There were more intensive changes associated with an extension of the whole area of residence and a minor renovation inside a single building. Only great transformations were included in this research, whereas the slightly changes were excluded. Natural elements, such as a slope/inclination or exposition, are visible in the present terrain form as well as in the reconstructions for all periods. In this study, attempts were made to combine the two elements of the residence landscape, i.e.
anthropogenic and natural. The methods which were used in this research include a natural slope of the area and simultaneously sharp boundaries of the different buildings of the palace. Also, the dynamics of changes in the particular buildings of the residence, which are of anthropogenic origin, play a significant role in the study. This issue was described in two manners, namely as a spatial feature and as a qualitative change over time. The research area is confined to the territory of the palace. The time frames are designated within the foundation of the residence and the contemporary situation of this area.
The Geographical Information System proved to be a great “tool” in visualising and carrying out an analysis of the topography changes of the palace in Ingelheim. This system was applied at almost every stage of the research; starting with collecting data in a database, which was prepared for this project, through selecting the test methods,
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6 conducting them and with the final presentation of the results with maps. The methods used by archaeologists and the processes which are characteristic for GIS were
connected and used in this study. This provides an interdisciplinary approach to the topic and stresses the important role both these sciences and their interdependence play.
The first chapters of this study are devoted to general issues, namely the purposes and research area, the chronological framework and historical background.
The archaeological excavations which took place in the area of the residence, as well as attempts to create Historical Digital Terrain Models were described in the history of the research. This description is supplemented by an explanation of the used terms, such as DEM and DTM.
One of the main parts of the paper is devoted to the sources, their character and the way they were collected. Due to the multitude of different local reference systems and map projections this problem was discussed as a separate chapter. The methods, verification of data and creation of the preliminary and representative set of data have a central focus in this study. A description of the errors that may occur at various stages of the research is also included in the work. This paper concludes with the results and a discussion which outlines relevant findings and perspectives for these studies.
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7 2. Purpose and scope of the research
The main aim of this paper is to restore the historical topography of the palatium in Ingelheim – understood as a historical utility level – using tools available in a
Geographical Information System (GIS). In addition to the Historical Digital Terrain Model (DTM), representation of the contemporary surface of the research area was presented.
The developed models were compared and the differences between the particular building phases of the palatium were calculated using map algebra. Subsequently, the size of the transformation area was appointed, which was one of the targets of this work.
Also, another way of analysis is briefly presented, namely collation of the cross sections of the terrain generated from DTMs.
A further goal of this research is to develop a method of generating the Digital Terrain Model of a historical anthropogenic landscape. This was the main part of the presented study. The investigation contains the method of preparatory work, namely data collection, which focuses on archaeology, as well as a part of research carried out in GIS, namely georeference, interpolation, data validation and comparative analysis.
These objectives were achieved through the collection of height information from archaeological excavations which were carried out between 1909-2009 and their interpretation, measurement of the contemporary surface, georeference of the plan from Marksburg and reconstruction of the historical buildings in the palace.
The creation of the 2.5 D DTMs visualisation was essential to clarify the results of the interpolation. This was fundamental to determine the methods for model
generation and for a distinction of the areas of interpolation errors. The DTMs were the base outputs for the comparative analysis carried out by using map algebra and cross sections of the terrain.
Also the efficacy and usefullness of this method was proved both during performance of singular models and over the comparative analysis.
A critical approach was an important element at each stage of the research, either in the data collection, interpretation or executed analysis.
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8 3. Study area and chronology
The city of Ingelheim is located in the south-western part of Germany, in the state of Lower Rhineland-Palatinate, in the district of Mainz-Bingen (Fig. 3.1, 3.2).
Fig. 3.1. Map of Germany and location of the city of Ingelheim
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9 Fig. 3.2. Location of the palatium in Ingelheim (DTM made with SRTM data)
The study area covers the territory of the so-called Saalgebiet (area of the Saal) in Ingelheim on the Rhine, in the city district – Lower-Ingelheim [ger. Nieder-
Ingelheim]. The investigation area is limited within the following streets:
– from the south: the street Zuckerberg [ger. Zuckerberg]
– from the west: the square François-Lachanel and the street Natalie von Harder [ger.
François-Lachenal-Platz and Natalie von Harder-Strasse]
– from the north: the street Natalie von Harder and Auf dem Graben [ger. Natalie von Harder-Strasse and Auf dem Graben]
– from the east also the street Auf dem Graben. [ger. Auf dem Graben]
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10 Fig. 3.3. Area of the Saal and the palatium
in the city of Ingelheim on the Rhine
The research area is historically associated with the reign of the Carolingian dynasty and with the palatium that was founded on this site in the 8th century. The primary residence of the emperor was confined to the northern part of this territory. In the 12th century it was extended in the southern direction by the Staufen dynasty.
Presumably, Frederick I Barbarossa was the initiator of the extension of the palace (Fig.
3.3, 3.4).
The area of the residence in its first phase of development was 21,438.5 m², in the 12th century it increased to 38,549.75 m² with a surrounding moat. The area of the research varied depending on the examined historical period. It was increased in the 4th phase due to an enlargement by the Hohenstaufen dynasty.
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11 The chronological range includes the Middle Ages, and the exact moment of the foundation of the palatium in Ingelheim in the 8th century to the present.
