The world's largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and... more The world's largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and located in Stetten (north of Vienna, Austria) is studied by Harzhauser et al., 2015, 2016; Djuricic et al., 2016. Digital documentation of the unique geological site is provided by terrestrial laser scanning (TLS) at the millimeter scale. Obtaining meaningful results is not merely a matter of data acquisition with a suitable device; it requires proper planning, data management, and postprocessing. Terrestrial laser scanning technology has a high potential for providing precise 3D mapping that serves as the basis for automatic object detection in different scenarios; however, it faces challenges in the presence of large amounts of data and the irregular geometry of an oyster reef. We provide a detailed description of the techniques and strategy used for data collection and processing in Djuricic et al., 2016. The use of laser scanning provided the ability to measure surface points of 46,840 (estimated) shells. They are up to 60-cm-long oyster specimens, and their surfaces are modeled with a high accuracy of 1 mm. In addition to laser scanning measurements, more than 300 photographs were captured, and an orthophoto mosaic was generated with a ground sampling distance (GSD) of 0.5 mm. This high-resolution 3D information and the photographic texture serve as the basis for ongoing and future geological and paleontological analyses. Moreover, they provide unprecedented documentation for conservation issues at a unique natural heritage site.
International journal of earth sciences : Geologische Rundschau, 2018
Shell beds represent a useful source of information on various physical processes that cause the ... more Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to calculate the 3D orientations of a large number of elongate and platy objects (fossilized oyster shells) on a sedimentary bedding plane, developed to support the interpretation of possible depositional patterns, imbrications, or impact of local faults. The study focusses on more than 1900 fossil oyster shells exposed in a densely packed Miocene shell bed. 3D data were acquired by terrestrial laser scanning on an area of 459 m with a resolution of 1 mm. Bivalve shells were manually defined as 3D-point clouds of a digital surface model and stored in an ArcGIS database. An individual shell coordinate system (ISCS) was virtually embedded into each shell and its orientation was determined relative to the coordinate system of the entire, tectonically tilted shell bed. Orientation is described by the rotation angles roll, pitch, and yaw ...
ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016
Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare f... more Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm) and digital surface models (1 mm) are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 <i>Crassostrea gryphoides</i> oysters of various shapes and sizes were computed in the study. Central line calculation included: i) Delaunay triangulation between the foss...
The description and evaluation of geological, sedimentary and paleontological features in the fie... more The description and evaluation of geological, sedimentary and paleontological features in the field is often rather subjective. Many conclusions are based on view measurements on subjectively chosen elements, thought to be representative for the entire setting. One method to overcome this problem is the data acquisition by terrestrial laser scanning, which provides objective data sets. Here we present a key study conducted on the unique fossil oyster reef at Stetten in Lower Austria. The 400-m 2 -large site presents the world's largest fossil oyster biostrome with about 15.000 up to 80-cm-long shells. Despite the excellent preservation and accessibility, the analysis of this spectacular taphocenosis is still missing. No data on orientation, taphonomic grades, distribution and sorting are available. In a first step, a Terrestrial Laserscanner (TLS) was used for the determination of the geometrical 3D structures. The respective area is represented by a "raw" point cloud ...
Laser scanning technology provides a precise and objective methodology for documenting paleontolo... more Laser scanning technology provides a precise and objective methodology for documenting paleontological objects from in-situ localities (to support for instance museum digital documentation). It is a non-destructive approach for documenting in-situ fossils, capturing the geological context and expanding the availability of specimens that may be rare or fragile. This technique was recently applied for a 3D modelling of a protected fossil oyster reef exposed in the geopark "Fossilienwelt Weinviertel" in NE Austria (HARZHAUSER et al., 2015, 2016). The site represents the world's largest fossil oyster reef, but due to the fragility of the fossils it is difficult to study. Figure 1: Terrestrial laser scanning campaign on the world's largest fossil oyster reef in the exhibition hall at Stetten in Austria. The reef's digital surface model provides extensive digital data for developing new algorithm workflows for roughness quantification on individual oyster shell. This allows reliable computations of surface shell condition, i.e. surface roughness used in paleontological analyses of bioerosion, epibenthic overgrowth or abrasion (smoothness of shells). Roughness is derived automatically from geometry data based on the vertical component of surface normals, the sigma0 (standard deviation of plane fitting residuals of reef points) and the local slope (steepness indicator).
