Showing papers in "Isprs Journal of Photogrammetry and Remote Sensing in 2000"

State-of-the-art of elevation extraction from satellite SAR data

Abstract: Relative or absolute elevation extraction from satellite radar data has been an active research topic for more than 20 years. Various investigations have been made on different methods depending on the predominant “fashion” and data availability, leading each time to new developments to improve the capability and the applicability of each method. The paper presents an update of the state-of-the-art of elevation extraction from satellite SAR data. The performance and limitations of four different methods (clinometry, stereoscopy, interferometry and polarimetry) are reviewed, as well as their applicability to different satellite SAR sensors. Their advantages and disadvantages and how they are addressed during the data processing are also analysed. Finally, concluding remarks look at the complementarity aspects of each method to make the best use of the existing and future radar data for elevation extraction.

Automated reconstruction of 3D scenes from sequences of images

Abstract: Modelling of 3D objects from image sequences is a challenging problem and has been an important research topic in the areas of photogrammetry and computer vision for many years. In this paper, a system is presented which automatically extracts a textured 3D surface model from a sequence of images of a scene. The system can deal with unknown camera settings. In addition, the parameters of this camera are allowed to change during acquisition (e.g., by zooming or focusing). No prior knowledge about the scene is necessary to build the 3D models. Therefore, this system offers a high degree of flexibility. The system is based on state-of-the-art algorithms recently developed in computer vision. The 3D modelling task is decomposed into a number of successive steps. Gradually, more knowledge of the scene and the camera setup is retrieved. At this point, the obtained accuracy is not yet at the level required for most metrology applications, but the visual quality is very convincing. This system has been applied to a number of applications in archaeology. The Roman site of Sagalassos (southwest Turkey) was used as a test case to illustrate the potential of this new approach.

Modelling and representation issues in automated feature extraction from aerial and satellite images

Abstract: New digital systems for the processing of photogrammetric and remote sensing images have led to new approaches to information extraction for mapping and Geographic Information System (GIS) applications, with the expectation that data can become more readily available at a lower cost and with greater currency. Demands for mapping and GIS data are increasing as well for environmental assessment and monitoring. Hence, researchers from the fields of photogrammetry and remote sensing, as well as computer vision and artificial intelligence, are bringing together their particular skills for automating these tasks of information extraction. The paper will review some of the approaches used in knowledge representation and modelling for machine vision, and give examples of their applications in research for image understanding of aerial and satellite imagery.

Monitoring the thermal deformation of steel beams via vision metrology

Abstract: The multi-epoch deformation monitoring of a series of super-hot steel beams by digital close-range photogrammetry is reported An on-line configuration of three CCD cameras was established to measure both stable reference points and targets subject to positional displacement Measurements for each beam were conducted at 70–80 epochs over 2 h as the steel cooled from 1100°C to near room temperature Special targeting was required to accommodate the changing colour of the beams from white-hot to brown as they cooled and ensure target survival through a large temperature range A computational approach was employed whereby the photogrammetric triangulation process for any given recording epoch utilised all images obtained up until that time The paper discusses all aspects of the project in which seven beams were monitored to a dimensional tolerance of close to 1 mm (RMS 1-sigma)

A framework for the modelling of uncertainty between remote sensing and geographic information systems

Abstract: This paper addresses the modelling of uncertainty in an integrated geographic information system (GIS), specifically focused on the fusion of activities between GIS and remote sensing. As data is abstracted from its ‘raw’ form to the higher representations used by GIS, it passes through a number of different conceptual data models via a series of transformations. Each model and each transformation process contributes to the overall uncertainty present within the data. The issues that this paper addresses are threefold. Firstly, a description of various models of geographic space is given in terms of the inherent uncertainty characteristics that apply; this is then worked into a simple formalism. Secondly, the various transformation processes that are used to form geographic classes or objects from image data are described, and their effects on the uncertainty properties of data are stated. Thirdly, using the formalism to describe the transformation processes, a framework for the propagation of uncertainty through an integrated GIS is derived. By way of a summary, a table describing sources of accumulated uncertainty across four underlying models of geographic space is derived.

Design and implementation of a computational processing system for off-line digital close-range photogrammetry

Abstract: Through the adoption of recent innovations in automation in vision metrology, it can be demonstrated that rigorous, yet user-friendly digital photogrammetric processes of calibration and orientation/triangulation can be incorporated into a computational scheme which is on the one hand capable of meeting the demands of high metric quality, while on the other offering the facilities necessary to support wider application by non-specialist users. The software system Australis, developed for image mensuration and restitution of off-line close-range photogrammetric networks, is featured to illustrate these processes and procedures. By describing the structure and components of Australis, the authors aim to demonstrate that many processes which have on occasion been viewed to be the exclusive province of automated, high-precision vision metrology are indeed suited to more general application across a broad range of fields which involve 3D object recording via close-range imagery.