The Digital Terrain Models were interpolated for the following phases of the building development in the research area:
1. The moment of preparation of the terrain for the building of the palatium – 8th century
2. Carolingian phase – 8th/9th century
3. Ottonian and Salian phase – 10th and 11th century 4. Staufen phase – 12th century
5. Modern phase – c. 19th century/20th century. This phase was removed from the investigation, which will be explained in a further chapter of this paper.
6. Present – 21st century
Initially, data for the 19th and early 20th centuries were incorporated into the study but the lack of information and convergence with the present data resulted in their exclusion.
Fig. 3.4. Palatium in Ingelheim, the building phases and main constructions
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12 4. Historical background
Fig. 4.1. Portrayal of the city of Ingelheim and the palatium in Cosmographia by Sebastian Münster (1550)
(Historischer Verein Ingelheim 2008)
The palace of Ingelheim was founded in the middle terrace of the Rhine which is located above the flooded area. Historical sources date the beginnings of the residence building to the end of the 8th century. Charlemagne’s first visit has been dated to the year 787 and 788, which is mentioned by Einhard, the ruler’s chronicler (Grewe 1998).
During Charlemagne and his successors’ reign the main expansion of the residence took place. At this time the two largest architectural constructions were built, namely the aula regia, the north hall and the exedra, a semicircular building with a columned passage.
The north and south borders of the palatium were also determined as two parallel sections. The church with its three apses or conches was built in the central part of the foundation (Grewe 1998, 1999, 2001, 2006, Grewe et al. 2001, Wengeroth-Weimann 1973). Charlemagne as well as his successors appreciated this place, e.g. Louis the Pious visited the palatium in Ingelheim about ten times (Archäologie 2005-2009).
Another period of the residence’s expansion is associated with the reign of two dynasties, namely Ottonian and Salian. During this period the palace experienced its renaissance. At this time small transformations took place inside the buildings erected by the rulers. Larger changes are related mainly to the sacral architecture. In the 10th
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13 century the church in the cross form, the so-called Saalkirche, was built. Before the year 900 an inconsiderable church with three apses in the middle of the residence was rebuilt into a slightly larger one-apse temple (Grewe 2006, 2007, Wengeroth-Weimann 1973).
A very important stage in the palace’s development were the changes made in the Staufen period in the 12th century. At this time the southern part with the surrounding walls was built and the residence took on a defensive character. The second deeper moat around the entire palace was also formed (Grewe 2010). Although the period between the reign of the Staufen dynasty and the 20th century was not included in this study, it is important to present some of the historical facts which took place in Ingelheim at that time. In the 14th century the palace was transferred into the hands of the Order of Augustine by Charles IV. Also, at this time administration of the city of Ingelheim acquired all the authorities of the region of the Electoral Palatinate [ger. Kurpfalz]
(Geißler 2010). During the Thirty Years’ War the buildings of the palatium were substantially damaged and the place fell into ruin, as demonstrated by illustrations and descriptions contained in the doctoral thesis of Daniel Schöpflin (1766) (Fig. 4.2). Its form in the 16th century is presented in Figure 4.1. In the modern period the area of the Saal was intensively extended and in a slightly modified form has not been changed until today.
Fig. 4.2. Engraving showing the condition of the Saalkirche after the Thirty Years’ War (Schöpflin 1766)
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14 Fig. 4.3. Settlements from the Early Middle Ages in Ingelheim (the background – Topographical map 1:25.000 - Topographische Karte 2009)
The map above illustrated the general situation of the settlements in Ingelheim in the 8th century (Fig. 4.3). The church of Saint Remigius with a medieval settlement in Lower Ingelheim [ger. Nieder-Ingelheim], the church of Saint Wigbert with a settlement in Higher Ingelheim [ger. Ober-Ingelheim] and a harbour in Frei-Weinheim (Böhner 1964, 1974, Gierszewska 2009, Schmitz 1974) are presented here.
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15 5. History of the research
Due to the interdisciplinary nature of this work, this chapter presents the history of archaeological research as well as the development of the research method, in this case the generation of Historical Digital Terrain Models.
Due to the large number of terms related to this issue and occurring in the literature, a brief discussion of the problem is also included.
5. 1. Archaeology and architecture
The first regular excavations in Ingelheim began over one hundred years ago (Fig. 5.2, 5.3). These were conducted by the art historian Christian Rauch from 1909 to 1914. Exploring the palace at that time was limited only to the primary area. Although Christian Rauch did not use modern excavation methods, he did expose most of the masonries of the residence. Rauch did not attach too much importance to the stratigraphy and only a few archaeological features, except masonries, were
documented. This resulted in an erroneous interpretation and dating of the various parts of the palace. Rauch included all of the remains of the building into one – the
Carolingian phase (Grewe 1998, 2001, Jacobi et al. 1976).
All that one of the first researchers did not document in the early 20th century during the first archaeological excavations in Ingelheim, Walter Sage tried to do in the 1960s. The reason for starting a re-excavation was the reconstruction of the nave of the church, the so-called Saalkirche. The first archaeological excavation was started at that time. After successful campaigns between 1960 - 1963, the studies were extended to other important areas of the residence. Still, in 1970 the last available space in area of the Saal was digged out and described. The methods that were applied helped in the interpretation and dating of the archaeological features. Also, a stratigraphic sequence was recognised at that time. Many theories introduced by Christian Rauch were not confirmed by these excavations (Grewe 1998, 1999, 2001, 2006, 2007 , Sage 1968, 1976/1977, Wengeroth-Weimann 1973).
