Terrestrial Laser Scanning Techniques Research Articles

Terrestrial Laser Scanning (TLS) Survey and Building Information Modeling (BIM) of The Edmund Pettus Bridge: A Case Study

Abstract. The comprehensive digital documentation of the Edmund Pettus Bridge, a symbol of the American Civil Rights Movement located in Selma, Alabama, serves as an example of integrating Terrestrial Laser Scanning (TLS) and Building Information Modeling (BIM) technologies for the conservation of heritage infrastructure. This study aimed to employ advanced TLS and other Reality Capture (RC) techniques to generate a high-resolution, three-dimensional representation of the bridge, thereby aiding in its structural assessment and preservation. Utilizing TLS alongside 360-degree photography and UAV surveys, the project achieved detailed coverage of the bridge's architectural and structural features. The data collected was processed into a BIM model using Autodesk Revit, offering comprehensive analysis and preservation planning. The findings from this research highlighted previously undetected areas of material degradation and structural vulnerabilities, emphasizing the value of TLS and BIM in revealing critical insights into the condition of heritage structures. This project preserved the digital memory of an iconic Civil Rights landmark and set a framework for applying digital documentation technologies in heritage infrastructure conservation. The success of this methodology offers a valuable precedent for future conservation efforts, showcasing how RC technologies can enhance the preservation of historical sites and ensure their legacy is maintained for future generations.

Design and Construction Aspects of Concrete Block Paved Vertical Traffic-Calming Devices Located in Home Zone Areas

In recent years, speed reduction measures have been increasingly used, especially in heavily urbanised areas. If local conditions allow, traffic-calming schemes are implemented, which include a variety of traffic-calming measures (TCM). Some of the most common traffic-calming measures are concrete block paved vertical traffic-calming devices (VTCDs), including speed tables, speed humps, speed bumps and raised pedestrian crossings. Different design and construction recommendations apply to the respective VTCD types. The aim of this article is to examine the effectiveness of VTCDs in speed reduction and the impact of horizontal forces on pavement conditions, both within and beyond VTCDs, after over a dozen years of exposure to traffic. For this purpose, speed surveys were carried out on selected two-way streets running through home zones in Poland. The pavements on selected VTCDs were identified and visually assessed for damage, and subsidence areas were estimated using the terrestrial laser scanning (TSL) technique. The analysis resulted in the development of the Deviation Model 3D (DM3D), showing local deviations from the theoretical surface, obtained by superimposing the two models, the Real Surface Digital Terrain Model (RS DTM) and the Theoretical Surface Digital Terrain Model (TS DTM). A comparative analysis of the pavement surface condition and the magnitudes of horizontal forces allowed us to identify the locations of critical spots in VTCDs. The results were used as the basis for developing recommended pavement structures and deriving engineering recommendations for concrete block paving in VTCDs.

Automated flatness assessment for large quantities of full‐scale precast beams using laser scanning

AbstractPrefabrication has been widely used in bridge construction, for which precast beams are produced from a beam yard and constructed with a cast‐in‐suit bridge deck. The developments recently are focusing on large dimensions or large quantities of beam units, which leads to the inevitable challenge of beam quality control. Among them, beam surface flatness as one of the important indicators for manufacturing quality needs to be strictly controlled to ensure structural performance. However, the commonly used methods still rely heavily on manually contact‐based inspection, which is not only time‐consuming but also error‐prone. This paper presents an automated flatness assessment for large quantities of full‐scale precast beams by using terrestrial laser scanning techniques. Through axis calibration, target surface segmentation, and flatness deviation calculation, flatness deviations of the segmented surfaces from the point cloud of the entire beam are calculated, and colored maps are generated to visually assess the flatness quality. The proposed approach was applied to numerical simulated models as well as laboratory‐scale specimens for accuracy validation. Besides, its processing time was also compared to conventional contact‐based inspection during a field test. Moreover, efforts are devoted to applying the proposed method on nearly a thousand precast beams in an in‐field bridge construction project. Results can demonstrate its outperformance not only on accuracy but also the efficiency and practicality when applied to large quantities of full‐scale precast beams.