Real world modelling through high resolution digital 3D imaging of objects and structures

Abstract: This paper summarises the results achieved from a number of laser scanning experiments performed in our laboratories and on remote sites. The potential of this technology for imaging applications and as an input to virtualised reality environments is discussed. Parameters to be considered for this type of activity are related to the design of laser scanners with adequate depth of field, image resolution, shape reproduction fidelity, registered colour information, robustness to ambient light interference and scanning strategies. The first case reviewed is an application geared towards improving access to art collections belonging to museums. A number of digital 3D models acquired in Italy in 1997–1998 are presented, e.g. marble statue from G. Pisano (circa 1305). The second case aims at digitising large structures. Examples of a large sculpture located outside of the Canadian Museum of Civilisation in Hull, Canada and the Orbiter Docking System (ODS) located at the Kennedy Space Center in Florida, are presented.

Location similarity of regions

Abstract: This article gives a systematic investigation of location-based similarity between regular regions. Starting from reasonable conditions for such measures, it is shown that there is only a finite number of location properties to be compared. The complete set of combinations is presented, and their behaviour and interpretability are discussed. Similarity measures are needed for all kinds of matching problems, including merging spatial data sets, change detection, and generalization. However, the measures are empirical measures. Therefore, measures found in literature seem to be chosen at random. With this synopsis, I show the differences of behaviour for all available choices.

Suitability of the DCS460c colour digital camera for quantitative remote sensing analysis of vegetation

Abstract: The Kodak DCS460c is a high resolution, colour digital camera with a specific CCD array mosaic structure that requires a dedicated processing algorithm for production of a three-band image. Kodak's Active Interpolation (KAI) algorithm is compared with a simpler nearest neighbour interpolation method (NNI) with regard to applicability in scientific investigations of target features in imagery. Detailed quantitative analyses of flat-field imagery were undertaken in order to provide insight into artefacts and to correct for the off nadir reduction in brightness. Characteristics of the aerial photography were also studied and aspects of processing and analysis of the imagery for scientific investigations are discussed. We present a novel method for correction of brightness fall-off (due to the vignette effects and increasing view angle) which is generally applicable to remote sensing of rural scenes. Quantitative spectral comparisons between related imagery from the DCS460c (e.g. for interpretation of relative vegetation cover) are only scientifically reliable when the raw (i.e. non-interpolated) DN values for green and red are below about 67% of their maximum range. This is due to preferential vertical leakage or charge diffusion in the CCD. A combination of CCD characteristics leads to possibly poor spatial resolution for the infrared band. The imagery after KAI shows good spatial resolution and has a natural looking colour reproduction useful for discerning features by eye. However, when using KAI, reliable spectral measurements can probably only be acquired from portions of objects that are at least four pixels from the object's boundary. In general, quantitative spatial and spectral analyses can be carried out with the DCS460c but the KAI, the broad band response and the vertical leakage require specific solutions to produce quantitative results.

A processing and software system for rice crop inventory using multi-date RADARSAT ScanSAR data

Abstract: An operational crop survey program requires standardised procedures and software packages to meet the specified targets of timeliness and accuracy of estimates. Currently, the focus is to include Synthetic Aperture Radar (SAR) data in such a program, as these data are available from a number of sensors. A procedure has been developed to use multi-date SAR data for rice crop inventory. The steps were packaged together for ease-of-use and with minimal user interaction. The package, SARCROPS, is built around the EASI/PACE software. It is, at present, tuned for RADARSAT ScanSAR data. The package was used during the 1998–1999 and 1999–2000 seasons to estimate the rice area at state level in India with the participation of a number of interdisciplinary users. Around 45 and 89 scenes of ScanSAR data were used during these two seasons, respectively. This paper reports the details of the SARCROPS processing chain.

