Showing papers on "Photogrammetry published in 2008"

Topographic laser ranging and scanning : principles and processing

Abstract: Introduction to Laser Ranging, Profiling, and Scanning, G Petrie and C K Toth Airborne and Spaceborne Laser Profilers and Scanners, G Petrie and C K Toth Terrestrial Laser Scanners, G Petrie and C K Toth LiDAR Systems and Calibration, A Wehr Pulsed Laser Altimeter Ranging Techniques and Implications for Terrain Mapping, D Harding Georeferencing Component of LiDAR Systems, N El-Sheimy Waveform Analysis for Small-Footprint Pulsed Laser Systems, U Stilla and B Jutzi Strip Adjustment and Registration, C K Toth Accuracy, Quality Assurance, and Quality Control of LiDAR Data, A Habib Management of LIDAR Data, L Graham LiDAR Data Filtering and DTM Generation, N Pfeifer Forest Inventory Using Small-Footprint Airborne Lidar, J Hyyppa, H Hyyppa, X Yu, H Kaartinen, A Kukko, and M Holopainen Integration of LiDAR and Photogrammetric Data: Triangulation and Ortho Rectification, A Habib Feature Extraction from Lidar Data in Urban Areas, F Bretar Building Extraction from LiDAR Point Clouds Based on Clustering Techniques, J Shan and A Sampath Building and Road Extraction by LiDAR and Imagery, F Rottensteiner and S Clode A Data-Driven Method for Modeling 3D Building Objects Using a Binary Space Partitioning Tree, G Sohn, X Huang, and V Tao A Framework for Automated Construction of Building Models from Airborne LIDAR Measurements, K Zhang Quality of Buildings Extracted from Airborne Laser Scanning Data: Results of an Empirical Investigation on 3D Building Reconstruction, E Gulch, H Kaartinen, and J Hyyppa Index

A Comprehensive Automated 3D Approach for Building Extraction, Reconstruction, and Regularization from Airborne Laser Scanning Point Clouds

Abstract: Three dimensional city models are necessary for supporting numerous management applications. For the determination of city models for visualization purposes, several standardized workflows do exist. They are either based on photogrammetry or on LiDAR or on a combination of both data acquisition techniques. However, the automated determination of reliable and highly accurate city models is still a challenging task, requiring a workflow comprising several processing steps. The most relevant are building detection, building outline generation, building modeling, and finally, building quality analysis. Commercial software tools for building modeling require, generally, a high degree of human interaction and most automated approaches described in literature stress the steps of such a workflow individually. In this article, we propose a comprehensive approach for automated determination of 3D city models from airborne acquired point cloud data. It is based on the assumption that individual buildings can be modeled properly by a composition of a set of planar faces. Hence, it is based on a reliable 3D segmentation algorithm, detecting planar faces in a point cloud. This segmentation is of crucial importance for the outline detection and for the modeling approach. We describe the theoretical background, the segmentation algorithm, the outline detection, and the modeling approach, and we present and discuss several actual projects.

Validity and reliability of craniofacial anthropometric measurement of 3D digital photogrammetric images.

Abstract: Background: Direct anthropometry performed during a patient examination is the standard technique for quantifying craniofacial dysmorphology, as well as for surgical planning and outcome assessment. Several new technologies have been designed to computerize anthropometric measurements, including three-dimensional (3D) digital photogrammetry. These digital systems have the advantage of acquiring patient craniofacial surface images quickly and noninvasively. Before morphometry using digital photogrammetry can be applied in clinical and research practice, it must be assessed against direct anthropometry. Objective: To evaluate the validity and reliability of facial anthropometric linear distances imaged by 3D digital photogrammetry with respect to direct anthropometry. Design, Setting, Participants, Measures: Standard craniofacial distances were directly measured twice on 20 normal adult volunteers. Craniofacial surfaces were also imaged using the 3dMDface digital photogrammetry system, and distance...