Aleppo Pixelated: An Urban Reading through Digitized Historical Maps and High-Resolution Orthomosaics Case Study of al-ʿAqaba and al-Jallūm Quarters

This article relies on a combination of digital and analog data to analyze the 2D urban development of al-ʿAqaba and Jallūm districts in the Old City of Aleppo. The dataset consists of vectorized historical maps of the city spanning various historical periods. The oldest map in the collection dates back to the 1900s. Additionally, there are high-resolution orthomosaics created from a 3D model obtained through Terrestrial Laser Scanning (TLS) and Aerial Photogrammetry techniques. Through the analysis and integration of these various data types, the article proposes an analog-digital workflow that tracks the alterations in the urban fabric of the designated study area. The analysis primarily examines the alterations in the city’s two-dimensional layout and the distribution of mass and void. Tracking the changes in the street network of the studied area is the main goal of this research, along with recognizing the spatial changes in the built environment. The article identified changes in both the open spaces and the street layout.

Contribution of Lasergrammetry, Photogrammetry and Electrical Tomography for the Survey and 3D Representation of Caves: Case Study of the Cave of Kef El Baroud, Province of Benslimane, Morocco

The modeling of caves is constantly evolving and the classic modeling tools are giving way to new techniques that are more precise and more practical, indeed scientists are increasingly using 3D modeling to improve the representations of caves, in this study we have used lasergrammetry and photogrammetry which occupy an increasing place in the 3D representation of caves. Their simplicity favors their use for recording and modeling the parietal morphology of caves and the detailed representation of the complexity of Endokarst. As part of the geomorphological study of the Kef El Baroud Cave which is located in the province of Benslimane in Morocco, two modeling methods were carried out, it is a digital survey by lasergrammetry and by photogrammetry of the cave. and its parietal morphologies. The study was completed by a topographical survey with a DistoX rangefinder. The geophysical contribution by electrical tomography was also carried out. The 3D terrestrial laser scanning technique was performed by a LEICA RTC 345 scanner. These measurements made it possible to reconstruct the evolutionary stages of the paragenetic morphologies, and their relationships with the local geomorphology, and the structural elements. The field measurements were integrated into the morphometric analyzes of the digital models, which allowed a large number of observations.The surveys also made it possible to compare the results with those of the photogrammetry carried out by a reflex camera and a wide-angle lens with appropriate editing software.Lasergrammetry and its application have enabled us to precisely position within the point cloud all the details of the covered wall, and thus constitutes, alongside photogrammetry, an interesting means for the geomorphological study of the Caves. An electrical tomography study was coupled with the other measurements and made it possible not only to delimit the walls of the Cave according to the resistivity gradients but also to detect the very probable presence of fractured zones under the Cave which could constitute an aquifer.

Pavement surface distress evaluation using a terrestrial laser scanner

The accurate measurement of pavement distresses is essential for setting preservation and rehabilitation priorities. The manual measurement of surface distresses is the most commonly used method for evaluating the severity of pavement distresses. However, the manual method has low accuracy and consistency. Thus, in the present study, images of different pavement distresses – potholes, cracking, patching and ravelling of selected sections – were captured using a terrestrial laser scanner (TLS). The surface area of these distresses was measured using the Leica Cyclone software. The obtained results were validated by collecting a similar distress pattern at a different location using the same equipment. The measured surface area was executed in a geographic information system platform to develop an automated database for the prioritisation of selected pavement sections of Mumbai City, India for pavement maintenance. It was observed that the TLS technique could be used effectively for safer and more accurate surface distress measurement.

