Stefan Auer

Stefan Auer
German Aerospace Center (DLR) | DLR · Department of Photogrammetry and Image Analysis

Dr.-Ing.

About

79
Publications
38,692
Reads
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1,133
Citations
Citations since 2017
37 Research Items
830 Citations
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2017201820192020202120222023050100150
Introduction
Stefan Auer is a senior scientist and project manager at the Remote Sensing Technology Institute (IMF) at DLR, Oberpfaffenhofen, Germany. His main interest is in data fusion methods and image analysis. In his doctoral thesis at TU Munich, he developed RaySAR, a SAR simulator based on ray tracing techniques. The simulator (version 1.2 released on 2021-04-21) can be downloaded from GitHub (https://github.com/StefanJAuer/RaySAR/releases).
Additional affiliations
December 2014 - present
German Aerospace Center (DLR)
Position
  • Senior Researcher
April 2011 - December 2014
Technische Universität München
Position
  • Senior Researcher
December 2006 - March 2011
Technische Universität München
Position
  • Research Assistant

Publications

Publications (79)
Article
Full-text available
Buildings are the predominant objects that characterize the urban structure. For many cities, local governments establish building databases for administration as well as urban planning and monitoring. However, newly constructed buildings are often only included with a considerable time delay in the official digital cadastral maps due to processes...
Article
Ground-Based Synthetic Aperture Radar (GB-SAR) enables to monitor a scene in a distance up to a few km and with an accuracy of around one mm. It is mainly used for landslide monitoring but also used to monitor man-made structures such as bridges and dams. Due to the particular distance-dependent imaging concept and related geometric distortion effe...
Conference Paper
Highly accurate reference vehicle trajectories are required in the automotive domain e.\,g. for testing mobile GNSS devices. Common methods used to determine reference trajectories are based on the same working principles as the device under test and suffer from the same underlying error problems. In this paper, a new method to generate reference v...
Article
Full-text available
Highly accurate reference vehicle trajectories are required in the automotive domain e. g. for testing mobile GNSS devices. Common methods used to determine reference trajectories are based on the same working principles as the device under test and suffer from the same underlying error problems. In this paper, a new method to generate reference ve...
Article
Full-text available
Timely information on land use, vegetation coverage, and air and water quality, are crucial for monitoring and managing territories, especially for areas in which there is dynamic urban expansion. However, getting accessible, accurate, and reliable information is not an easy task, since the significant increase in remote sensing data volume poses c...
Article
Aufbauend auf einer vorangegangenen Studie über den Einsatz von Künstlicher Intelligenz (KI) zur Detektion von Gebäudeveränderungen im amtlichen Liegenschaftskataster, wird in diesem Beitrag die Transformation von der Projektphase in einen Produktivbetrieb vorgestellt, es werden verschiedene KI-Architekturen angesprochen, miteinander verglichen und...
Conference Paper
Over the last 30-40 years, archaeology has moved from being focused on excavation of individual sites, to analyse broader patterns in archaeological sites at regional level. This branch is called “landscape archaeology”, and looks at the interaction among ancient human communities. Remote sensing played a key role in this area, but the use of space...
Article
Full-text available
To allow for a robust and automatic exploitation of Sentinel-2 data, Analysis Ready Data (ARD) products are requested by most users. The processors of ARD products take care of the common burdens necessary for most applications, that include precise orthorectification, cloud detection and atmospheric correction steps, as well as the generation of p...
Article
Full-text available
Undocumented building constructions are buildings or stories that were built years ago,but are missing in the official digital cadastral maps (DFK). The detection of undocumented buildingconstructions is essential to urban planning and monitoring. The state of Bavaria, Germany, uses twosemi-automatic detection methods for this task that suffer from...
Conference Paper
This paper describes the contribution of the DLR team ranking 2nd in Track 2 of the 2020 IEEE GRSS Data Fusion Contest. The semantic classification of multimodal earth observation data proposed is based on the refinement of low resolution MODIS labels, using as auxiliary training data higher resolution labels available for a validation data set. Th...