Deformation measurement using terrestrial laser scanning data and least squares 3D surface matching

Abstract: The use of Terrestrial Laser Scanning (TLS) data for deformation measurement is gaining increasing interest. This paper is focused on a new procedure for land deformation monitoring based on repeated TLS scans. The kernel of the procedure is the least squares 3D surface matching proposed by Gruen and Akca [Gruen, A., Akca, D., 2005. Least squares 3D surface and curve matching. ISPRS Journal of Photogrammetry and Remote Sensing 59 (3), 151−174]. This paper describes the three main steps of the procedure, namely the acquisition of the TLS data, the global co-registration of the point clouds, and the estimation of the deformation parameters using local surface matchings. The paper briefly outlines the key advantages of the proposed approach, such as the capability to exploit the available high data redundancy using advanced analysis tools, the flexibility of the proposed solution, and the capability of providing fully 3D deformation measurements, including displacement vectors and rotations. Furthermore, it illustrates the performance of the proposed procedure with a validation experiment where a deformation measurement scenario was simulated and TLS and topographic data were acquired. From the analysis of this experiment, interesting features are highlighted: the validation errors below 1 cm in the displacements and below 1 gon in the rotations of small targets measured at a distance of 134 m; the increase by factor two of the errors when the same scene is measured from a distance of 225 m; and the importance of an accurate global co-registration in order to avoid systematic errors in the estimated deformation parameters. It is interesting to note that the above results were achieved under non-optimal conditions, e.g. using non-calibrated data and sub-optimal targets from the matching viewpoint. Besides the simulation experiment, the validation results achieved on landslide test site are briefly discussed.

Remote Sensing and GIS

Abstract: PART 1: REMOTE SENSING AND IMAGE ANALYSIS 1. Concept of Remote Sensing 2. Remote Sensing Platform and Sensor Characteristics 3. History of Remote Sensing and Indian Space Program 4. Photographic Imaging 5. Digital Imaging 6. Microwave Remote Sensing 7. Ground Truth Data and GPS 8. Photogrammetry 9. Visual Image Interpretation 10. Digital Image Processing 11. Data integration, analysis and presentation 12. Applications of Remote Sensing PART 2: GEOGRAPHIC INFORMATION SYSTEMS AND GEOSPATIAL ANALYSIS 13. Concept of GIS 14. Functions and Advantages of GIS 15. Spatial Data Model 16. Attribute Data Management and Metadata Concept 17. Process of GIS 18. Geospatial Analysis 19. Planning, Implementation and Management of GIS 20. Modern Trend of GIS APPENDICES

Comparison methods of terrestrial laser scanning, photogrammetry and tacheometry data for recording of cultural heritage buildings

Abstract: Cultural heritage documentation projects very often combine different acquisition methods as tacheometry, photogrammetry and terrestrial laser scanning. In this paper we compare these three methods for recording of heritage buildings. Our test object is the medieval castle of Haut-Andlau (Alsace, France), documented in 2006-2008. This castle is of particular interest for our investigations since its architecture is the result of different construction styles completed over the centuries. Old buildings are rarely regularly shaped and most of their facades are made of very complex curved structures. The documentation of the castle became a true challenge, regarding the constraints implied on the one hand by the steep and abrupt terrain surrounding the castle and on the other hand by the dense and broadening vegetation close to the castle. It became rapidly obvious that a unique technique would not overcome the vegetation and relief obstacles. The main part of the data capture was based on TLS. For completion of the laser scanner data at occluded building parts and for accuracy assessment, stereoscopic as well as multi-image models have been captured. Advantages and disadvantages of the different methods will be discussed in this paper. A quality assessment leads to the analysis of the models derived from each technique and to a crucial experience for further campaigns.

Using close range terrestrial digital photogrammetry for 3-D rock slope modeling and discontinuity mapping in the United States

Abstract: Close range terrestrial digital photogrammetry has evolved into a useful remote characterization tool for rock slope practitioners, particularly in situations where manual discontinuity measurement may be impractical or dangerous. The primary products are high-resolution 3-D photographic surface models that have several advantages over terrestrial laser scanner point clouds, including cost, equipment portability and the ability to include discontinuities that appear as linear traces rather than flat planar surfaces. Models can be made with currently available off-the-shelf digital cameras while commercially available software provides virtual mapping capabilities that allow practitioners to identify, map, and quickly calculate the orientation of modeled discontinuities using the same experience-based logical process used by traditional fieldworkers. Comparison of manually measured and model-derived discontinuity orientations shows good agreement both between individual discontinuities and entire sets of discontinuities. Application of the technique is illustrated using five recent mining and civil engineering projects in the United States.