INTEGRATION OF TERRESTRIAL LASER SCANNING AND SMARTPHONE LIDAR: THE CASE STUDY OF LIDZBARK CASTLE

Abstract. In many cases, archaeological research allows to explain the history and evolution of heritage buildings. To support these studies, the availability of reliable 3D representations of such buildings has already been shown to be of remarkable importance. Thanks to the development of Terrestrial Laser Scanning (TLS) and close-range photogrammetric techniques, the generation of such 3D representations by means of remote sensing techniques has become quite common nowadays. While TLS can still be considered as the state-of-the-art method for generating accurate building geometric models, acquisition methods based on the use of mobile devices is becoming a quite attractive solution in order to speed up the survey while also enabling an easier data acquisition on certain narrow places. Despite a plethora of mobile mapping tools is currently available on the market, smartphones are clearly the most widely used smart mobile device in the world, being an ideal solution in terms of usability, portability, and spread. Motivated by this observation and by the recent availability of smartphones provided with Light Detection and Ranging (LiDAR) sensors, this paper aims at investigating the effectiveness of the integration of traditional TLS with smartphone LiDAR on the survey of the castle in Lidzbark Warminski, which dates back to the mid-fourteenth century. TLS, with the scanner set on a standard tripod, was used to scan easily accessible places. TLS mounted on a dedicated tripod, patented by the co-authors of the project was used for less easy-to-reach places. Finally, smartphone LiDAR enabled 3D data acquisition on very hard-to-reach locations, e.g. excavation areas. The model obtained by integrating the data acquired by all the considered methods allowed to properly describe all the area of interest of the castle, being usable for the technical documentation of such historic building. The obtained model significantly advanced the state of knowledge about the castle in Lidzbark Warminski. As a result of the work, many traces of the history of the complex were discovered, proving its gradual evolution.

Advancing Erosion Control Analysis: A Comparative Study of Terrestrial Laser Scanning (TLS) and Robotic Total Station Techniques for Sediment Barrier Retention Measurement

Sediment Barriers (SBs) are crucial for effective erosion control, and understanding their capacities and limitations is essential for environmental protection. This study compares the accuracy and effectiveness of Terrestrial Laser Scanning (TLS) and Robotic Total Station (RTS) techniques for quantifying sediment retention in SBs. To achieve this, erosion tests were conducted in a full-scale testing apparatus with TLS and RTS methods to collect morphological data of sediment retention surfaces before and after each experiment. The acquired datasets were processed and integrated into a Building Information Modeling (BIM) platform to create Digital Elevation Models (DEMs). These were then used to calculate the volume of accumulated sediment upstream of the SB system. The results indicated that TLS and RTS techniques could effectively measure sediment retention in a full-scale testing environment. However, TLS proved to be more accurate, exhibiting a standard deviation of 0.41 ft3 in contrast to 1.94 ft3 for RTS and more efficient, requiring approximately 15% to 50% less time per test than RTS. The main conclusions of this study highlight the benefits of using TLS over RTS for sediment retention measurement and provide valuable insights for improving erosion control strategies and sediment barrier design.

A digital and non-destructive integrated methodology for heritage modelling and deterioration mapping. The case study of the Moorish Castle in Sintra

The development of non-destructive, non-contact and autonomous unmanned techniques is extremely important for the preservation of heritage integrity. This paper presents a digital integrated methodology combining Terrestrial Laser Scanning (TLS), Aerial Digital Photogrammetry (ADP) and Infrared Thermography (IRT), which accelerate data collection and facilitate the creation of point clouds, the deterioration mapping and the state of conservation monitoring of historic structures. Both Digital Photogrammetry and Infrared Thermography were coupled with unmanned aerial vehicle (UAV). The proposed methodology was applied to the Moorish Castle in Sintra, Portugal. Manual Infrared Thermography, complemented with other traditional non-destructive techniques, were also applied in a pilot area for comparison purposes. Resultsdemonstrate the high potential of the integration of TLS, ADP and IRT techniques for heritage modelling digitalization, inspection and deterioration mapping with a positive impact on conservation and restoration projects.

ACCURACY ASSESSMENT TOWARD MERGING OF TERRESTRIAL LASER SCANNER POINT DATA AND UNMANNED AERIAL SYSTEM POINT DATA

Terrestrial Laser Scanning (TLS) techniques are widely preferred for 3D models of small and large objects, buildings, and historical and cultural heritages. However, sometimes relying on a single method for 3D modelling an object/structure is insufficient to arrive at a solution or meet expectations. For example, Unmanned Aerial Systems (UAS) provide perspective for building roofs, while terrestrial laser scanners provide general information about building facades. In this research, several facades of a selected building could not be modelled using terrestrial laser scanning, and UAS was used to complete the missing data for 3D modelling. The transformation matrix, a linear function, is created to merge different data types. In the transformation matrix, the scale was found to be 1:1.012. The accuracy analysis of the produced 3D model was also made by comparing the spatial measurements taken from different building facades and the differences in the measurement values obtained from the 3D model and calculating statistically. According to the accuracy analysis results, the Root Mean Square Error (RMSE) value is approximately 3 cm. The results of the accuracy research, which are within the 95% confidence interval with the three-sigma rule, are approximately 2 cm as RMSE. As a result of the study, it was determined that the data obtained from UAV photogrammetry and the data obtained by the TLS technique could be combined, and the integrated 3D model obtained can be used more efficiently.

