Thomas Krauß | German Aerospace Center (DLR) (original) (raw)

Papers by Thomas Krauß

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2017

Automatic rooftop extraction is one of the most challenging problems in remote sensing image anal... more Automatic rooftop extraction is one of the most challenging problems in remote sensing image analysis. Classical 2D image processing techniques are expensive due to the high amount of features required to locate buildings. This problem can be avoided when 3D information is available. In this paper, we show how to fuse the spectral and height information of stereo imagery to achieve an efficient and robust rooftop extraction. In the first step, the digital terrain model (DTM) and in turn the normalized digital surface model (nDSM) is generated by using a newly step-edge approach. In the second step, the initial building locations and rooftop boundaries are derived by removing the low-level pixels and high-level pixels with higher probability to be trees and shadows. This boundary is then served as the initial level set function, which is further refined to fit the best possible boundaries through distance regularized level-set curve evolution. During the fitting procedure, the edge-based active contour model is adopted and implemented by using the edges indicators extracted from panchromatic image. The performance of the proposed approach is tested by using the WorldView-2 satellite data captured over Munich.

Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVIII, 2012

ABSTRACT Using the capability of WorldView-2 to acquire very high resolution (VHR) stereo imagery... more ABSTRACT Using the capability of WorldView-2 to acquire very high resolution (VHR) stereo imagery together with as much as eight spectral channels allows the worldwide monitoring of any built up areas, like cities in evolving states. In this paper we show the benefit of generating a high resolution digital surface model (DSM) from multi-view stereo data (PAN) and fusing it with pan sharpened multi-spectral data to arrive at very detailed information in city areas. The fused data allow accurate object detection and extraction and by this also automated object oriented classification and future change detection applications. The methods proposed in this paper exploit the full range of capacities provided by WorldView-2, which are the high agility to acquire a minimum of two but also more in-orbit-images with small stereo angles, the very high ground sampling distance (GSD) of about 0.5 m and also the full usage of the standard four multispectral channels blue, green, red and near infrared together with the additional provided channels special to WorldView-2: coastal blue, yellow, red-edge and a second near infrared channel. From the very high resolution stereo panchromatic imagery a so called height map is derived using the semi global matching (SGM) method developed at DLR. This height map fits exactly on one of the original pan sharpened images. This in turn is used for an advanced rule based fuzzy spectral classification. Using these classification results the height map is corrected and finally a terrain model and an improved normalized digital elevation model (nDEM) generated. Fusing the nDEM with the classified multispectral imagery allows the extraction of urban objects like like buildings or trees. If such datasets from different times are generated the possibility of an expert object based change detection (in quasi 3D space) and automatic surveillance will become possible.

Citeseer

ABSTRACT: The GMES (Global Monitoring for Environment and Security) Fast Track Land monitoring Se... more ABSTRACT: The GMES (Global Monitoring for Environment and Security) Fast Track Land monitoring Service (FTLS) is a service to provide on a regular basis land cover and land use change datasets, which can be used by a wide range of downstream services at ...

Currently available very high resolution space borne imagery can be used for mapping and 3D model... more Currently available very high resolution space borne imagery can be used for mapping and 3D modeling of archaeologic sites and monuments from all over the world. This allows also the continuous monitoring, protection from natural and human threatening and may also be the base for virtual or real reconstruction of monuments. As an example it is shown how a mostly automatic approach for operationally monitoring from space may work on the example of the world heritage site of Palmyra, Syria

This article shows first results of implementing a method for creating DEMs from high resolution ... more This article shows first results of implementing a method for creating DEMs from high resolution satellite imagery based on dynamic programming. The herein described DTW algorithm maps epipolar stereo image pairs line by line on top of each other using a method similar to dynamic time warping which is a common approach in speech recognition. The DTW algorithm is described and applied to several test images. The resulting DEMs and pros and cons of this method are shown and discussed. 1

In this article an attempt for improving an existing method creating DEMs fully automatically fro... more In this article an attempt for improving an existing method creating DEMs fully automatically from stereoscopic image pairs is presented. Results applying this method to very high resolution (VHR) satellite imagery is shown. The herein discussed “column” algorithm is illustrated in brief and compared to a conventional algorithm frequently used in generating DEMs from satellite line scanner data. The presented algorithm is producing DEMs with an improved matching of steep objects as can be found in urban satellite imagery but introduces also some blunders in the generated DEMs. 1.