Mapping canopy height using a combination of digital stereo-photogrammetry and lidar

Abstract: Ranging techniques such as lidar (LIght Detection And Ranging) and digital stereo-photogrammetry show great promise for mapping forest canopy height. In this study, we combine these techniques to create hybrid photo-lidar canopy height models (CHMs). First, photogrammetric digital surface models (DSMs) created using automated stereo-matching were registered to corresponding lidar digital terrain models (DTMs). Photo-lidar CHMs were then produced by subtracting the lidar DTM from the photogrammetric DSM. This approach opens up the possibility of retrospective mapping of forest structure using archived aerial photographs. The main objective of the study was to evaluate the accuracy of photo-lidar CHMs by comparing them to reference lidar CHMs. The assessment revealed that stereo-matching parameters and left-right image dissimilarities caused by sunlight and viewing geometry have a significant influence on the quality of the photo DSMs. Our study showed that photo-lidar CHMs are well correlated to their lidar counterparts on a pixel-wise basis (r up to 0.89 in the best stereo-matching conditions), but have a lower resolution and accuracy. It also demonstrated that plot metrics extracted from the lidar and photo-lidar CHMs, such as height at the 95th percentile of 20 m×20 m windows, are highly correlated (r up to 0.95 in general matching conditions).

Very-high-resolution mapping of river-immersed topography by remote sensing:

Abstract: A bstract: Remote sensing has been used to map river bathymetry for several decades. Non-contact methods are necessary in several cases: inaccessible rivers, large-scale depth mapping, very shallow rivers. The remote sensing techniques used for river bathymetry are reviewed. Frequently, these techniques have been developed for marine environment and have then been transposed to riverine environments. These techniques can be divided into two types: active remote sensing, such as ground penetrating radar and bathymetric lidar; or passive remote sensing, such as through-water photogrammetry and radiometric models. This last technique ± which consists of fi nding a logarithmic relationship between river depth and image values ± appears to be the most used. Fewer references exist for the other techniques, but lidar is an emerging technique. For each depth measurement method, we detail the physical principles and then a review of the results obtained in the fi eld. This review shows a lack of data for very shallow rivers, where a very high spatial resolution is needed. Moreover, the cost related to aerial image acquisition is often huge. Hence we propose an application of two techniques, radiometric models and through-water photogrammetry, with very high-resolution passive optical imagery, light platforms, and off-the-shelf cameras. We show that, in the case of the radiometric models, measurement is possible with a spatial fi ltering of about 1 m and a homogeneous river bottom. In contrast, with through-water photogrammetry, fi ne ground resolution and bottom textures are necessary.

Accuracy assessment of lidar‐derived digital elevation models

Abstract: Despite the relatively high cost of airborne lidar-derived digital elevation models (DEMs), such products are usually presented without a satisfactory associated estimate of accuracy. For the most part, DEM accuracy estimates are typically provided by comparing lidar heights against a finite sample of check point coordinates from an independent source of higher accuracy, supposing a normal distribution of the derived height differences or errors. This paper proposes a new methodology to assess the vertical accuracy of lidar DEMs using confidence intervals constructed from a finite sample of errors computed at check points. A non-parametric approach has been tested where no particular error distribution is assumed, making the proposed methodology especially applicable to non-normal error distributions of the type usually found in DEMs derived from lidar. The performance of the proposed model was experimentally validated using Monte Carlo simulation on 18 vertical error data-sets. Fifteen of these data-sets were computed from original lidar data provided by the International Society for Photogrammetry and Remote Sensing Working Group III/3, using their respective filtered reference data as ground truth. The three remaining data-sets were provided by the Natural Environment Research Council’s Airborne Research and Survey Facility lidar system, together with check points acquired using high precision kinematic GPS. The results proved promising, the proposed models reproducing the statistical behaviour of vertical errors of lidar using a favourable number of check points, even in the cases of data-sets with non-normally distributed residuals. This research can therefore be considered as a potentially important step towards improving the quality control of lidar-derived DEMs.

Fusion of Lidar and Imagery for Reliable Building Extraction

Abstract: We propose a new building detection and description algorithm for lidar data and photogrammetric imagery using directional histograms, splitting and merging segments, and line segments matching. Our algorithm consists of three steps. In the first step, we extract initial building regions from lidar data. Here, we apply a modified local maxima technique coupled with directional histograms and the entropies of these histograms. In the second step, given the color segmentation results from the photogrammetric imagery, we extract coarse building boundaries based on the lidar results with region segmentation and merging from aerial imagery. In the third step, we extract precise building boundaries based on the coarse building boundaries using line segments matching and perceptual grouping. Experimental results on multisensor data demonstrate that the proposed algorithm produces accurate and reliable results.