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16
Fig. 5.1. Location of the archaeological trenches
in the palatium in Ingelheim between 1909 and 2009
A further review of the previous research was started in 1993. Archaeological excavations have been continued in the whole area of the residence until today. Even in 2010 archaeological investigations were carried out in the southern part of the palace within the framework of the research institution [ger. Forschungsstelle Kaiserpfalz Ingelheim], whose director is Holger Grewe. For almost the last twenty years research has focused primarily on the area of the residence. A settlement, which was an
economic base for the palace, was also examined. The area of the excavation is about 1,785 m², divided into about 50 single trenches (Fig. 5.1).
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17 Fig. 5.2. Archaeological excavations in Ingelheim
between 1909 and 1910
Fig. 5.3. Archaeological excavations in Ingelheim between 1909 and 1910
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18 5. 2. Discussion of terms – DEM/DTM and
study on the Historical Digital Terrain Model
Both the Digital Elevation Model and Digital Terrain Model belong to the raster data model. They contain information about the elevation indicated in the area of a single pixel. The slope of terrain, or exposure could also be calculated from the value of the DTM/DEM.
This term was introduced in the 1950s by U.S. researchers from Massachusetts Institute of Technology (Łyszkowicz 2006). In their opinion “DTM is a statistical representation of continuous physical surface of the Earth by a large number of selected points with known coordinates x, y, in a given coordinate system” (El-Scheimy 1999, after Łyszkowicz 2006, Miller et al. 1958). New definitions of the DTM define this model as a numeric and discrete representation of an elevation of the topographic surface together with the interpolation algorithm, which allows to reconstruct its shape in a certain area (Gaździcki 2001, after Łyszkowicz 2006).
Podobnikar, Stancic and Oštir (2000) agreed with the opinion that the DTM is a digital description of the Earth’s surface and they complemented it with the necessary items, such as:
– slope – exposition – contours
– lines of discontinuity – barriers – superiority
– characteristic points on the ground
Gregory (2003) saw the difference between the DEM and DTM as the type of data that contains a specific model. DEM contains only information about the elevation and has the form of a raster. It could be converted to a DTM.
In archaeological literature, DEM is also called DTM and is defined as a model of the Earth’s surface, but does not necessarily express the topography and landscape forms. According to Wheatley and Gillings (2002) not only terrain could also be shown with the DEM. DTM corresponds only to the elevation of the terrain (model of
topographic height).
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19 In some papers devoted to the issue of these two models, both the DTM and DEM are classified wrongly as 3D models (Gregory 2003), although the current term is 2.5 D (Podobnikar et al. 2000). A full third dimension appears after adding all of the objects which are situated on the ground, such as buildings, a forest, etc., to the model.
Wojciech Widacki described this problem in detail in Wprowadzenie do Systemów Informacji Geograficznej (1997). According to his delineation, the only 2.5D
dimensional object is an area which is used to represent natural, economic, demographic and other entities with a continuous character. It represents not only the land surface, but also precipitation, temperature and density. This surface is characterised by (Widacki 1997, after Goodchild et al. 1992):
– critical points
– culminations and minima – ridges and lower
– passes – faults – fronts – slope – exposures
Three-dimensional objects are volumes with length, width and depth. The depth constitutes the third dimension of the object (Widacki 1997).
The models created in this study can be defined in two ways, according to the literature DEM or DTM. In this thesis the DTM will be used. The models for the medieval phases include the barriers and information about elevation, all critical points, minima, and culminations of the terrain formed by human activity. The interpolation of the model of the contemporary surface was carried out without recognition of
discontinuity lines. Consequently, these continuous surfaces are an expression of the elevation of this area. From all of this models the additionaly information about slope or exposure could be generated. Although medieval utility levels are presented in a
particular part of the residence in the models, this is neither the depth of these objects nor the third dimension. All interpolated DTMs are 2.5 D. surfaces.
Studies on the Historical Digital Terrain Model or Digital Elevation Model are not widely developed. This fact is largely affected by the lack of height data for historical periods. Among the executed studies and used methods, we can distinguish
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20 two ways of obtaining information about historical topography. This is related to the period the particular research refers to. For the 18th and 19th centuries, the terrain could be reconstructed as a Digital Terrain Model by using historical cartographic sources.
Ewa Dąbrowska’s master’s thesis, which describes the differences of terrain in the area of mining exploration in the Zittau Basin, could be an example study related to this topic (Dąbrowska 2008).
Also, some of the archaeological literature is devoted to the creation of a Historical Digital Terrain Model using historical maps. An example might be a model generated for the ancient city of Vienna, in the past called Vindobona. The authors of the publication (Gietl et al. 2004) restored the HDTM of this place based on a topographic map. Unfortunately, the results did not allow the use of the generated model to reconstruct the topography for the 2nd century AD. The next step in this analysis was the gathering of all possible data from archaeological and geological research studies. On the basis of the collected data a new model of the terrain was generated, which corresponds to the situation in the 2nd century AD. This is another way of obtaining some needed information for the generation of a HDTM, especially when there is an absence of cartographic sources. Similarly, other works described the reconstruction of an ancient landscape (Crandell et al. 2008). The authors tried to generate a surface for the 1st and 2nd phase of the Iron Age, in Ma ˘ gura Uroiului in Romania by using archaeological documentation and obtaining data for an ancient settlement. Their analysis was limited only to the area of the excavation, while the surrounding surface was presented with a contemporary model of the terrain.