Remote Sensing for Archaeology and Cultural Landscapes, 2019

Change detection using remote sensing data is one of the most essential processing steps for moni... more Change detection using remote sensing data is one of the most essential processing steps for monitoring urban and forest areas. And it provides an invaluable tool for archaeological sites in times of war or natural disasters. However, until now the visual interpretation is still the main technique in analyzing changes from these images. In this chapter, the state of the art of the change detection on archaeology applications and the latest change detection techniques in 2D and 3D are introduced.

The project aims to establish a "Remote Sensing Science Center for Cultural Heritage" i... more The project aims to establish a "Remote Sensing Science Center for Cultural Heritage" in Cyprus. The Center foresees to support the current Cultural Heritage (CH) needs through the systematic exploitation of Earth Observation technologies. For the establishment of the center, the existing Remote Sensing and Geo-Environment Research Laboratory of the Eratosthenes Research Center (ERC) based at the Cyprus University of Technology (CUT), is twinned with internationally-leading counterparts from the EU, the National Research Council of Italy (CNR, through IMAA and IBAM) and the German Aerospace Centre (DLR). Through this network, the ATHENA twinning project strengthens the remote sensing capacity in cultural heritage at CUT's ERC. The ATHENA project aim is knowledge transfer, achieved primarily through intense training activities (including virtual training courses, workshops and summer schools) with an ultimate scope to enhance the scientific profile of the research staff...

In this study a method for automatic detection and vulnerability estimation for areas endangered ... more In this study a method for automatic detection and vulnerability estimation for areas endangered by heavy rains was developed. The method relies simply only on digital terrain models like SRTM. The presented method for vulnerability analysis is based on different methods and was also applied to different types of DEMs like the freely available SRTM, a 25 m terrain model (DTM) from Germany down to 5 m surface models (DSM) which were derived from satellite images of the Indian Cartosat sensor. For validating the results anonymized data of an insurance company were available. The presented method is finally evaluated using this reference data.

For applications in which an in-situ GNSS measurement is not possible, too laborious or too cumbe... more For applications in which an in-situ GNSS measurement is not possible, too laborious or too cumbersome, modern remote sensing with radar satellites offers a solution. With the help of at least two radar images from the TerraSAR-X or TanDEM-X satellite and the corresponding data processing, it is possible to obtain position information with accuracy in the sub-decimeter range. As a result, a measurement on site is no longer necessary, but can be carried out with the satellites remotely and worldwide. The applications are in the area of geodetic measuring networks and as ground control points for the perfect registration of aerial and satellite images as well as reference points for landmark navigation. However, it must be emphasized that only the position of objects that have a particular radar signature can be determined. These are for example masts of signs, traffic lights or light poles. The 3D-coordinates of the foot point are determined.

This paper presents how the EXSELSIOR H2020 Teaming project will support the management and monit... more This paper presents how the EXSELSIOR H2020 Teaming project will support the management and monitoring of the cultural heritage domain through its research and innovation agenda within the Eastern Mediterranean, Middle East, and North Africa (region known as EMMENA). The pressing need for protecting the cultural heritage assets is highlighted throughout the document by reviewing the conducted research work in key funded projects attained in the past by the Cyprus University of Technology team in collaboration with EXCELSIOR’s partners

IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium, 2019

This paper describes the winning contribution to the 2019 IEEE GRSS Data Fusion Contest Multi-vie... more This paper describes the winning contribution to the 2019 IEEE GRSS Data Fusion Contest Multi-view Semantic Stereo Challenge. In this challenge, a digital surface model (DSM) and a semantic segmentation should be derived from a large number of multi-spectral WorldView-3 images. Results from 50 stereo pairs matched using Semi-Global Matching (SGM) are fused into a DSM. Semantic segmentation is performed with an ensemble of FCN networks taking as input RGB, multi-spectral and height data. Their results are then merged with pixel-wise detectors for the classes water and high vegetation. Compared to the second and third placed teams (mIOU-3 scores of 0.73 and 0.7295), our contribution reached a significantly higher score of 0.745.

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2014

The focal plane assembly of most pushbroom scanner satellites is built up in a way that different... more The focal plane assembly of most pushbroom scanner satellites is built up in a way that different multispectral or multispectral and panchromatic bands are not all acquired exactly at the same time. This effect is due to offsets of some millimeters of the CCD-lines in the focal plane. Exploiting this special configuration allows the detection of objects moving during this small time span. In this paper we present a method for automatic detection and extraction of moving objects – mainly traffic – from single very high resolution optical satellite imagery of different sensors. The sensors investigated are WorldView-2, RapidEye, Pléiades and also the new SkyBox satellites. Different sensors require different approaches for detecting moving objects. Since the objects are mapped on different positions only in different spectral bands also the change of spectral properties have to be taken into account. In case the main distance in the focal plane is between the multispectral and the pan...

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2012

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2014

Developing fully automatic systems is still an active research topic in 3D building model reconst... more Developing fully automatic systems is still an active research topic in 3D building model reconstruction. While a general solution to the building reconstruction problem relies on collecting and grouping the modeling cues (e.g., lines, corners, planes) from Digital Surface Model (DSM) data, failure in finding the cues due to noise in the DSM and the object complexities is a big challenge. In this paper, we introduce a clustering-based method for cue discovery from Pan-chromatic satellite images which reduces the dependencies of the reconstruction techniques on DSM data. Experimental results show that the proposed method is not only able to effectively refine building masks by discriminating building boundaries from nearby clutter, but also is able to determine the roof types (e.g., pitched, flat). The latter, allows to establish a reconstruction method to reduces the search effort and the failure probability regions in finding a particular cue by leading the system to an appropriate...

Earth Resources and Environmental Remote Sensing/GIS Applications VII, 2016

Remote sensing science is increasingly being used to support archaeological and cultural heritage... more Remote sensing science is increasingly being used to support archaeological and cultural heritage research in various ways. Satellite sensors either passive or active are currently used in a systematic basis to detect buried archaeological remains and to systematic monitor tangible heritage. In addition, airborne and low altitude systems are being used for documentation purposes. Ground surveys using remote sensing tools such as spectroradiometers and ground penetrating radars can detect variations of vegetation and soil respectively, which are linked to the presence of underground archaeological features. Education activities and training of remote sensing archaeology to young people is characterized of highly importance. Specific remote sensing tools relevant for archaeological research can be developed including web tools, small libraries, interactive learning games etc. These tools can be then combined and aligned with archaeology and cultural heritage. This can be achieved by presenting historical and pre-historical records, excavated sites or even artifacts under a "remote sensing" approach. Using such non-form educational approach, the students can be involved, ask, read, and seek to learn more about remote sensing and of course to learn about history. The paper aims to present a modern didactical concept and some examples of practical implementation of remote sensing archaeology in secondary schools in Cyprus. The idea was built upon an ongoing project (ATHENA) focused on the sue of remote sensing for archaeological research in Cyprus. Through H2020 ATHENA project, the Remote Sensing Science and Geo-Environment Research Laboratory at the Cyprus University of Technology (CUT), with the support of the National Research Council of Italy (CNR) and the German Aerospace Centre (DLR) aims to enhance its performance in all these new technologies.