High-resolution LiDAR and photogrammetric survey of the Fumanya dinosaur tracksites (Catalonia): implications for the conservation and interpretation of geological heritage sites

Abstract: Increasing political and social awareness of the importance of protecting the geological heritage is compelling geoscientists to consider new methods for reconciling conservation and exploration of their research sites. Terrestrial Light Detection And Range (LiDAR) imaging is an accurate method of collecting 3D spatial data that has so far been under-utilized in the geological sciences. This aim of this paper is to assess the value of integrated LiDAR and photogrammetric imaging as a tool for synchronizing scientific exploration with conservation of geological heritage sites. Fumanya (Catalonia) is one of the most important Cretaceous tracksites in Europe, but the nature of exposure of the track-bearing surface has hindered quantitative documentation of the ichnites. Using integrated Light Detection And Range (LiDAR) imaging and photogrammetry it has been possible to construct high-resolution Digital Outcrop Models (DOM) of the tracksites. Photo-textured DOMs are a powerful visualization tool and function as fully 3D interactive databases that preserve information about the site that would otherwise be lost to erosion. LiDAR-derived DOMs have the potential to contribute profoundly to future geoconservation projects, particularly as a tool for documenting and monitoring heritage sites and promoting education and tourism. LiDAR scanning also provides sufficient resolution to perform robust quantitative analysis of dinosaur tracks.

Digital photogrammetric method and apparatus using intergrated modeling of different types of sensors

Abstract: Disclosed is a digital photogrammetric method and apparatus using the integrated modeling of different types of sensors. A unified triangulation method is provided for an overlapping area between an aerial image and a satellite image that are captured by a frame camera and a line camera equipped with different types of sensors. Ground control lines or ground control surfaces are used as ground control features used for the triangulation. A few ground control points may be used together with the ground control surface in order to further improve the three-dimensional position. The ground control line and the ground control surface may be extracted from LiDAR data. In addition, triangulation may be performed by bundle adjustment in the units of blocks each having several aerial images and satellite images. When an orthophoto is needed, it is possible to generate the orthophoto by appropriately using elevation models with various accuracies that are created by a LiDAR system, according to desired accuracy.

Photogrammetric image acquisition and image analysis of oblique imagery

Abstract: Because of the intuitive human perception of the oblique view, photogrammetrists’ attention has recently returned to oblique images. The demand for oblique imagery has been notably pushed by digital representations of the globe such as Microsoft’s Virtual Earth and by the development of special GIS viewers including those by Pictometry and MultiVision. In this contribution the broad spectrum of applications of oblique images is presented. Most commonly oblique images are acquired with flexible digital airborne camera systems, which allow for easy collection of such imagery with photogrammetric quality. The digital airborne remote sensing system PFIFF developed at Rostock University will be introduced briefly. However, flight planning for oblique imagery differs from that for vertical aerial surveys. Two test flights with mono and stereo oblique images are presented. The data processing, display and measurement within oblique images from different perspectives requires new software such as MultiVision. Oblique images may also be used to texture 3D city models.

A framework of region-based spatial relations for non-overlapping features and its application in object based image analysis

Abstract: Object based image analysis (OBIA) is an approach increasingly used in classifying high spatial resolution remote sensing images. Object based image classifiersfirst segment an image into objects (or image segments), and then classify these objects based on their attributes and spatial relations. Numerous algorithms exist for the first step of the OBIA process, i.e. image segmentation. However, less research has been conducted on the object classification part of OBIA, in particular the spatial relations between objects that are commonly used to construct rules for classifying image objects and refining classification results. In this paper, we establish a context where objects are areal (not points or lines) and non-overlapping (we call this “single-valued” space), and propose a framework of binary spatial relations between segmented objects to aid in object classification. In this framework, scaledependent “line-like objects” and “point-like objects” are identified from areal objects based on their shapes. Generally, disjoint and meet are the only two possible topological relations between two non-overlapping areal objects. However, a number of quasitopological relations can be defined when the shapes of the objects involved are considered. Some of these relations are fuzzy and thus quantitatively defined. In addition, we define the concepts of line-like objects (e.g. roads) and point-like objects (e.g. wells), and develop the relations between two line-like objects or two point-like objects. For completeness, cardinal direction relations and distance relations are also introduced in the proposed context. Finally, we implement the framework to extract roads and moving vehicles from an aerial photo. The promising results suggest that our methods can be a valuable tool in defining rules for object based image analysis. Published by Elsevier B.V. on behalf of International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).