Hector A. Orengo and Ignacio Fiz, in their publication “The Application of 3D Reconstruction Techniques in the Analysis of Ancient Tarraco’s Urban Topography”
(2008) presented the preliminary results of reconstruction of an ancient landscape.
These studies are devoted to urban topography, but the way of terrain modelling is typical for natural phenomena. They were able to reproduce the coastal areas and the haven of the city of Tarraco on the basis of archaeological data with the TIN method.
The authors did not introduce the line of discontinuity (barriers) to the analysis and they put all the reconstructed buildings onto the terrain model. Katsianis (2004) handled this problem similarly. He reconstruct the stratigraphy and form of the surface for the settlement area of Tell of Knossos on Crete. Also, in this work the discontinuity lines, which limit the different parts of the tell shaped by human activity, were not applied.
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21 Most of the archaeological work focused on the modelling of the ancient surface and is devoted to the documentation of stratigraphy, in other words, of a sequence of particular layers in the cross sections of the archaeological trenches (Cattani et al. 2004;
Putzolu et al. 2004). Often it is not used for further analysis but as the main aim of the research. The question is if the goal of the archaeologists’ work is only to record the finds and features or to reconstruct the past? The study should focus more on the reconstruction of the historical site, e.g. the terrain or ancient surface, but not only make some efforts in advancement of the archaeological documentation.
Brenningmeyer and Begg (2007) presented the process of creating the terrain surface of the ancient city of Tebtunis. This model, however, is a presentation of the archaeological features from the moment of their documentation. They tried to use lines of discontinuity (barriers) to reconstruct the boundaries between the ancient buildings and the particular area of the architectural structure. Also, in this case, the result was not a historical surface of the city terrain.
Another problem often present in the literature is the use of completely flat terrain for a reconstruction of the past. The buildings are placed on this levelled surface (Goriano et al. 2004).
Beex (2004) aptly noted that the creation of Digital Terrain Models is a very complex process and is very important for further analysis. The outcomes of the whole research depend on the form of the generated model, especially if the analysis concerns an ancient surface. However, often a contemporary DEM or DTM will be used. For a small study area the use of the Historical Digital Terrain Model is required. For larger surfaces this is not so important if significant changes of the terrain in the study area were not observed.
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22 6. Data sources
The origin of the data, both related to a particular period of time and to a specific scientific discipline, has a significant influence on its quantity and quality. The following characteristic contains a description of the various data types and sources.
Delineation of the individual sets of data, used for specific interpolation, as well as their technical preparation and processing will be described in Chapter 7. The data sources can be divided into spatial data and non spatial data. The first type of data constitutes a basis for the presented research. The second one helped characterise and distinguish the first set of data. Archaeological and architectural documentation, cadastral maps and field measurements can be included in the sources of these two data sets (Fig. 6.1).
Fig. 6.1. Sources and data (elevation points and barriers) used to generate of the DTM
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23 6.1. Sources of spatial data
The sources of spatial data can be divided into four main groups:
− archaeological documentation
− architectural documentation
− cartographical sources
− terrain measurements
6.1.1. Archaeological documentation
The archaeological documentation that was used to obtain height data and the lines of discontinuity (barriers) consists mainly of drawings of the archaeological sites, i.e. so-called ‘field drawings’, which are made directly during the excavations, and the digital drawings created from the ‘field drawings’. The time of documenting the buildings and the height of the utility level plays a very important role. As previously mentioned, research studies in the palace in Ingelheim which were included in this study were conducted between the years 1909 and 2009. The quality of the drawings, their accuracy and the methods of their preparation are different, both for various excavation campaigns, and for the individual researchers. Some of the results were never published and were included for further processing and evaluation. A large amount of archaeological finds and documentation from the research carried out in the years 1909-1914 was lost during the Second World War.
An important point that should be mentioned is the development of the archaeological methods used to conduct the excavations. The method of stratigraphy was first introduced in the 1960s as the operating method in Ingelheim. It resulted in a changing of the documentation methods. Archaeologists began to point out the type and structure of the unique layers which from this time on were documented in a proper, methodical way. In earlier excavations researchers had focused mainly on the conduct of the masonries, thus destroying other archaeological features (Grewe 1998, 1999, 2001).
Both the elevation data in the form of height points as well as information about the individual lines of discontinuity were obtained from the documentation of the following archaeological excavations:
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24 – archaeological excavation 1909-1914:
These studies were conducted by an art historian, Christan Rauch. The data were obtained mainly from the drawings published in a report of all the excavation campaigns (Jacobi et al. 1976). The results of this research were published incompletely, about 60 years after the excavations. The drawings do not contain information about the archaeological layers that could be attributed to the individual building phases of the residence. Only the remains of floors have been marked on them.
Also, the elevation of the surface area present to the excavation appears in the documentation. Only single points for the interpolation of this surface could be obtained from this documentation. However, it constituted the main source to reconstruct the line of discontinuity (barriers).
Original drawings were made in different scales from 1:20 to 1:100.
– archaeological excavation 1960-1971:
These excavations were conducted under the direction of Walter Sage, Uta Wengeroth- Weimann and Herman Ament. The data include original drawings made during the excavations and digitised versions of AutoCAD. Also, plans from the publication of the research complement this documentation (Wengeroth-Weimann, 1971; Sage 1968, 1976/77). Quite a large number of elevation points were gained from these drawings.
