Conference Report

ISPRS WORKSHOP ON 3D RECONSTRUCTIONFROM LASER SCANNER AND INSAR DATA

This ISPRS Commission III/3 Workshop was held in Dresden, Germany, from 8th to10th October 2003. Within Commission III, which is concerned with Theory andAlgorithms, Working Group 3 focuses on automatic 3D reconstruction of objects fromboth airborne laser scanning and interferometric synthetic aperture radar (InSAR) data.The aim of the workshop was to provide an overview of the most recent developmentsin the field by bringing together users, researchers, developers and data providers.

The workshop was hosted by the Technical University of Dresden. The city,which is historically synonymous with both splendour and apocalyptic tragedy, provedto be a most attractive venue, with the workshop’s evening receptions and guided toursof the city and environs allowing the participants to absorb some of the metropolis’history. The blend of historic buildings along the Elbe and the contemporaryconstruction of some truly striking buildings have led to recent propositions thatDresden is fast becoming one of Germany’s most attractive cities. Perhaps it was forthis reason that the workshop was inundated with participants—110 from 20countries—which far exceeded anticipated numbers. However, I would suggest thepopularity of this workshop was more a function of the recent expansion of the use oflaser scanning, with the setting of Dresden providing a bonus attraction!

The huge attendance at the workshop was in proportion to the developments inthe field of reconstruction and modelling from laser scanning and InSAR data. Suchproliferation of laser scanning applications led John Trinder, President of ISPRS, toquestion in his opening speech whether the use of traditional film in photogrammetry isbecoming obsolete. He documented the recent rise of laser scanning over image-basedmethods, attributing the adoption of laser scanning techniques to both economics andthe accuracies which can be achieved. However, this was qualified with a suggestionthat laser scanning data still exhibits limitations which can perhaps be overcomethrough data fusion to improve, for example, planimetric accuracies. Trinder closed hisspeech with a suggestion regarding the direction for future developments in laserscanning. He proposed that we may see real-time data processing on sensor platformsin future years, and that this, combined with automation of classification/featureextraction, will further increase the attraction of laser scanning data for 3Dreconstruction. A second welcome to the workshop was offered by Andre Streilein(Switzerland and EuroSDR)17 , who echoed Trinder’s call for data integration as amethod for optimisation of modelling.

The quality of presentations which followed was very high, and was achievedthrough a double-blind review process for the submission of papers to the workshop.

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The 25 accepted papers were divided between seven oral sessions and a poster sessionwhich contained a further 12 accepted submissions. The workshop was carefullystructured to cover current topics of interest, such as accuracy, forestry applications,filtering algorithms, building reconstruction, data fusion and mapping. This structureoffered a refreshing departure from the more traditional emphasis on buildingreconstruction methodologies which have tended to dominate research in this field dueprincipally to the heavy demand for this research. The wide variety of research topicshighlighted the utility and transferability of laser scanning and InSAR data,emphasising the potential for achieving the ‘‘capture once, use many times’’ ethoswhich so many organisations strive for.

It is impossible to mention all of the presentations at the workshop in this shortarticle, however, a number of papers stimulated much interest and debate and arementioned below.

The importance of the accuracy of laser scanning data has become increasinglyprominent in recent conferences, perhaps indicated here by assigning the openingsession to this topic. Frederic Bretar18 (IGN, France) offered a novel method formatching laser data strips with photogrammetric data by determining local translationsin order to estimate global deformations. Such research will become increasinglyimportant given the current interest in data fusion. The following session on forestryand segmentation of data for extraction of trees demonstrated the wide use of laserscanning as a tool for research in this area. In addition to suggested methods for theextraction of trees, a number of presentations indicated specific economic uses for suchmodels, such as estimations of timber volume.

The topic of strip adjustment and calibration of laser scanner data continues to beof fundamental importance in this field of research. Rolf Katzenbeißer19 (TopoSysGmbH, Germany) suggested that whilst laser scanning is the most efficient method fordigital elevation model (DEM) acquisition, the sources of error—including stripadjustment problems—are distracting potential customers. This highlighted theimportance of research into this area, and a number of papers at the workshop offerednew methods of identifying and eliminating or reducing error.

Of great interest to many was the session on filtering, and particularly noteworthywas George Sithole’s20 (TU Delft, the Netherlands) paper in which he compared anumber of filtering algorithms. Direct comparisons of algorithms are extremely rare,and the utility of this comparison was widely noted at the conference. The paperstimulated much discussion and provided a focal point both for the filtering session andduring subsequent coffee breaks. The following session on building reconstruction alsooffered some excellent material including a paper from Gunho Sohn21 and Ian Dowman21,2221,22(UCL, UK) who have investigated the automatic identification and representation ofbuilding objects from lidar and Ikonos imagery. This topic of data fusion was alsodiscussed by Franz Rottensteiner23 (UNSW, Australia), and, in a later session, by BenoıtSt-Onge (University of Quebec in Montreal, Canada)24 . Two papers in this session alsodealt with the extraction of buildings from InSAR data, and discussed how some of theproblems inherent in this data source can be overcome. However, the majority ofresearch presented at the workshop focused on the capabilities of laser scanning forapplications such as building, tree and road modelling, with a number of papersoffering interesting new approaches for object reconstruction.

In summary, the quality and range of presentations was excellent and wascomplemented by an exhibition by 10 participating companies which ran

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simultaneously with the workshop. This was an excellent idea, and really providedfocus for discussion during coffee breaks. It also permitted the successful marrying ofthe commercial and the research laser scanning communities, and provided a greatopportunity for networking.

The workshop was a great success. It provided a valuable opportunity for all thoseinvolved in the laser scanning and InSAR communities to come together to shareresearch ideas and to progress projects. It appealed to a wide variety of people, fromthe veterans of laser scanning research to those on fact-finding missions using theworkshop to learn the basics. The fact that the workshop satisfied such a wide varietyof needs is testament to the administration and enthusiasm of the organisers, Hans-Gerd Maas, George Vosselman, Andre Streilein and their helpers. For those whomissed this excellent event, the proceedings from the workshop are available on theISPRS server (http://www.isprs.org/commission3/wg3/workshop_laserscanning/).

Sarah L. Smith

Ordnance Survey

76 � 2004 The Remote Sensing and Photogrammetry Society and Blackwell Publishing Ltd.

Smith. ISPRS Workshop on 3D Reconstruction from Laser Scanner and InSAR Data