A UAV-based photogrammetric mapping system for road condition assessment

Abstract: We present an Unmanned Aviation Vehicle-based Photogrammetric mapping system in this paper. This work is part of a project monitoring of unpaved road condition using remote sensing and other technology, sponsored by the US Department of Transportation. The system is based on a low cost model helicopter equipped with a GPS/IMU and a geomagnetic sensor to detect the position, attitude and velocity of the helicopter. An autonomous controller was employed to control helicopter to fly along a predefined flight path and reach the desired positions. At the ground station, a computer was used to communicate with the helicopter in real-time to monitor flight parameters and send out control commands. The entire processing system includes camera calibration, integrated sensor orientation, digital 3D road surface model and orthoimage generation, automated feature extraction and measurement for road condition assessment. In this paper, both the project and the system architecture are described, and the recent development results are presented.

A Permanent Test Field for Digital Photogrammetric Systems

Abstract: Comprehensive field-testing and calibration of digital photogrammetric systems are essential to characterize their performance, to improve them, and to be able to use them for optimal results. The radiometric, spectral, spatial, and geometric properties of digital systems require calibration and testing. The Finnish Geodetic Institute has maintained a permanent test field for geometric, radiometric, and spatial resolution calibration and testing of high-resolution airborne and satellite imaging systems in Sjokulla since 1994. The special features of this test field are permanent resolution and reflectance targets made of gravel. The Sjokulla test field with some supplementary targets is a prototype for a future photogrammetric field calibration site. This article describes the Sjokulla test field and its construction and spectral properties. It goes on to discuss targets and methods for system testing and calibration, and highlights the calibration and testing of digital photogrammetric systems.

Digital 3D modelling of dinosaur footprints by photogrammetry and laser scanning techniques: integrated approach at the Coste dell'Anglone tracksite (Lower Jurassic, Southern Alps, Northern Italy)

Abstract: Museo Tridentino di Scienze Naturali, Via Calepina 14, 38100 Trento, Italy Dipartimento di Scienze della Terra, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy Dipartimento di Geoscienze, Università degli Studi di Padova, Via Giotto 1, 35137 Padova, Italy Servizio Geologico Provincia Autonoma di Trento, Via Roma 50, 38100 Trento, Italy Fondazione Bruno Kessler, Via Santa Croce 77, 38100 Trento, Italy Institute of Geodesy and Photogrammetry, ETH Hönggerberg, 8093 Zürich, Switzerland Corresponding author e-mail: fabio.petti@mtsn.tn.it

Photogrammetric processing of rover imagery of the 2003 Mars Exploration Rover mission

Abstract: In the 2003 Mars Exploration Rover (MER) mission, the twin rovers, Spirit and Opportunity, carry identical Athena instrument payloads and engineering cameras for exploration of the Gusev Crater and Meridiani Planum landing sites. This paper presents the photogrammetric processing techniques for high accuracy topographic mapping and rover localization at the two landing sites. Detailed discussions about camera models, reference frames, interest point matching, automatic tie point selection, image network construction, incremental bundle adjustment, and topographic product generation are given. The developed rover localization method demonstrated the capability of correcting position errors caused by wheel slippages, azimuthal angle drift and other navigation errors. A comparison was also made between the bundle-adjusted rover traverse and the rover track imaged from the orbit. Mapping products including digital terrain models, orthophotos, and rover traverse maps have been generated for over two years of operations, and disseminated to scientists and engineers of the mission through a web-based GIS. The maps and localization information have been extensively used to support tactical operations and strategic planning of the mission.

Photogrammetric and lidar data integration using the centroid of a rectangular roof as a control point

Abstract: The integration of photogrammetric images and lidar data is becoming a powerful procedure that can be applied in the optimisation of photogrammetric mapping techniques. The complementary nature of lidar and photogrammetric data optimises the performance of many procedures used to extract 3D spatial information from data. For example, photogrammetric imagery enables the accurate extraction of building borders and lidar provides accurate 3D points that give information on the physical surfaces of buildings. These properties demonstrate the usefulness of combining the two types of data to achieve a more robust and complete reconstruction of 3D objects. Photogrammetric procedures require the exterior orientation parameters (EOPs) of the images to extract mapping information. Despite the availability of GPS/INS systems, which greatly assist in direct georeferencing of the imagery, the majority of commercially available photogrammetric systems require control information in order to carry out photogrammetric mapping. Due to improvements in the accuracy of lidar systems in recent years, lidar data is considered a viable source of photogrammetric control. Point features are the principal source of control for photogrammetric triangulation, although linear features and planar patches have also been used. This paper presents a method of georeferencing photogrammetric images using lidar data. The method uses the centroids of rectangular building roofs as control points in the photogrammetric procedure. The centroid of a rectangular building roof derived using lidar data is equivalent to a single control point with 3D coordinates, and can therefore be used in traditional photogrammetric systems. Two photogrammetric experiments were carried out to verify the feasibility of the methodology. The results obtained from these experiments confirm the feasibility of applying the proposed methodology to the georeferencing of photogrammetric images using lidar data.