Unfortunately, interpretation was not definite for all points. Complete documentation of these excavations was not included in the preparation of this paper. Some of the drawings were accompanied by a detailed description of the stratigraphy, especially drawings of the cross sections. These descriptions greatly facilitated interpretation of the excavation results. The drawings were made mainly in the scale 1:20. This is the scale of output data. Subsequent digital processing did not influence greater accuracy.
The plans with the results of the excavations were published in the scale 1:50 and 1:100 (Wengeroth-Weimann 1971).
– archaeological excavations 1993-2009:
The largest amount of data were obtained from the documentation of work carried out during the last excavations. From research in the years 1993-2004 only original drawings, made during the excavations and processed in AutoCAD, were used. For research from 2005 the source of information was a complete documentation, which
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25 includes, in addition to the graphical representations of archaeological objects, their description and preliminary interpretation. From these plans a large number of elevation points and lines of discontinuity were acquired, supplemented and verified.
Almost all plans and cross sections were made in the scale 1:20.
The elevation data and the lines of discontinuity from all of the excavations are combined in AutoCAD and then imported into a GIS environment. Further additional information was added in ArcGIS 9.2. Their exact location was determined by connecting all the local coordinate systems into one coherent system – Gauss-Krueger.
The problem of data processing and the systems of coordinates will be described in Chapter 6.2.
6.1.2. Architectural documentation
Architectural documentation is a very small percentage of the overall sources. It includes only the drawings of the cross sections made by documenting the state of the buildings in the area of the Saal in the late 19th/beginning of the 20th century (Zeller 1935). This documentation is a major source of surface interpolation of the 5th building phase in this study. These drawings do not have exact information about the location of the cross sections. These data can be read, however indirectly, by combining them with the individual buildings located in this area today. An additional indication could be the mileage of streets, because only there the elevation points could be measured. Cross sections were made in the scale 1:300 (Fig. 6.2).
Fig. 6.2. Drawing with a cross section of the terrain of the Saal (Zeller 1935)
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26 6.1.3. Cartographic sources
In the thesis the so-called Marksburg plan (17th century) and a cadastral map (2008) were used.
Fig. 6.3. Marksburg plan for the city of Ingelheim from the 17th century (Flath 2005)
The name of the plan Marksburg (Fig. 6.3) comes from the place where it was found, i.e. the archives of the Marksburg castle. It is not known exactly which century this map dates from – probably the 17th century. Presumably the origin of this source could have been connected with the Thirty Years’ War and the possible use of the palatium as a defensive fortress. This is known from other cartographic sources for this area. This plan has great historical value but it is not a typical cadastral plan which could be compared with later examples of cadastral maps. In this plan the area of the Saal was not presented in any cartographic projection. The dimensions of the whole residence and the various elements of urban architecture are not proportionate and consistent with the real constructions, yet they do not deviate from them heavily. Such an element as a scale is not present in the plan. The map is not oriented to the north – but south. The lack of typical modern cartographic legends is also noticeable, although there is a descriptive one. Important buildings are numbered and described by the plan’s
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27 developer. The map does not provide information about the year of origin and references to the author are illegible. The plan was preserved only in the form of low- quality photocopies. Cadastral map was obtained from the Office of Measurement and Cadastre in Bad Kreuznach (ger. Vermessungs- und Katasteramt). The update date of this plan (the year 2002) is quite misleading because in it buildings which were demolished in the early 21st or at the end of the 20th century can be found. This plan was the basis for the location of all archaeological trenches, the related elevation points and the lines of discontinuity (barriers). The author only had a .dxf file of this plan. Due to the size differences of the individual buildings in the plan with the measurements of these objects, it was probably made in the process of digitising an analogue cadastral plan, in a scale of 1:500 or 1:1000. The lack of height information in this source significantly influenced the use of measurements data to interpolate the contemporary DTM.
6.1.4. Terrain measurements
The measurements of the terrain were done with a total station Leica TCR 307.
The first reference points were measured during the excavation campaigns in 2008 and located at the edges of the buildings. They constituted the basis for determining subsequent reference points in the whole area of the Saal. Measurements were made along all streets in the study area. These determine the surfaces of the streets. These data were imported from a text file into a database (Access), and then added to ArcGIS as XY points with a height attribute. An exact description of this process is presented in the next chapter.
6.2. Sources of non spatial data
Among the sources of non spatial data one unique subset was distinguished:
– archaeological documentation
6.2.1. Archaeological documentation
Non spatial data were obtained mainly from the archaeological documentation in the form of reports, descriptions of archaeological features, as well as from some publications (Grewe 1998, 1999, 2001, 2006, 2007, 2010; Grewe et al. 2001; Jacobi et
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28 al. 1976; Sage 1968, 1976/77; Wengeroth/Weimann 1973). These sources played a fundamental role in the interpretation of individual archaeological features, the dating and their relation to the various building phases of the palace. Based on information from the descriptions, particular features correlated directly or indirectly to the utility layer of the residence in different phases were distinguished. Problems of interpretation and its impact on errors of interpolation are further described in the chapter devoted to errors of analysis. This documentation played an important role in the transmission of lines of discontinuity. Not all of the buildings are equally dated and it was necessary to specify the lines of discontinuity for the interpolation of each phase.