Fuzzy spatial objects and their dynamics

Abstract: Many monitoring activities of environmental processes deal with phenomena that are fuzzy. Their spatial description cannot be based on the geometry of their boundaries, because these cannot be identified. In fact, such phenomena have an uncertain thematic description and that is often the reason why their spatial extent can only be determined with limited accuracy. We will therefore present in this paper a formalism for the description of objects without fixed boundaries, i.e., objects with a fuzzy spatial extent. A method based on this formalism will be developed for the extraction of fuzzy spatial object data from digital images or from field representations in a raster format. This method can then be used for monitoring purposes when the spatial extent of fuzzy objects are identified at different epochs; the dynamics of such objects can then be obtained from these time series. Several parameters will be proposed to estimate the overlap of objects at successive epochs; with these parameters the state transitions of objects can be evaluated. Several types of state transition can be distinguished with these parameters such as shift, merge, and split of objects. These state transitions can then be combined to form the processes through which the objects evolve over time. The proposed method is applied in a coastal geomorphologic study of a barrier island in The Netherlands.

A digital photogrammetric workstation on the WEB

Abstract: The main features of a WEB-based tool for digital architectural photogrammetry called Architectural Photogrammetry Network Tool for Education and Research (ARPENTEUR) are presented The aim of this project is to propose a photogrammetric software package made freely available on the Internet as an applet through a simple browser ( http://wwwarpenteurnet ) All the photogrammetric adjustment and image processing classes are written in Java™ The use of large applets in photogrammetry has not been very advanced until now but rate transfers and compatibility levels of Internet browsers will increase in the near future Users can set up their own projects by transferring their images, camera, and control information on the ARPENTEUR servers from any place in the world connected on the Internet Various examples of small format architectural photogrammetry projects are also accessible via WWW and can be used for teaching This software is an extension of the Traitement d'Images et Photogrammetrie Numerique (TIPHON) software developed at ENSAIS-LERGEC The photogrammetric model is currently computed by the traditional steps of inner, relative and absolute orientations The measurements in the images can be performed manually or by image correlation The measured points, lines, and geometrical primitives are recorded in text files and visualised inside a standard WEB browser The plotting module is especially dedicated to architectural surveys and based on a formalisation of architectural and geometrical knowledge The latest developments of the Java programming language and object-oriented systems are used in ARPENTEUR, both in the photogrammetric and in the architectural part, and ensure a high level of compatibility with any hardware platform supporting a WEB browser

A robust linear least-squares estimation of camera exterior orientation using multiple geometric features

Abstract: For photogrammetric applications, solutions to camera exterior orientation problem can be classified into linear direct and non-linear. Direct solutions are important because of their computational efficiency. Existing linear solutions suffer from lack of robustness and accuracy partially due to the fact that the majority of the methods utilize only one type of geometric entity and their frameworks do not allow simultaneous use of different types of features. Furthermore, the orthonormality constraints are weakly enforced or not enforced at all. We have developed a new analytic linear least-squares framework for determining camera exterior orientation from the simultaneous use of multiple types of geometric features. The technique utilizes 2Dr3D correspondences between points, lines, and ellipse-circle pairs. The redundancy provided by different geometric features improves the robustness and accuracy of the least-squares solution. A novel way of approximately imposing orthonormality constraints on the sought rotation matrix within the linear framework is presented. Results from experimental evaluation of the new technique using both synthetic data and real images reveal its improved robustness and accuracy over existing direct methods. q 2000 Elsevier Science B.V. All rights reserved.

Towards the global GIS

Abstract: This paper outlines the concept of a “global GIS,” and defines various aspects of its development, as well as various options and decisions that must be made. The emphasis is on the advantages and disadvantages of maintaining a global topological structure, and whether topology should be generated “on the fly” in response to a specific query. We first define what we mean by “space” in this context, followed by a description of topological structures and how we may use them in the context of graph traversal problems. We then describe some appropriate data structures. After mentioning some of the real-world problems associated with polygon construction problems, we touch on how graphs may represent change over time. A global topological structure is then proposed which resolves some of the problems mentioned. This is based on incremental graph updating methods. Some unresolved problems associated with using global topological structures are then discussed, especially those associated with queries, such as polygon overlay, that generate a new local topological structure. We conclude with some preliminary rules, and suggest further work.

Geocoding SAR interferograms by least squares adjustment

Abstract: A geocoding model for Synthetic Aperture Radar (SAR) interferometry based on a least-squares adjustment combining interferometric phase, range, Doppler centroid frequency, flight path and control point data is proposed. The complete mathematical framework for the computation of object space coordinates without approximations is presented. It provides a way to an efficient implementation of the algorithm for geocoding the pixels of an interferogram. The method is preferably applicable to spaceborne dual-pass interferometry, and independent of the orbit configuration. An accuracy analysis of object point positioning is conducted and results of geocoding an ERS tandem interferogram are shown.