Slope gradient impacts on rill morphological characteristics: Using indoor simulation experiment on loamy clay under certain rainfall intensity

In the present study, the rill morphological parameters and their spatial distributions were investigated using indoor rainfall simulation experiments in combination with 3D terrestrial laser scanning technique. Moreover, the optimal rill morphological indicators for rill erosion evaluation were selected based on the relationship of rill morphological parameters and erosion amount. The results showed that total rill length (L), rill density (ρ), maximum width (Wmax), the degree of contour line departure (μ) and shape ratio (η) increased with the increase of slope gradient, whilst the mean rill depth (Dmean), mean rill width (Wmean) and width/depth ratio (W/D) decreased with the increase of slope gradient. The spatial distribution pattern of each rill morphology parameter was also changed with slope gradient, showing differences in upper slope, central slope and lower slope. Most of rill morphological parameters were highly correlated with rill erosion amount, except the mean rill width (Wmean), degree of contour line departure (μ), and rill density (ρ). The plane area of rill (Parea) or the degree of rill dissection (δ) was selected as the optimal morphological parameter to predict rill erosion amount, followed by the maximum area of cross section (CSmax), the maximum rill depth (Dmax), and the mean rill depth (Dmean). In particular, the parameters of CSmax and Dmax are recommended for rill erosion estimation based on the convenience and ease of data acquisition.

Laser-scan based pose monitoring for guiding erection of precast concrete bridge piers

Precast construction creates cost-effective structures by rapidly assembling prefabricated components. The emerging trend in increasing weights and scales of precast members, poses new challenges on installation quality. This study proposes an efficient and accurate pose measurement technique for guiding the erection of precast bridge piers using terrestrial laser scanning techniques. An arbitrary position of the scanner is allowed which is pre-calibrated by a single scan before the erection. For data analysis, a novel coarse-to-fine registration method is proposed to automatically align the scan model with the design model. A feature descriptor based on two-dimensional local kernel density map is used for fast coarse registration. An objected-oriented iterative closest point (ICP) registration based on virtual scan generator and nearest neighbour search is adopted for accurate fine registration. The proposed system was evaluated in the construction of an expressway viaduct and shows the potential for improving the installation efficiency and accuracy.

A Field Investigation on Gully Erosion and Implications for Changes in Sediment Delivery Processes in Some Tributaries of the Upper Yellow River in China

Erosion and sediment delivery have been undergoing considerable variations in many catchments worldwide owing to climate change and human interference. Monitoring on-site erosion and sediment deposition is crucial for understanding the processes and mechanisms of changes in sediment yield from the catchments. The Ten Kongduis (kongdui is the transliteration of ephemeral creeks in Mongolian) are 10 tributaries of the upper Yellow River. Severe erosion in the upstream hills and gullies and huge aeolian sand input in the middle reaches had made the 10 tributaries one of the main sediment sources of the Yellow River, but the gauged sediment discharge of the tributaries has decreased obviously in recent years. In order to find out the mechanisms of changes in the sediment load of the tributaries, topographic surveys of four typical gullies in 3 of the 10 tributaries were made repeatedly in the field with the terrestrial laser scanning (TLS) technique. The results show that all the monitored gullies were silted with a mean net rate of 587–800 g/m2 from November 2014 to June 2015 and eroded by a mean net rate of 185–24,800 g/m2 from June to November 2015. The monitoring data suggest that the mechanism of interseasonal and interannual sediment storage and release existed in the processes of sediment delivery in the kongduis. The contrast of the low gauged sediment load of the kongduis in recent years against the high surveyed gully erosion indicates the reduction in their sediment delivery efficiency, which can be attributed to the diminution in hyperconcentrated flows caused mainly by the increase in vegetation coverage on slopes and partly by construction of sediment-trapping dams in gullies.