All of the sources listed in the chapter about spatial data helped locate both elevation points and lines of discontinuity (barriers). The non spatial data are supplemented as attributes of objects in a geodatabase. The preliminary classification of points and barriers was executed due to each building phase of the residence.
Tab. 6.1. Number of points in the preliminary and representative set obtained for interpolation execution of DTM for the area of the Saal
DTM Number of points in
the preliminary set
Number of points in the representative set
1st phase – 8th century 247 225
2nd phase – 8th / 9th century 338 206 3rd phase – 10th and 11th century 283 204
4th phase – 12th century 273 188
5th phase –19th / 20th century 5 -
6th phase – 21st century 871 866
Sum 1458 (2017) 1689
6.3. Cartographic projection and local reference systems
The selection of cartographical projection was conditioned on the projection of the data sources used for the research. It primarily refers to the cadastral map of Ingelheim, which provided the first selection of all cartographical parameters.
Archaeological sources, such as field drawings, were digitised in AutoCAD and consolidated into a comprehensive plan in the Gauss-Krueger system. These drawings were done in local reference systems. Their measuring grids were composed together as different layers, which helped in joining the various data.
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29 6.3.1. Cartographic projection - Gauss-Krueger
The basic cartographical projection used in Germany is the Gauss-Krueger projection. It is a cylindrical equiangular projection, commonly known as the Mercator projection. It was first applied by Erhard Etzlauba (1462-1532) in the 16th century (1511, 1513), but its construction and structure was published in 1569 by Gerhard Kremer (Mercator). In his particular version points on the globe are mapped on the side surface of the cylinder, which is located laterally to it. This new rule was introduced in 1822 by J. H. Lambert and developed in the 19th century by Carl Friedriech Gauss and Johannes H. L. Krueger. In addition to equiangularity, it maintains a true representation of the length of the main meridian, where the cylinder is tangential to the ellipsoid (Ogorzelska 2006). The farther from the main meridian, the greater the distortion of the map is. The area of the Earth is divided into latitude bands to minimise the
“deformation”. A “rotational ellipsoid surface has been divided into 60 latitude bands, each 6° or 120 bands – 3° each. Every particular band has an individual projection and determines the unique cartesian coordinate system. The widths of the band are selected in a special way to better project on the surface with the least distortion. The area of the central meridian of the latitude band is without any distortion” (Odwzorowanie Gaussa- Krugera, 2005-2010). For Germany 3° latitude bands was designated. The central meridian sets the centre of the cartesian coordinates system for each band. The coordinates are calculated in metres and determine the distance from the central meridian for longitude and from the equator for latitude (Fig. 6.4) (Geoinformatik GmbH 2009).
The palatium in Ingelheim lies at approximately 49.97 degrees latitude and 8.07 degrees longitude. This area can therefore be placed in the band associated with the central meridian 9º, which is the third zone designated for Germany. Due to the geographic location for the entire project, the .prj file Degree Gauss DHDN Zone 3.
from the folder National Grids in ArcGIS 9. 2 was selected (Flacke 2007).
The values for the palatium (aula regia) are:
– 3433475 m – 5538320 m
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30 Fig. 6.4. Map projection – Gauss-Krueger for Germany and the particular zones. (Gauß-Krüger-Koordinatensystem 2010)
6.3.2. Local reference systems
During the archaeological excavations local reference systems are usually used to record the spatial position of the features. This allows for a certain independence of the researchers who are trying to adjust a grid of coordinates for the shape and location of the archaeological trenches. These systems are usually changed in the general map projection, such as, e.g. the Gauss-Krueger. Unfortunately, the creation of many local systems on a single archaeological site carries the risk of introducing errors to each individual grid and to the resulting main system. If the main coordinate axes of the individual system do not run parallel to each other, then their combination into one coherent system can give rise to many problems.
In Ingelheim many local systems of coordinates were used, which was connected with the character of the conducted research. Basically, we are dealing with
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31 three major systems. The first one was introduced by Christian Rauch at the beginning of the 20th century (Jacobi et al. 1976). Its axes are matched to the main axis of the palace, point 0.0 is at the centre of the residence. Points are added in all four directions, which in this case were parallel to the axis of the residence. A similar generalisation of the main world directions was introduced by Uta Wengeroth-Weimann in that she created a local system for the studies carried out between 1960 and 1970 (Wengeroth- Weimann 1973). Point 0.0 was moved to the southern part of the palace. In the present study, conducted since 1993, a number of local coordinate systems was introduced, these were combined together during the digitisation. Due to the fact that a part of the palatium was included in the study area, which was enclosed during the reign of Staufer, the local reference system changed its form. The point 0.0 was placed on the eastern side of the residence and its axis crosses the palatium in its central part. This system is also not parallel to the Gauss-Krueger projection. All local systems of coordinates were combined in the AutoCAD programme. Also, preliminary digitising was executed in this software. It made it possibile to work with all of the systems simultaneously, which was very helpful and functional. The objects were exported from the CAD environment to the ArcGIS with the Gauss-Krueger map projection.
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32 7. Methods
Almost all stages of the presented studies were carried out in the GIS programme – ArcGIS 9.2 (ArcView). This is a programme consisting of several applications, including ArcMap, ArcScene and ArcCatalogue (Ormsby et al. 2004). A small deviation from this was the use of CAD software in the initial phase of operations on the data, as discussed below.