Conference Paper
This paper describes the contribution of the DLR team ranking 3rd in Track 1 of the 2020 IEEE GRSS Data Fusion Contest, with results ranking 2nd in Track 2 of the same contest are reported in a companion paper. The classifications are based on refinements of low-resolution MODIS labeling on available higher resolution Sentinel-1 and Sentinel-2 data...
Article
Full-text available
Undocumented buildings are buildings which were built years ago, but were never recorded in official digital cadastral maps. Detection of undocumented buildings is of great importance for urban planning and monitoring. The state of Bavaria, Germany, pursues this task based on high resolution optical data and digital surface models, using semi-autom...
Preprint
Generative Adversarial Networks (GANs) have been employed with certain success for image translation tasks between optical and real-valued SAR intensity imagery. Applications include aiding interpretability of SAR scenes with their optical counterparts by artificial patch generation and automatic SAR-optical scene matching. The synthesis of artific...
Conference Paper
To allow a robust and automatic exploitation of Sentinel-2 data, Analysis Ready Data (ARD) products are requested by most users. The ARD products take care of the common burdens necessary for most applications, that include the cloud detection and atmospheric correction steps, as well as the generation of periodic syntheses of cloud free surface re...
Conference Paper
Generative Adversarial Networks (GANs) have been employed with certain success for image translation tasks between optical and real-valued SAR intensity imagery. Applications include aiding interpretability of SAR scenes with their optical counterparts by artificial patch generation and automatic SAR-optical scene matching. The synthesis of artific...
Article
Full-text available
Zusammenfassung: Es wird ein neuartiger Ansatz vorgestellt, der auf einer Erkennung von Gebäuden und Gebäudeveränderungen aus hochaufgelösten Luftbildern anhand von Künstlicher Intelligenz (KI) beruht. Die zum Trainieren des KI-Systems notwendigen Datenbestände sind die Gebäudeumrisse aus der amtlichen Digitalen Flurkarte (DFK) und das lagerichtige...
Conference Paper
Undocumented buildings are buildings which were built years ago, but were never recorded in official digital cadastral maps.Detection of undocumented buildings is of great importance for urban planning and monitoring. The state of Bavaria, Germany,pursues this task based on high resolution optical data and digital surface models, using semi-automat...
Article
Full-text available
Due to its all time capability, synthetic aperture radar (SAR) remote sensing plays an important role in Earth observation. The ability to interpret the data is limited, even for experts, as the human eye is not familiar to the impact of distance-dependent imaging, signal intensities detected in the radar spectrum as well as image characteristics r...
Conference Paper
Full-text available
In contrast to the fields of computer vision and photogrammetry, multiple view geometry has not been extensively exploited in the remote sensing domain so far. Therefore, an empirical study is conducted based on multi view Pléiades data that depicts a scene from multiple orbits and multiple incidence angles. First, an accuracy analysis of the 2D an...
Conference Paper
Full-text available
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) ar...
Article
Full-text available
DLRAD – a new vision and mapping benchmark dataset for autonomous driving is under development for the validation of intelligent driving algorithms. Stationary, mobile, and airborne sensors monitored simultaneously the environment around a reference vehicle, which was driving on urban, suburb and rural roads in and around the city of Braunschweig/G...
Conference Paper
Operations in a military naval context require a detailed planning and information gathering. For this purpose, remote sensing is a useful technique without in-situ survey. A collaboration of Fraunhofer IOSB (Institute of Optronics, System Technologies and Image Exploitation), DLR (German Aerospace Center), and Bundeswehr Geoinformation Centre ZGeo...
Conference Paper
The fusion of heterogeneous image data, in particular optical images and synthetic aperture radar (SAR) images, is highly worthwhile in the context of remote sensing tasks as it allows to exploit complementary information – such as spectral and distance measurements or different observation perspectives – of the two data sources while diminishing t...
Article
Full-text available
In this paper, we present a work-flow to investigate the joint visibility between very-high-resolution SAR and optical images of urban scenes. For this task, we extend the simulation framework SimGeoI to enable a simulation of individual pixels rather than complete images. Using the extended SimGeoI simulator, we carry out a case study using a Terr...