Boulder displacements along rocky coasts: A new deterministic and theoretical approach to improve incipient motion formulas

Several impacts of high-energy marine events – tsunamis and storms – which have occurred along the Mediterranean coasts, have determined boulder displacements in different ways, spanning from sliding and overturning to saltation. The dynamics of these transport modes to the incipient motion of boulders, strictly connected to the pre-setting scenarios, has been extensively studied considering the boulder size and the hydrodynamic parameters of high-energy marine events, such as the wave flow velocity. Notwithstanding this, known hydrodynamic relationships provide some unrealistic flow values concerning the real wave flow velocity registered along the Mediterranean coasts. In this work, a new deterministic and theoretical approach has been developed to assess the minimum flow velocities required to move coastal boulders. The proposed approach is based on the introduction of modified parameters, which consider the real dimensional features of the boulders assessed by means of modern geophysical survey techniques, into the incipient motion formulas. To accurately define these parameters, we created a database composed of boulders located along the coasts of Apulia and Sicily (Italy) that were surveyed in previous studies through photogrammetric and Terrestrial Laser Scanner techniques. Results highlighted that the incipient motion formulas, revised with the new proposed parameters, provided minimum flow velocity values for boulder transport initiation, which were significantly lower compared to those calculated using the previous approach. Thus, the proposed modifications are a step forward towards defining the dynamics of boulder displacement.

A deep learning-based indoor acceptance system for assessment on flatness and verticality quality of concrete surfaces

Flatness and verticality quality assessment (FVQA) must be strictly controlled during the indoor acceptance testing. Existing FVQA methods using terrestrial laser scanning (TLS) rely on the as-designed model to assist in locating inspected objects, while sophisticated deep learning techniques excel in the object recognition. Therefore, based on the TLS and deep learning technique, this study presents a general indoor acceptance system including the indoor semantic segmentation, component surface segmentation, and FVQA. In particular, a dataset consisting of 145 sets of room point cloud data (PCD) is created to train the adopted point-based neural network. An image processing-based method is proposed to check the flatness and verticality of identified concrete surfaces. Experiments are conducted on two completed residences to verify the practicality and convenience of the proposed indoor acceptance system by comparing the calculated flatness and verticality with the field measurements. The experimental results show that the deep learning technique used in this study has a good recognition accuracy (over 85%) for large concrete surfaces in residential PCD, and the proposed indoor acceptance system provides more rigorous inspection results compared with the manual inspection method.

Accuracy Assessment of Cultural Heritage Models Extracting 3D Point Cloud Geometric Features with RPAS SfM-MVS and TLS Techniques

A proper classification of 3D point clouds allows fully exploiting data potentiality in assessing and preserving cultural heritage. Point cloud classification workflow is commonly based on the selection and extraction of respective geometric features. Although several research activities have investigated the impact of geometric features on classification outcomes accuracy, only a few works focused on their accuracy and reliability. This paper investigates the accuracy of 3D point cloud geometric features through a statistical analysis based on their corresponding eigenvalues and covariance with the aim of exploiting their effectiveness for cultural heritage classification. The proposed approach was separately applied on two high-quality 3D point clouds of the All Saints’ Monastery of Cuti (Bari, Southern Italy), generated using two competing survey techniques: Remotely Piloted Aircraft System (RPAS) Structure from Motion (SfM) and Multi View Stereo (MVS) techniques and Terrestrial Laser Scanner (TLS). Point cloud compatibility was guaranteed through re-alignment and co-registration of data. The geometric features accuracy obtained by adopting the RPAS digital photogrammetric and TLS models was consequently analyzed and presented. Lastly, a discussion on convergences and divergences of these results is also provided.

Application of Territorial Laser Scanning in 3D Modeling of Traditional Village: A Case Study of Fenghuang Village in China

Historical villages bear historical, cultural, architectural, aesthetic, and landscape values, but they are facing a series of dangers and problems during the process of urbanization. Digital survey for traditional villages plays a crucial role in the preservation, planning, and development of this kind of heritage. The introduction of the terrestrial laser scanning technique is essential for heritage surveying, mapping, and modeling due to its advantages of noncontact measurement, accurate sensing of complex objects, and efficient operation. In recent years, TLS and related processing software (“SCENE”) have been widely presented as effective techniques for dealing with the management and protection of historical buildings in Fenghuang village. Thus, this paper highlights the process of using laser scanning to obtain architectural data, process point clouds, and compare the characteristics of historical buildings in Fenghuang village. The cloud-to-cloud registration technique is applied to build point clouds. As a result of model construction, some architectural patterns are summarized in this village, such as the spatial sequence of ancestral halls, the dominant position of memorial halls, and the character of building decorations and roof slopes. Furthermore, a BIM model is also explained to fulfill the statistical function for architectural components. In the future, more research can be fulfilled based on the built point cloud model, which will be beneficial for the development of the whole village.