Shell beds represent a useful source of information on various physical processes that cause the ... more Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to calculate the 3D orientations of a large number of elongate and platy objects (fossilized oyster shells) on a sedimentary bedding plane, developed to support the interpretation of possible depositional patterns, imbrications, or impact of local faults. The study focusses on more than 1900 fossil oyster shells exposed in a densely packed Miocene shell bed. 3D data were acquired by terrestrial laser scanning on an area of 459 m 2 with a resolution of 1 mm. Bivalve shells were manually defined as 3D-point clouds of a digital surface model and stored in an ArcGIS database. An individual shell coordinate system (ISCS) was virtually embedded into each shell and its orientation was determined relative to the coordinate system of the entire, tectonically tilted shell bed. Orientation is described by the rotation angles roll, pitch, and yaw in a Cartesian coordinate system. This method allows an efficient measurement and analysis of the orientation of thousands of specimens and is a major advantage compared to the traditional 2D approach, which measures only the azi-muth (yaw) angles. The resulting data can variously be utilized for taphonomic analyses and the reconstruction of prevailing hydrodynamic regimes and depositional environments. For the first time, the influence of possible post-sedimentary vertical displacements can be quantified with high accuracy. Here, the effect of nearby fault lines—present in the reef—was tested on strongly tilted oyster shells, but it was found out that the fault lines did not have a statistically significant effect on the large tilt angles. Aside from the high reproducibility, a further advantage of the method is its non-destructive nature, which is especially suitable for geoparks and protected sites such as the studied shell bed.
The world’s largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and loc... more The world’s largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and located in Stetten (north of Vienna, Austria), is studied in this article. Digital documentation of the unique geological site is provided by terrestrial laser scanning (TLS) at the millimeter scale. Obtaining meaningful results is not merely a matter of data acquisition with a suitable device; it requires proper planning, data management, and postprocessing. Terrestrial laser scanning technology has a high potential for providing precise 3D mapping that serves as the basis for automatic object detection in different scenarios; however, it faces challenges in the presence of large amounts of data and the irregular geometry of an oyster reef. We provide a detailed description of the techniques and strategy used for data collection and processing. The use of laser scanning provided the ability to measure surface points of 46,840 (estimated) shells. They are up to 60-cm-long oyster specimens, and their surfaces are modeled with a high accuracy of 1 mm. In addition, we propose an automatic analysis method for identifying and enumerating convex parts of shells. Object surfaces were detected with a completeness of 69% and a correctness of over 75% by means of a fully automated workflow. Accuracy of 98% was achieved in detecting the number of objects. In addition to laser scanning measurements, more than 300 photographs were captured, and an orthophoto mosaic was generated with a ground sampling distance (GSD) of 0.5 mm. This high-resolution 3D information and the photographic texture serve as the basis for ongoing and future geological and paleontological analyses. Moreover, they provide unprecedented documentation for conservation issues at a unique natural heritage site.
Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare f... more Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm) and digital surface models (1 mm) are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 Crassostrea gryphoides oysters of various shapes and sizes were computed in the study. Central line calculation included: i) Delaunay triangulation between the fossil shell boundary points and formation of the Voronoi diagram; ii) extraction of Voronoi vertices and construction of a connected graph tree from them; iii) reduction of the graph to the longest possible central line via Dijkstra's algorithm; iv) extension of longest central line to the shell boundary and smoothing by an adjustment of cubic spline curve; and v) integration of the central line into the corresponding 3D point cloud. The resulting longest path estimate for the 3D central line is a size parameter that can be applied in oyster shell age determination both in paleontological and biological applications. Our investigation evaluates ability and performance of the central line method to measure shell sizes accurately by comparing automatically extracted central lines with manually collected reference data used in paleontological analysis. Our results show that the automatically obtained central line length overestimated the manually collected reference by 1.5% in the test set, which is deemed sufficient for the selected paleontological application, namely shell age determination.
ISPRS Technical Commission V Symposium "Close-range imaging, ranging and applications" ... more ISPRS Technical Commission V Symposium "Close-range imaging, ranging and applications" TIF Travel Grant Report by Ana Djuricic I am taking this opportunity to share my experience and impressions from ISPRS Technical Commission V Symposium. I am a PhD student in Photogrammetry, Department of Geodesy and Geoinformation, Vienna University of Technology where I am involved in the project "Smart-Geology for the World's largest fossil oyster reef" in cooperation with Natural History Museum Vienna (NHM). For me this was the first time to attend the ISPRS Symposium. I was very happy to have been there. It is a great pleasure and honour. I worked very hard in order to prepare my contribution with colleagues from Karlsruhe Institute of Technology (KIT), Germany. When I arrived there the feeling was just "WOW!" The place where symposium was held is such a beautiful place in north part of Italy – Riva del Garda! Pre-Symposium The first day, Sunday morning and a...