Article
Full-text available
Tasks such as the monitoring of natural disasters or the detection of change highly benefit from complementary information about an area or a specific object of interest. The required information is provided by fusing high accurate co-registered and geo-referenced datasets. Aligned high resolution optical and synthetic aperture radar (SAR) data add...
Technical Report
This document provides the theoretical basis that hides behind the modules of MAJA processor. MAJA stands from MACCS-ATCOR Joint Algorithm, where MACCS was a Multi-Temporal Atmospheric Correction and Cloud Screening software, developed by CNES and CESBIO, and ATCOR is an Atmospheric Correction software developed by DLR. MAJA is based on MACCS archi...
Article
The successful alignment of optical and SAR satellite data requires that we account for the effects of sensor-specific geometric distortion, which is a consequence of the different imaging concepts of the sensors. This paper introduces SimGeoI, a simulation framework for the object-related interpretation of optical and SAR images, as a solution to...
Conference Paper
This paper presents the basics and functionality of SimGeoI, a simulation-based framework for the automated interpretation and alignment of optical and SAR remote sensing data. SimGeoI has been developed in order to relate optical and SAR data based on geometric information about objects represented by digital surface models. Thus, an analysis inde...
Conference Paper
Full-text available
A major research area in remote sensing is the problem of multi-sensor data fusion. Especially the combination of images acquired by different sensor types, e.g. active and passive, is a difficult task. Over the last years deep learning methods have proven their high potential for remote sensing applications. In this paper we will show how a deep l...
Article
Full-text available
Improving the geo-localization of optical satellite images is an important pre-processing step for many remote sensing tasks like scene monitoring over time or the scene analysis after sudden events. These tasks often require the fusion of geo-referenced and precisely co-registered multi-sensor data. Images captured by high resolution synthetic ape...
Article
Full-text available
The assignment of phase center positions (in 2D or 3D) derived from SAR data to physical object is challenging for many man-made structures such as buildings or bridges. In contrast, light poles and traffic signs are promising targets for tasks based on 3-D geolocation as they often show a prominent and spatially isolated appearance. For a detailed...
Article
Full-text available
GeoRaySAR, an automated SAR simulator developed at DLR, identifies buildings in high resolution SAR data by utilizing geometric knowledge extracted from digital surface models (DSMs). Hitherto, the simulator has utilized DSMs generated from LiDAR data from airborne sensors with pre-filtered vegetation. Discarding the need for pre-optimized model in...
Conference Paper
Full-text available
MACCS is a Multi-Mission Atmospheric Correction and Cloud Screening software. This tool has been developed by CNES. It is based on a multi-temporal algorithm that makes an optimized use of image time series to characterize the atmosphere and detect clouds. We have generated level-2 Sentinel-2 products on various targets over Europe but also over de...
Article
This paper presents two change-detection strategies based on the fusion of scene knowledge and two high-resolution synthetic aperture radar (SAR) images (pre-event, postevent) with focus on individual buildings and facades. Avoiding the dependence of the signal incidence angle, the methods increase the flexibility with respect to near-real-time SAR...
Conference Paper
RaySAR, a 3D SAR simulator, has been made accessible to the SAR community in January 2016. It helps to understand and analyze reflection effects of radar signals at 3D object models. For instance, the nature of persistent scatterers or " ghost " scatterers at man-made structures or basic reflection effects at canonical shapes can be interpreted in...
Conference Paper
The paper describes the direct retrieval of global coordinates of persistent scatterers (PS) including their secular displacement by plate tectonics from Synthetic Aperture Radar (SAR). For this purpose we combine stereo SAR methods, least squares parameter estimation, and geodetic observation corrections. The procedure is based on our previous res...
Conference Paper
This paper presents preliminary results of a workflow for generating facade reference data as a basis for evaluating the localization capability of 3D SAR algorithms (tomographic or radargrammetric). In this context, the required facade model is provided based on photogrammetric reconstruction and terrestrial surveys with cm-accuracy. The SAR simul...
Article
Full-text available
Various applications, like for instance algorithm design, mission planning, geo-referencing, change detection, Automatic Target Recognition (ATR) or SAR data analysis, rely on simulated synthetic aperture radar (SAR) images. However, there are different SAR simulation techniques with different advantages and disadvantages. Depending on the needs of...