Reliability and effectiveness of laser scanners in future construction efforts on the Moon and Mars

The exploration and conquest of the Moon and Mars is very likely in the near future. Therefore the erection of lunar and Martian structures, suitable for permanent human presence is increasingly discussed by the scientific community. Various concepts have been proposed for creation of lunar and Martian permanent bases. Techniques ranging from 3D printing of concrete, through utilization of natural caves to inflatable pressurized tensile structures are considered. In authors' opinion a fast, accurate and remote measuring technique will be necessary for successful completion of majority of extra-terrestrial construction tasks. The terrestrial laser scanning technique should be used for the lunar and Martian construction projects. To assess the suitability of terrestrial laser scanning techniques which are going to be used on the Moon and Mars, initial measurements should be conducted on Earth. Unfortunately extra-terrestrial soils are not available for general research. The only feasible solution is to use lunar and Martian soil simulants to practice construction technologies, techniques and strategies. The main aim of this research programme is radiometric and geometric analysis of TLS point clouds collected during the measurement of lunar and Martian soil simulants targets. The conducted research programme was focused on the analysis of a laser beam dispersion and absorption in soil simulants. It should be noted that the dispersion and absorption of a laser beam for the scanned surface is a key factor in TLS remote measurements. The advantages and limitations of TLS technique for possible lunar and Martian applications was discussed. Areas of subsequent research were pointed out. In the first section the brief state-of-the-art was given in context of the conducted research programme. Subsequently, in section two used specimens and equipment was described. The third section of the paper was dedicated to present the conducted research programme. The achieved results were shown in section four in the form of tables and graphs. Finally, in section five the discussion was carried out and followed by a list of drawn conclusions. It was proved that TLS technique can be used to effectively scan LSS and MSS, thus scanning on the Moon and Mars is enabled.

Evaluation of Tunnel Contour Quality Index on the Basis of Terrestrial Laser Scanning Data

Abstract The Tunnel Contour Quality Index (TCI) is an index established by Kim and Bruland for an effective management of a tunnel contour quality. It is estimated on a basis of measurements of two contour profiles within a single blasting round, using a laser profiler. However, the representativeness of measurement results obtained that way for the assessment of a contour quality of the entire blasting round is disputable. Terrestrial laser scanning (TLS) technology, combined with available numerical surface modeling tools, enables development of three-dimensional models of a monitored surface. The article reports results of TCI calculations based on TLS data. The presented TLS technique is based not only on selected cross-sections of the tunnel contour but also on the description of the morphology of the tunnel contour surface. The case study concerns measurements of the “Mały Luboń” tunnel niche, located in Naprawa, Poland. The TCI values for three blasting rounds were determined in accordance with Kim and Bruland's guidelines and were compared to TCI values determined with the proposed TLS technique. On a basis of this comparison, it can be concluded that the results obtained with the TLS technique are more reliable and representative for description of the contour quality of the entire blasting round than results obtained with the laser profiling technique.

Variations in Hard‐Bedded Topography Beneath Glaciers

AbstractThe morphology of glacier beds is a first‐order control on their slip speeds and consequent rates of subglacial erosion. As such, constraining the range of bed shapes expected beneath glaciers will improve estimates of glacier slip speeds. To estimate the variability of subglacial bed morphology, we construct 10 high‐resolution (10 cm) digital elevation models of proglacial areas near current glacier margins from point clouds produced through a combination of terrestrial laser scanning and photogrammetry techniques. The proglacial areas are located in the Swiss Alps and the Canadian Rockies and consist of predominantly debris‐free bedrock of variable lithology (igneous, sedimentary, and metamorphic). We measure eight different spatial parameters intended to describe bed morphologies generated beneath glaciers. Using probability density functions, Bhattacharyya coefficients, principal component analysis, and Bayesian statistical models we investigate the significance of these spatial parameters. We find that the parameters span similar ranges, but the means and standard deviations of the parameter probability density functions are commonly distinct. These results indicate that glacier flow over bedrock may lead to a convergence toward a common bed morphology. However, distinct properties associated with each location prevent morphologies from being uniform.