The main operations on the data included:
– data collection – review of the data
– interpolation of the DTM
– analysis of the differences between different historical digital terrain models
All of these processes are described in the following subsections. In addition, some information about technology and software has also been placed there. Verification of the data was extended to the presentation of errors that may appear in the various stages of the research. There is also a described georeference of the historical plan Marksburg, a source of information for the reconstruction of barriers.
7.1. GIS technology and software
For all of the above-mentioned operations on the data a programme from the GIS-environment, the ArcGIS 9.2, was used. Only the initial stage of data collection was executed in AutoCAD 2008, which is often used in computer-aided design and architectural documentation. Also, in archaeology this programme is applied for the digitisation of field drawings. In the case of archaeological research in the palace at Ingelheim, a large part of the documentation has already been digitised in this software (AutoCAD). Access to the digital data helped by in further operations on the drawings in a GIS environment. Unfortunately, it also had a negative impact on the ability to recognise possible errors and it induced difficulty in the interpretation of archaeological features. The issue of errors and archaeological interpretation is widely discussed in Chapter 7.3.
For almost fifty years of the history of GIS a number of different definitions of this environment were framed. Their changes have partly depended on this system’s
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33 development and its recognition by different researchers. One of many definitions indicates that “GIS is a system composed of hardware, software, data, people, proper organisation and rules for collecting, storing, analysing, extending information about areas of the globe” (Dueker et al. 1989, by Litwin et al. 2005). Widacki (1997) defines GIS as the set of operations on data that it can perform. These include the entry, storage and management, processing and extraction of data. In the 1980s GIS was treated only as a programme for data processing (Ozemoy et al. 1981, by Widacki 1997). During the last twenty or thirty years this narrow approach to the Geographical Information System has been extended to the name of a system or environment in which not just hardware or software, but also qualified staff play a significant role (Longley et al. 2006).
In archeology until today GIS has been treated as an experimental tool. It is used mainly to map archaeological features and individual finds. Even though in recent years access to GIS software has greatly increased, there are not many places or universities where archaeologists can learn to use this system (Wheatley et al. 2002). Although the general idea of this system among archaeologists is more similar to that in the 1980s, there is a group of researchers who know and appreciate the great potential of this environment (Wheatley et al. 2002, Conolly et al. 2006). The example of the inappropriate perception of the Geographical Information System is the definition contained in “Wstęp do archeologii” by Dorota Ławecka (2003), that the Geographical Information System “is [...] a combination of computer databases and computer graphics, especially with maps.”
7.2. Data processing and analysis
The elevation data and the lines of discontinuity from all of the excavations were combined in AutoCAD and then imported into a GIS environment. Further additional information was added in ArcGIS 9.2. Their exact location was determined by linking all local coordinate systems into one coherent system – the Gauss-Krueger. The problem of data processing and coordinates systems was desribed in Chapter 6.2.
The collected data used to generate the Historical Digital Terrain Models were subjected to double verification. This was carried out separately for points-data expressing the elevation in each location and the lines of discontinuity (barriers). In this way two data features were created. The data have been linked during the editing of the
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34 database to specific building phases – 1st to 6th. During the next review, namely the determination of a representative set of data (Szkudlarek 2008), a group of the points was reduced by those with significantly different adjacent values. The selection of extreme height values, which was conditioned by anthropogenic influences, is omitted.
The errors caused by a wrong exploration method during the excavation or wrong digitisation could be removed only in some cases. The selection process of the representative data set was carried out also for the line of discontinuity.
7.2.1. Elevation data
All of the points which determine the utility level for each of the building phases of the palatium in Ingelheim were included in the elevation data. They were collected by measuring the height during the archaeological excavations, architectural research and surveying. Depending on the interpretation of the individual layers and archaeological features, the values of the height points and their location may differ from real historical values. Only in the last two phases (5th and 6th) data was obtained from the sources and measurements unequivocal with the present situation. In this case some other measurement errors associated with the location of the points could have occurred.
7.2.1.1. Selection of the preliminary set - standards for selection of the data and their structure
The selection of the preliminary set of data was carried out simultaneously on the sources of all excavations, taking into account the various parts, the so-called zones [ger. Zone] in the area of Saal. The type of sources significantly influenced the form and nature of the preliminary set. The accuracy of the data depended largely on the precision of these sources.
Before the selection and interpretation of specific height values a database with the feature class – points was created. To this class the following attributes were assigned:
– absolute height (AMSL)
– building phase of the residence (1st – 6th) – context (object or archaeological layer)
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35 – zone (K1 – K9)
– excavation (the exact location and name of the excavation)
– author (leader of the excavation / executor of field measurement / others:
Gierszewska / Noszczynski, Grewe, Rauch, Weimann, Zeller)
The elevation points from the excavations carried out between the years 1909- 1914, were obtained mainly from the publication of the results of these studies (Jacobi et al. 1976). Height values were read from figures attached to this study (Fig. 7.1). The remains of the utility level were selected by the author of this thesis, together with the given absolute height. Determination of the location of the points was based on the location of unique excavation and archaeological features. The points which expressed the terrain from the early 20th century were also entered into the database for the 5th phase. Unfortunately, the set of points obtained during Rauch’s research are not numerous, which is caused both by their execution, documentation and lack of a comprehensive evaluation of the results. In this collection only the data for two building phases, namely the 2nd and 5th phase, were selected.