Contributions to a quality description of areal objects in spatial data sets

Abstract: In this paper, we present a quality evaluation of two-dimensional building acquisition. We propose methods for identification and quantification of differences between independently acquired regions, and we present a systematic classification of those differences. Differences between acquired sets Rj={ri}j of region rij depend on the context of observation, on the technique of observation, etc. We distinguish topological and geometrical differences. Topological differences refer to the interior structure of a set of regions as well as to the structure of the boundary of a single region. Geometrical differences refer to the location of the boundary of a single region or of a set of regions, independent of their representation and of the structure of the boundaries. Identification of differences requires a matching of two data sets R1 and R2, which is done here by weighted topological relationships. For the identification of topological differences between two sets R1 and R2 of regions, we use the two region adjacency graphs (RAGs). For an identification of geometrical differences, we use the zone skeleton between two matched subsets rp1 and rq2 of the given sets. The zone skeleton is labeled with the local distances of the corresponding boundaries of the subsets; especially, we investigate its density function. An example based on two real data sets of acquired ground plans of buildings, shows the feasibility of the approach.

How well do we understand Earth observation electro-optical sensor parameters?

Abstract: Since the launch of LANDSAT-1, the Earth observation systems' capability and utilisation has increased substantially. The past decade has seen a number of remote sensing satellites with improved capabilities. Understanding the sensor parameters from a user's standpoint is not that easy. In the context of increasing relevance and dependence on fusion of data from various sensors, there is an urgent need to standardise the sensor parameters specified. The present paper is an attempt to raise some of the concerns regarding specifying spatial, radiometric, spectral and temporal resolution. I solicit inputs from the readers on the points raised to formulate a consolidated recommendation for the ISPRS Council to propose to the international community.

Geometric in-flight calibration of the stereoscopic line-CCD scanner MOMS-2P

Abstract: This paper describes the geometric in-flight calibration of the Modular Optoelectronic Multispectral Scanner MOMS-2P, which has collected digital multispectral and threefold along-track stereoscopic imagery of the earth's surface from the PRIRODA module of the Russian space station MIR from October 1996 to August 1999. The goal is the verification and, if necessary, the update of the calibration data, which were estimated from the geometric laboratory calibration. The paper is subdivided into two parts, describing two different procedures of geometric in-flight calibration. The first method is based on DLR matching software and is restricted to nadir looking channels, which are read out simultaneously. From a high number of individual point matches between the images of the same area taken by the different CCD arrays, the most reliable ones are selected and used to calculate shifts with components in and across flight direction between the CCD arrays. These actual shifts are compared to the nominal shifts, derived from the results of the laboratory calibration, and parameters of the valid camera model are estimated from both data sets by least squares adjustment. A special case of band-to-band registration are the two optically combined CCD-arrays of the nadir high-resolution channel. They are read out simultaneously with a nominal 10 pixel overlap in stereoscopic imaging mode A. The DLR matching software is applied to calculate the displacement vector between the two CCD-arrays. The second method is based on combined photogrammetric bundle adjustment using an adapted functional model for the reconstruction of the interior orientation. It requires precise and reliable ground control information as well as navigation data of the navigation-package MOMS-NAV. Nine contiguous image scenes of MOMS-2P data-take T083C building an about 550-km-long strip over southern Germany and Austria taken in March 1997 were evaluated. From both procedures calibration data are estimated, which are presented and compared to the lab-calibration results.

Taxonomy of space tessellation

Abstract: When we map an area or create a digital database for it, the first task is often to partition the space into smaller units. There are traditionally two methods of partitioning: vector and raster. A vector partition delineates the boundary of features by polylines while a raster partition subdivides the space into a regular matrix of square or rectangular pixels. These two are complementary methods of subdividing the space either by features or by unconstrained space cells. In the third dimension, they are extended to polyhedra and voxels, respectively. We will argue in this paper that the terms “vector” and “raster” cannot describe all cases of tessellation. With advances in data modelling, variations of the two traditional methods have been developed, such as the representation of a feature by pixels and not by polylines. At present, there is a lack of systematic terminology to describe the various methods of tessellation. In this paper, we will propose a taxonomy for three-dimensional space tessellation. Its essential feature is to distinguish between abstract concepts of tessellation and their encoding methods. We recognise that tessellation of geographic space is carried out in different stages with increasingly precise mathematical meaning. This provides us with an insight into the process of spatial tessellation and a model to systematically describe the various structures. These concepts could form a basis for spatial data models.