Geometric accuracy assessment of the orthorectification process from very high resolution satellite imagery for Common Agricultural Policy purposes

Abstract: This study has, as its main aim, the assessment of different sensor models to achieve the best geometric accuracy in orthorectified imagery products obtained from IKONOS Geo Ortho Kit and QuickBird basic imagery. The final orthoimages are compared, both geometrically and visually, with the panchromatic orthophotos based on a photogrammetric flight with an approximate scale of 1 : 20 000, which are now used for the European Union Common Agricultural Policy in Andalusia (Spain). Two-dimensional root mean square (RMS2d) errors in independent check points are used as accuracy indicators. The ancillary data were generated by high accuracy methods: (1) check and ground control points (GCPs) were measured with a differential global positioning system and (2) an accurate digital elevation model was used for image orthorectification. Two sensor models were used to correct the satellite data: (1) a three-dimensional (3D) rational function refined by the user with zero-(RPC0) or first-(RPC1) order polynomial adjustment and (2) the 3D Toutin physical model (CCRS). For the IKONOS image, the best results in the final orthoimages (RMS2d of about 1.15 m) were obtained when the RPC0 model was used. Neither a large number of GCPs (more than nine), nor a better distribution of them, improved the results obtained with the RPC0. For the QuickBird image, the CCRS model generated the best results (RMS2d of about 1.04 m), although it was sensitive to the number and distribution of the GCPs used in its computation.

High-resolution spatial analysis of mountain landscapes using a low-altitude remote sensing approach

Abstract: Mountain landscapes are characterized by great spatial diversity. One basic problem is that there are few high-resolution data for secluded mountain areas. We present a new approach towards topographic mapping and vegetation monitoring: low-altitude remote sensing using Kite Aerial Photography (KAP). The study was conducted in the Norwegian mountains above the treeline. We assessed this approach under specific alpine circumstances. Following the collection of data, we derived a digital elevation model (DEM) from two overlapping images. The model was evaluated by the statistical correlation of 265 random field points and extracted heights from (i) linear contour line interpolation of a topographic map of scale 1 : 50 000, (ii) photogrammetric analysis of kite aerial photographs, and (iii) kriging interpolation of approximately 1000 measured field points. Finally, the vegetation was classified, using both supervised and unsupervised methods. The accuracy of the classification results was evaluated by comparing 265 random points, derived from terrestrial mappings, to classified vegetation types by an error matrix. The generation of derived data compared well with data obtained from high-resolution field surveys and was better than data derived from public-domain government cartography and moderate-scale satellite remote sensing data. Our results demonstrate the economic and logistic advantages of this new KAP-based methodology. The flexibility and outstanding high resolution of our new low-altitude remote sensing approach proved to be particularly suitable for closing the gap between terrestrial investigations and high-altitude remote sensing. Hence, our KAP approach addresses the challenge of multiscale research in mountain landscapes.

Using digital images to reconstruct three-dimensional biological forms: a new tool for morphological studies

Abstract: We examined two image-based methods, photogrammetry and stereo vision, used for reconstructing the threedimensional form of biological organisms under field conditions. We also developed and tested a third ‘hybrid’ method, which combines the other two techniques. We tested these three methodologies using two different cameras to obtain digital images of museum and field sampled specimens of giant tortoises. Both the precision and repeatability of the methods were assessed statistically on the same specimens by comparing geodesic and Euclidean measurements made on the digital models with linear measurements obtained with caliper and flexible tape. We found no substantial difference between the three methods in measuring the Euclidean distance between landmarks, but spatially denser models (stereo vision and ‘hybrid’) were more accurate for geodesic distances. The use of different digital cameras did not influence the results. Image-based methods require only inexpensive instruments and appropriate software, and allow reconstruction of the three-dimensional forms (including their curved surfaces) of organisms sampled in the field. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95, 425–436.