The description and evaluation of geological, sedimentary and paleontological features in the fie... more The description and evaluation of geological, sedimentary and paleontological features in the field is often rather subjective. Many conclusions are based on view measurements on subjectively chosen elements, thought to be representative for the entire setting. One method to overcome this problem is the data acquisition by terrestrial laser scanning, which provides objective data sets. Here we present a key study conducted on the unique fossil oyster reef at Stetten in Lower Austria. The 400-m 2 -large site presents the world's largest fossil oyster biostrome with about 15.000 up to 80-cm-long shells. Despite the excellent preservation and accessibility, the analysis of this spectacular taphocenosis is still missing. No data on orientation, taphonomic grades, distribution and sorting are available. In a first step, a Terrestrial Laserscanner (TLS) was used for the determination of the geometrical 3D structures. The respective area is represented by a "raw" point cloud ...
We present the first analysis of population structure and cohort distribution in a fossil oyster ... more We present the first analysis of population structure and cohort distribution in a fossil oyster shell bed based on 1121 shells of the giant oyster Crassostrea gryphoides (von Schlotheim, 1813). Data derive from terrestrial laser scanning of a Lower Miocene shell bed covering 459 m 2. Within two transects, individual shells were manually outlined on a digital surface model and cross-checked based on high-resolution orthophotos, resulting in accurate information on center line length and area of exposed shell surface. A growth model was calculated, revealing this species as the fastest growing and largest Crassostrea known so far. Non-normal distribution of size, area and age data hints at the presence of at least four distinct recruitment cohorts. The rapid decline of frequency amplitudes with age is interpreted to be a function of mortality and shell loss. The calculated shell half-lives range around a few years, indicating that oyster reefs were geologically short-lived structures, which could have been fully degraded on a decadal scale. Crassostrea gryphoides reefs were widespread and common along the Miocene circum-Tethyan coasts. Given its enormous growth performance of ∼ 150 g carbonate per year this species has been an important carbonate producer in es-tuarine settings. Yet, the rapid shell loss impeded the formation of stable structures comparable to coral reefs.
The world's largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and... more The world's largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and located in Stetten (north of Vienna, Austria) is studied by Harzhauser et al., 2015, 2016; Djuricic et al., 2016. Digital documentation of the unique geological site is provided by terrestrial laser scanning (TLS) at the millimeter scale. Obtaining meaningful results is not merely a matter of data acquisition with a suitable device; it requires proper planning, data management, and postprocessing. Terrestrial laser scanning technology has a high potential for providing precise 3D mapping that serves as the basis for automatic object detection in different scenarios; however, it faces challenges in the presence of large amounts of data and the irregular geometry of an oyster reef. We provide a detailed description of the techniques and strategy used for data collection and processing in Djuricic et al., 2016. The use of laser scanning provided the ability to measure surface points of 46,840 (estimated) shells. They are up to 60-cm-long oyster specimens, and their surfaces are modeled with a high accuracy of 1 mm. In addition to laser scanning measurements, more than 300 photographs were captured, and an orthophoto mosaic was generated with a ground sampling distance (GSD) of 0.5 mm. This high-resolution 3D information and the photographic texture serve as the basis for ongoing and future geological and paleontological analyses. Moreover, they provide unprecedented documentation for conservation issues at a unique natural heritage site.
International journal of earth sciences : Geologische Rundschau, 2018
Shell beds represent a useful source of information on various physical processes that cause the ... more Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to calculate the 3D orientations of a large number of elongate and platy objects (fossilized oyster shells) on a sedimentary bedding plane, developed to support the interpretation of possible depositional patterns, imbrications, or impact of local faults. The study focusses on more than 1900 fossil oyster shells exposed in a densely packed Miocene shell bed. 3D data were acquired by terrestrial laser scanning on an area of 459 m with a resolution of 1 mm. Bivalve shells were manually defined as 3D-point clouds of a digital surface model and stored in an ArcGIS database. An individual shell coordinate system (ISCS) was virtually embedded into each shell and its orientation was determined relative to the coordinate system of the entire, tectonically tilted shell bed. Orientation is described by the rotation angles roll, pitch, and yaw ...
ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016
Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare f... more Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm) and digital surface models (1 mm) are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 <i>Crassostrea gryphoides</i> oysters of various shapes and sizes were computed in the study. Central line calculation included: i) Delaunay triangulation between the foss...
The description and evaluation of geological, sedimentary and paleontological features in the fie... more The description and evaluation of geological, sedimentary and paleontological features in the field is often rather subjective. Many conclusions are based on view measurements on subjectively chosen elements, thought to be representative for the entire setting. One method to overcome this problem is the data acquisition by terrestrial laser scanning, which provides objective data sets. Here we present a key study conducted on the unique fossil oyster reef at Stetten in Lower Austria. The 400-m 2 -large site presents the world's largest fossil oyster biostrome with about 15.000 up to 80-cm-long shells. Despite the excellent preservation and accessibility, the analysis of this spectacular taphocenosis is still missing. No data on orientation, taphonomic grades, distribution and sorting are available. In a first step, a Terrestrial Laserscanner (TLS) was used for the determination of the geometrical 3D structures. The respective area is represented by a "raw" point cloud ...
Laser scanning technology provides a precise and objective methodology for documenting paleontolo... more Laser scanning technology provides a precise and objective methodology for documenting paleontological objects from in-situ localities (to support for instance museum digital documentation). It is a non-destructive approach for documenting in-situ fossils, capturing the geological context and expanding the availability of specimens that may be rare or fragile. This technique was recently applied for a 3D modelling of a protected fossil oyster reef exposed in the geopark "Fossilienwelt Weinviertel" in NE Austria (HARZHAUSER et al., 2015, 2016). The site represents the world's largest fossil oyster reef, but due to the fragility of the fossils it is difficult to study. Figure 1: Terrestrial laser scanning campaign on the world's largest fossil oyster reef in the exhibition hall at Stetten in Austria. The reef's digital surface model provides extensive digital data for developing new algorithm workflows for roughness quantification on individual oyster shell. This allows reliable computations of surface shell condition, i.e. surface roughness used in paleontological analyses of bioerosion, epibenthic overgrowth or abrasion (smoothness of shells). Roughness is derived automatically from geometry data based on the vertical component of surface normals, the sigma0 (standard deviation of plane fitting residuals of reef points) and the local slope (steepness indicator).
Shell beds represent a useful source of information on various physical processes that cause the ... more Shell beds represent a useful source of information on various physical processes that cause the depositional condition. We present an automated method to calculate the 3D orientations of a large number of elongate and platy objects (fossilized oyster shells) on a sedimentary bedding plane, developed to support the interpretation of possible depositional patterns, imbrications, or impact of local faults. The study focusses on more than 1900 fossil oyster shells exposed in a densely packed Miocene shell bed. 3D data were acquired by terrestrial laser scanning on an area of 459 m 2 with a resolution of 1 mm. Bivalve shells were manually defined as 3D-point clouds of a digital surface model and stored in an ArcGIS database. An individual shell coordinate system (ISCS) was virtually embedded into each shell and its orientation was determined relative to the coordinate system of the entire, tectonically tilted shell bed. Orientation is described by the rotation angles roll, pitch, and yaw in a Cartesian coordinate system. This method allows an efficient measurement and analysis of the orientation of thousands of specimens and is a major advantage compared to the traditional 2D approach, which measures only the azi-muth (yaw) angles. The resulting data can variously be utilized for taphonomic analyses and the reconstruction of prevailing hydrodynamic regimes and depositional environments. For the first time, the influence of possible post-sedimentary vertical displacements can be quantified with high accuracy. Here, the effect of nearby fault lines—present in the reef—was tested on strongly tilted oyster shells, but it was found out that the fault lines did not have a statistically significant effect on the large tilt angles. Aside from the high reproducibility, a further advantage of the method is its non-destructive nature, which is especially suitable for geoparks and protected sites such as the studied shell bed.