Fourth International Conference on Remote Sensing and Geoinformation of the Environment (RSCy2016), 2016

The work presented in this paper shows the possibility of an automatic extraction of three dimens... more The work presented in this paper shows the possibility of an automatic extraction of three dimensional urban objects from very high resolution (VHR) satellite scenes from anywhere of the world. Actual VHR satellites like GeoEye, World-View-2 or 3 or the Pliades system have ground sampling distances (GSD, "pixel sizes") of 0.3 to 0.7 centimetres. All these systems allow also the acquisition of in-orbit-stereo-images. These are two or more images of the same location on ground acquired in the same orbit of the satellite from different viewing angles mostly only some seconds apart. From such stereo or-if more than two images were acquired-multistereo images in a first step a high resolution digital surface model (DSM) can be extracted with the same GSD as the stereo imagery. In the second step the inevitable errors and holes in the generated DSM will be filled and corrected using the multispectral imagery. Beneath the very high resolution panchromatic images which are used for the generation of the DSM also lower resolution-normally about 1/4 of the resolution of the panchromatic bandsmulti-spectral images are acquired. These contain at least the four visible/NIR (VNIR) bands blue, green, red and near-infrared (NIR). Some sensors have more VNIR bands like World-View-2 (coastal, blue, green, yellow, red, red-edge and two NIR bands) or even additionally shortwave -infrared (SWIR) bands like World-View-3. From these mutispectral bands in a third step a spectral classification can be derived. This classification is used mainly for discrimination of vegetation and non-vegetation areas and the detection of water areas. The last step in this pre-processing comprises the correct orthorectification of the DSM and the pan-sharpened multispectral image. After this pre-processing of the stereo-imagery urban objects like buildings, trees, roads, bridges, and so on can be detected and in a last step these objects will be modeled to produce a final object-model of the satellite-scene or parts of it. In this paper the method is described and applied to an example satellite imagery.

The interdisciplinary project "SimWorld" - initiated by the German Aerospace Center (DL... more The interdisciplinary project "SimWorld" - initiated by the German Aerospace Center (DLR) - aims to improve and to facilitate the generation of virtual landscapes for driving simulators. It integrates the expertise of different research institutes working in the field of car simulation and remote sensing technology. SimWorld will provide detailed virtual copies of the real world derived from air- and

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2013

Here we present the operational, fully automatic processing system CATENA developed at DLR. The u... more Here we present the operational, fully automatic processing system CATENA developed at DLR. The uniform pre-processing of an increasing amount of satellite data for generation of whole coverages of e.g. Europe for one time or of time-series for one location covering many years is requested more and more. Such requirements contain the processing of huge amounts of data which can hardly be handled manually. So a fully automatic pre-processing environment was developed at the Remote Sensing Technology Institute of DLR in Oberpfaffenhofen since 2006. This processing environment named CATENA was designed for uniform, automatic general purpose processing of huge amounts of optical satellite data of similar type. In this paper we present the concept of the processing system, the framework and the decomposition of processing requirements to processing modules and processing chains. We give some examples for already implemented general purpose or project specific processing chains and an analysis of performance and quality of the results.

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2012

Tree height is a fundamental parameter for describing the forest situation and changes. The lates... more Tree height is a fundamental parameter for describing the forest situation and changes. The latest development of automatic Digital Surface Model (DSM) generation techniques allows new approaches of forest change detection from satellite stereo imagery. This paper shows how DSMs can support the change detection in forest area. A novel region based forest change detection method is proposed using single-channel CARTOSAT-1 stereo imagery. In the first step, DSMs from two dates are generated based on automatic matching technology. After co-registration and normalising by using LiDAR data, the mean-shift segmentation is applied to the original pan images, and the images of both dates are classified to forest and non-forest areas by analysing their histograms and height differences. In the second step, a rough forest change detection map is generated based on the comparison of the two forest map. Then the GLCM texture from the nDSM and the Cartosat-1 images of the resulting regions are analyzed and compared, the real changes are extracted by SVM based classification.