Fig. 7.1. Fragment of the documentation included in the publication Jacobi et al. (1976) with the highlighted utility level
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36 The data collected from the excavations carried out between 1960 and 2009 mainly come from the so-called “field” drawings and their digitised version in AutoCAD 2008.
During the reading of the elevation points from the archaeological documentation and entering them into the database, both the form of a given utility level and the appropriate building phase were interpreted. The interpretation of the individual layers or archaeological features was always unequivocal. Therefore, the following signs “1/2” were entered into the database. Some of the levels were not changed in the next building phases of the palatium and were entered as several phases listed after a comma: “1,2,3” or “2,3,4”. In this case, not only a possibility that the features belong to many phases, but also the lack of data for other phases caused a generalisation of the different levels.
An important element in understanding and determining the exact height was the type of archaeological feature related to the particular utility level. In this study the following objects are distinguished and interpreted:
– the upper limit of the geological layer – the boundary between the geological layers and those of anthropogenic origin. These values were used mainly to create a DTM for the 1st phase
– the upper limit of early medieval occupation layers, connected with a settlement before the foundation of the palace. These values were used mainly to create a DTM for the 1st phase
– a stone setting used to harden the floor for a DTM for the 2nd, 3rd and 4th phase
– a wall coping, in cases where the utility level was also confirmed by other features.
The values were obtained for the 2nd, 3rd and 4th phases (masonries in the apse in the aula regia)
– the present surface of the terrain. These values were obtained from the cross sections of the terrain and assigned to the 6th phase
– the upper limit of a foundation. Values were assigned to the 2nd, 3rd and 4th phase – the lower limit of a burnt layer. Values were assigned to the 2nd, 3rd and 4th phase – stairs. Values were assigned to the 2nd, 3rd, 4th , 5th adn 6th phase
– door sill. Values were assigned to the 2nd, 3rd and 4th phase
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37 – remains of a mortar which determined the level of the building of the residence and its upper limit. Values were assigned to the 2nd, 3rd and 4th phase
– a floor, the concentration of red sandstone and other remains of the floor. Values were assigned to the 2nd, 3rd, 4th and 5th phase
– moat I – lower limit of the moat. Values were assigned to the 1st, 2nd and 3rd phase.
This moat was probably filled in before the expansion of the palace in the 10th century.
Evaluation of this excavation and the dating of ceramics are still in progress.
– moat II – lower limit of the moat. Values were assigned to the 4th phase
– occupation layer – an archaeological layer pointing to the utility level. Values were assigned to the 2nd phase
– screed – layer of mortar poured to harden a floor. Values were assigned to the 2nd, 3rd and 4th phase
The number and quality of the test data are largely dependent on the interpretation and dating of the archaeological features and these were not always unequivocal. In many cases the collected data do not specify a particular utility level but rather its approximate height. For objects such as walls, screed or a wall coping (the walls in the apse in the aula regia), it should be taken into account that the appropriate utility level was probably a few centimetres higher. Even a greater difference in the height between the real level and the collected data could be noticed for the foundation of the masonry or mortar. Due to the cluster character and the small number of data in some areas, these values were entered into the database. All large differences between the values of heights were reviewed in the next phase of selection, namely in the selection of a representative set. Futher data were collected from architectural cross sections and cross sections of the terrain, which contain the values of elevation (Zeller 1935). All values were assigned to the 5th phase. These cross sections were easy to interpret, however, it was difficult to place the cross sections in this area as well as to define the precise height values. In this drawing the buildings which can still be located in the cadastral map were presented. The points were placed on the outside of the buildings along the walls. This was the only single link to the location which could be read from the plans included in Zeller’s publication. After entering the data some inaccuracies were noticed in the height values. Depending on the starting point, after conversion based on a scale, their values were not convergent. In addition, the facades of the buildings shown on the plans could be compared with the present situation. This contributed to the elimination
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38 of these data and an analysis for this phase from the study. The conducted observations helped to formulate the statement that the elevation of the surface in the study area has been changed only minimally since the beginning of the 20th century. After interpolation of the DTM and calculation of the possible differences between the surface of the 20th and 21st centuries, disparities between the rasters could probably derive from a various distribution of the sample points and not from an actual change of the shape or elevation of the terrain.
The last group of the preliminary set of points data was obtained during field measurements made using a total station. These points were assigned to the 6th phase and were used to create a modern Digital Terrain Model.
7.2.1.2. Preparation of the data for particular models – selection of the representative set
As a representative set the elevation values for the specific building phases of the palatium were selected. This selection was carried out in two phases. The first phase was limited to distinction based on the attribute phase – the building phase. Then each group of points in the individual phase was verified by comparing the values of neighbouring points. The elimination of large groups of points was made using the classification and exclusion of selected extreme values.
For the first selection of the representative set the command Select By Attributes from the toolbar Selection was used. Using the query language – SQL – the sets of points belonging to the specific phase were selected. These values, which were assigned by selection of the preliminary set to more as one phase, were added to the collection of the representative set during the next selection. Specific sets assigned by selecting the individual historical periods have been subjected to preliminary verification by comparing the value in the specific groups of points including the line of discontinuity.
The large differences between the neighbouring points, if they were not subjected to human influence, contributed to the removal of the points from each group.
The first stage of verification was performed by using the interpolated surface and the specification of areas with significant differences in the values of pixels. This initial visual – a subjective verification of the surface without the use of barriers did not bring good results (Dąbrowska 2008; Magnuszewski 1999). In some cases only minor