The world’s largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and loc... more The world’s largest fossil oyster reef, formed by the giant oyster Crassostrea gryphoides and located in Stetten (north of Vienna, Austria), is studied in this article. Digital documentation of the unique geological site is provided by terrestrial laser scanning (TLS) at the millimeter scale. Obtaining meaningful results is not merely a matter of data acquisition with a suitable device; it requires proper planning, data management, and postprocessing. Terrestrial laser scanning technology has a high potential for providing precise 3D mapping that serves as the basis for automatic object detection in different scenarios; however, it faces challenges in the presence of large amounts of data and the irregular geometry of an oyster reef. We provide a detailed description of the techniques and strategy used for data collection and processing. The use of laser scanning provided the ability to measure surface points of 46,840 (estimated) shells. They are up to 60-cm-long oyster specimens, and their surfaces are modeled with a high accuracy of 1 mm. In addition, we propose an automatic analysis method for identifying and enumerating convex parts of shells. Object surfaces were detected with a completeness of 69% and a correctness of over 75% by means of a fully automated workflow. Accuracy of 98% was achieved in detecting the number of objects. In addition to laser scanning measurements, more than 300 photographs were captured, and an orthophoto mosaic was generated with a ground sampling distance (GSD) of 0.5 mm. This high-resolution 3D information and the photographic texture serve as the basis for ongoing and future geological and paleontological analyses. Moreover, they provide unprecedented documentation for conservation issues at a unique natural heritage site.
Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare f... more Photogrammetry provides a powerful tool to digitally document protected, inaccessible, and rare fossils. This saves manpower in relation to current documentation practice and makes the fragile specimens more available for paleontological analysis and public education. In this study, high resolution orthophoto (0.5 mm) and digital surface models (1 mm) are used to define fossil boundaries that are then used as an input to automatically extract fossil length information via central lines. In general, central lines are widely used in geosciences as they ease observation, monitoring and evaluation of object dimensions. Here, the 3D central lines are used in a novel paleontological context to study fossilized oyster shells with photogrammetric and LiDAR-obtained 3D point cloud data. 3D central lines of 1121 Crassostrea gryphoides oysters of various shapes and sizes were computed in the study. Central line calculation included: i) Delaunay triangulation between the fossil shell boundary points and formation of the Voronoi diagram; ii) extraction of Voronoi vertices and construction of a connected graph tree from them; iii) reduction of the graph to the longest possible central line via Dijkstra's algorithm; iv) extension of longest central line to the shell boundary and smoothing by an adjustment of cubic spline curve; and v) integration of the central line into the corresponding 3D point cloud. The resulting longest path estimate for the 3D central line is a size parameter that can be applied in oyster shell age determination both in paleontological and biological applications. Our investigation evaluates ability and performance of the central line method to measure shell sizes accurately by comparing automatically extracted central lines with manually collected reference data used in paleontological analysis. Our results show that the automatically obtained central line length overestimated the manually collected reference by 1.5% in the test set, which is deemed sufficient for the selected paleontological application, namely shell age determination.
ISPRS Technical Commission V Symposium "Close-range imaging, ranging and applications" ... more ISPRS Technical Commission V Symposium "Close-range imaging, ranging and applications" TIF Travel Grant Report by Ana Djuricic I am taking this opportunity to share my experience and impressions from ISPRS Technical Commission V Symposium. I am a PhD student in Photogrammetry, Department of Geodesy and Geoinformation, Vienna University of Technology where I am involved in the project "Smart-Geology for the World's largest fossil oyster reef" in cooperation with Natural History Museum Vienna (NHM). For me this was the first time to attend the ISPRS Symposium. I was very happy to have been there. It is a great pleasure and honour. I worked very hard in order to prepare my contribution with colleagues from Karlsruhe Institute of Technology (KIT), Germany. When I arrived there the feeling was just "WOW!" The place where symposium was held is such a beautiful place in north part of Italy – Riva del Garda! Pre-Symposium The first day, Sunday morning and a...
The description and evaluation of geological, sedimentary and paleontological features in the fie... more The description and evaluation of geological, sedimentary and paleontological features in the field is often rather subjective. Many conclusions are based on view measurements on subjectively chosen elements, thought to be representative for the entire setting. One method to overcome this problem is the data acquisition by terrestrial laser scanning, which provides objective data sets. Here we present a key study conducted on the unique fossil oyster reef at Stetten in Lower Austria. The 400-m 2 -large site presents the world's largest fossil oyster biostrome with about 15.000 up to 80-cm-long shells. Despite the excellent preservation and accessibility, the analysis of this spectacular taphocenosis is still missing. No data on orientation, taphonomic grades, distribution and sorting are available. In a first step, a Terrestrial Laserscanner (TLS) was used for the determination of the geometrical 3D structures. The respective area is represented by a "raw" point cloud ...