Theme Issue on dynamic and multi-dimensional GIS

Abstract: This is a collection of papers originally presented at two international conferences. One of them was the International Workshop on Dynamic and MultiDimensional GIS, which was organised in August 1997 in Hong Kong by Y.C. Lee and Zhi-Lin Li of the Hong Kong Polytechnic University. The other one was the Symposium of ISPRS Commission IV, which was organised in September 1998 in Stuttgart by Dieter Fritsch of Stuttgart University. The ISPRS Working Group IVrIII.1 AGIS Fundamentals and Spatial DatabasesB was responsible for several sessions in both meetings. The articles published in this issue of the ISPRS Journal are a selection of the papers presented in those sessions. Although these papers have been previously published in the respective proceedings, they appear here in this theme issue much revised and expanded. Ž . Geographic Information Systems GIS have evolved from simple two-dimensional map drafting systems in the early 1960s to fairly sophisticated information systems for spatial data of the present day. Two keywords often used to describe current Ž GIS or more accurately a vision of the AultimateB . GIS are dynamic and multi-dimensional. By dynamic, we imply the ability of the system to capture the ever-changing world, and by multi-dimensional, we mean the liberation of spatial data from the confines of the two-dimensional space of traditional maps. When we go beyond the third dimension, we often think of time, an important attribute of a dynamic system. However, a multi-dimensional GIS does not necessarily contain time as one of its coordinates. In fact, a multi-attribute database in the traditional sense is multi-dimensional, if we consider each attribute as a co-ordinate in some kind of space. Two papers in this issue have addressed the space issue and the tessellation of space into manageable units of interest to GIS applications. Lee proposes a taxonomy of space tessellation and examines the process of abstracting real-world objects into different kinds of space when creating a spatial database. Gold, on the other hand, looks at space from a topological perspective and argues that a tessellation of the world and its features into Voronoi polygons Ž . or its dual of Delaunay triangles could create a global topological space. Real-world objects and phenomena are not only dynamic but also fuzzy in definition. Molenaar and Cheng address the dynamics of fuzzy objects. They developed formalism for their description and a method to identify these objects and their evolution in time. GIS databases evolve not only because the world is changing, but also as a result of operations performed on them over time. Gahegan and Ehlers examine how the quality of spatial data evolves when it is transformed from raw image data collected by remote sensing satellites to geo-referenced and interpreted data stored in spatial databases. They suggest that such a transformation would go through Ž three operations image capture, image classification, . and object formation and document the error sources and their effects on these operations. Modelling how features change is one thing, but detecting if they have changed is sometimes a more difficult and expensive task in practice. Winter exŽ . amines the location similarity or dissimilarity of discrete spatial objects that could represent an object that has evolved with time or two objects from different sources not of the same quality. He proposes seven measures that are symmetric, nor-

Space education in developing countries in the information era, regional reality and new educational material tendencies: example, South America

Abstract: The initial activities on space education began right after World War II, in the early 1950s, when USA and USSR started the Space Race. At that time, Space education was only and exclusively available to researchers and technicians working directly in space programs. This new area was restricted only to post-graduate programs (basically master and doctoral degree) or to very specific training programs dedicated for beginners. In South America, at that time there was no kind of activity on space education, simply because there was no activity in space research. In the beginning of the 1970s, Brazil, through INPE, had created masteral and doctoral courses on several space areas such as remote sensing and meteorology. Only in the mid-1980s did Brazil, after a UN request, create its specialisation course on remote sensing dedicated to Latin American professionals. At the same period, the Agustin Codazzi Institute (Bogota, Colombia) began to offer specialisation courses in remote sensing. In South America, educational space programs are currently being created for elementary and high schools and universities, but the author personally estimates that 90% of these educational programs still make use of traditional educational materials — such as books, tutorials, maps and graphics. There is little educational material that uses multimedia resources, advanced computing or communication methods and, basically, these are the materials that are best suited to conduct instructions in remote sensing, GIS, meteorology and astronomy.

Report on the ISPRS Journal of Photogrammetry and Remote Sensing (PRS) for the period 1996–2000

Abstract: This report was presented by the author, as Editor-in-Chief (EIC) of PRS, to the General Assembly of the Delegates of the ISPRS Members during the 19th ISPRS Congress, Amsterdam, 16–23 July 2000. Since it summarises in quite some detail many new developments since the last Congress that are of interest not only to ISPRS in general, but also to authors and readers, a slightly modified version of this report is published here.