We present the first analysis of population structure and cohort distribution in a fossil oyster ... more We present the first analysis of population structure and cohort distribution in a fossil oyster shell bed based on 1121 shells of the giant oyster Crassostrea gryphoides (von Schlotheim, 1813). Data derive from terrestrial laser scanning of a Lower Miocene shell bed covering 459 m 2. Within two transects, individual shells were manually outlined on a digital surface model and cross-checked based on high-resolution orthophotos, resulting in accurate information on center line length and area of exposed shell surface. A growth model was calculated, revealing this species as the fastest growing and largest Crassostrea known so far. Non-normal distribution of size, area and age data hints at the presence of at least four distinct recruitment cohorts. The rapid decline of frequency amplitudes with age is interpreted to be a function of mortality and shell loss. The calculated shell half-lives range around a few years, indicating that oyster reefs were geologically short-lived structures, which could have been fully degraded on a decadal scale. Crassostrea gryphoides reefs were widespread and common along the Miocene circum-Tethyan coasts. Given its enormous growth performance of ∼ 150 g carbonate per year this species has been an important carbonate producer in es-tuarine settings. Yet, the rapid shell loss impeded the formation of stable structures comparable to coral reefs.
The protected fossil oyster reef in Stetten, Austria is the world's largest excavated fossil oyst... more The protected fossil oyster reef in Stetten, Austria is the world's largest excavated fossil oyster reef, formed by large sea shells. About 50.000 up to 60-cm-long shells cover a 459 m2 large area. The reef consists primarily of Crassostrea gryphoides shells. In this study, our motivation is to reconstruct the original shell positions with automatic 3D object matching and by finding similar or identical objects in a database with determined shell size (Figure 1). Four initial criteria were defined for the object matching: i) iterative neighborhood search near the examined shell, ii) specified shell convexity: down, up, iii) specified shell side: left, right and iv) shell length with 20% tolerance. For all shells matching the criteria, their centrelines were analyzed in the next step. In analysis, the centreline and its neighboring points are profiled. The profiling produces spatial features, such as sphericity, planarity, scattering and change of curvature. The features describe if the lateral surface of a shell is flat, concave, or convex. All analyzed shells are compared to see if they match together by studying left-sided shells with the right ones. The analysis assumes that shell features should be invariant within a potential pair. Finally, the potential matching candidates are brought close together and pairing is completed using an iterative closest point (ICP) algorithm with a constraint that the matching surface cannot intersect between left and right valve. The proposed method gives a possibility to match and link spatially separated complex objects together if their surface properties have enough feature correspondences along their centreline profiles. The matching over distance supports in making spatial interpretations and objects visualizations in several disciplines, including geology, palaeontology, and biology.
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Papers by Ana Djuricic (Puttonen)
scanning technology has a high potential for providing precise 3D mapping that serves as the basis for automatic object detection in different scenarios; however, it faces challenges in the presence of large amounts of data and the irregular geometry of an oyster reef. We provide a detailed description of the techniques and strategy used for data collection and processing. The use of laser scanning provided the ability to measure surface points of 46,840 (estimated) shells. They are up to 60-cm-long oyster specimens, and their surfaces are modeled with a high accuracy of 1 mm. In addition, we propose an automatic analysis method for identifying and enumerating convex parts of shells. Object surfaces were detected with a completeness of 69% and a correctness
of over 75% by means of a fully automated workflow. Accuracy of 98%
was achieved in detecting the number of objects. In addition to laser scanning measurements, more than 300 photographs were captured, and an orthophoto mosaic was generated with a ground sampling distance (GSD) of 0.5 mm. This high-resolution 3D information and the photographic texture serve as the basis for ongoing and future geological and paleontological analyses. Moreover, they provide unprecedented documentation for conservation issues at a unique
natural heritage site.
scanning technology has a high potential for providing precise 3D mapping that serves as the basis for automatic object detection in different scenarios; however, it faces challenges in the presence of large amounts of data and the irregular geometry of an oyster reef. We provide a detailed description of the techniques and strategy used for data collection and processing. The use of laser scanning provided the ability to measure surface points of 46,840 (estimated) shells. They are up to 60-cm-long oyster specimens, and their surfaces are modeled with a high accuracy of 1 mm. In addition, we propose an automatic analysis method for identifying and enumerating convex parts of shells. Object surfaces were detected with a completeness of 69% and a correctness
of over 75% by means of a fully automated workflow. Accuracy of 98%
was achieved in detecting the number of objects. In addition to laser scanning measurements, more than 300 photographs were captured, and an orthophoto mosaic was generated with a ground sampling distance (GSD) of 0.5 mm. This high-resolution 3D information and the photographic texture serve as the basis for ongoing and future geological and paleontological analyses. Moreover, they provide unprecedented documentation for conservation issues at a unique
natural heritage site.