Conference Paper
Motivated by the distinct appearance of facades in high resolution SAR images with respect to signal incidence angles and polarizations, this paper introduces a way to fuse SAR imagery and 3D GIS (geoinformation system) data (format: CityGML) based on SAR simulation methods. To this end, the known building geometry is used to simulate the extent of...
Conference Paper
The combination of geodetic principles for correcting radio signals with spaceborne Synthetic Aperture Radar (SAR) has led to a new type of accurate radar observations. This approach is comparable to satellite altimetry or Global Navigation Satellite Systems (GNSS), where errors in the signal time-of-flight caused by the Earth’s atmosphere and the...
Conference Paper
SAR-EDU is a German initative to generate training material for Universities to facilitate teaching the prinicples of SAR and the prominent applications. No full text of this presentation is available Please note that the whole content of SAREDU.dlr.de was moved to EO-College.org which will evolve into the new E-Learning Portal for Earth Observati...
Conference Paper
Full-text available
This paper discusses the potentials and challenges of the recognition of individual tree patterns in image data acquired by decimeter-resolution airborne synthetic aperture radar (SAR) systems working in the millimeterwave domain. Due to the different characteristics of conventional optical imagery and side-looking SAR imagery, sophisticated proces...
Article
Thanks to the high resolution of modern SAR satellites many persistent scatterers (PS) appear at single buildings. Approximately half of them represent building facades. These groups of points often show regular patterns in SAR images that can be related to repeating structure elements on the facades. Hence, individual buildings can now be monitore...
Conference Paper
Full-text available
This paper presents an approach for single tree detection in millimeterwave SAR intensity data. Due to the low canopy penetration of millimeterwave SAR trees are imaged with a high level of detail. Nevertheless, the appearance of trees in the image is manifold and rather nondescript which imposes some challenges to automatic detection schemes. Star...
Conference Paper
Change detection of two SAR images captured with different incidence angles is a difficult task but may be important in urgent situations like earthquakes. This paper presents a simulation based algorithm to detect negative changes of buildings in two high resolution SAR images captured with different incidence angles. The analysis is supported by...
Article
Full-text available
The 2012 Data Fusion Contest organized by the Data Fusion Technical Committee (DFTC) of the IEEE Geoscience and Remote Sensing Society (GRSS) aimed at investigating the potential use of very high spatial resolution (VHR) multi-modal/multi-temporal image fusion. Three different types of data sets, including spaceborne multi-spectral, spaceborne synt...
Conference Paper
Thanks to the high resolution of modern SAR satellites many persistent scatterers (PS) appear at single buildings, approximately half of them representing building facades. These groups of points often show regular patterns in the SAR images that can be related to repeating structure elements on the facades. Hence, individual buildings can now be m...
Conference Paper
Full-text available
Since the 1970s, radar remote sensing techniques have evolved rapidly and are increasingly employed in all fields of earth sciences. Applications are manifold and still expanding due to the continuous development of new instruments and missions as well as the availability of very high-quality data. The trend worldwide is towards operational employm...
Article
Full-text available
Most of the existing SAR simulators provide simulated images only for visual interpretation. This paper presents a new approach for supporting the automatic interpretation of very high resolution SAR images in complex urban scenarios. To this end, an automatic processing chain for generating and geocoding of simulated images has been developed, bas...
Conference Paper
This paper presents a new algorithm for recognizing patterns pertinent to the layover of façades in very high resolution SAR images, serving the increasing demand for monitoring individual buildings. The grouping of signatures is based on the combination of a weighted Hough transform and the analysis of spectrum peaks. First results of pattern extr...
Conference Paper
As a SAR image is often the only available data in crisis situations, e.g. after an earthquake, a change analysis of the SAR image with previously acquired data may enable a fast analysis of the damage caused by the disas-ter. This paper presents a method for change analysis of the simulated appearance of a digital surface model (DSM) and a SAR ima...
Conference Paper
Full-text available
As a SAR image is often the only available data in crisis situations, e.g. after an earthquake, a change analysis of the SAR image with previously acquired data may enable a fast analysis of the damage caused by the disas-ter. This paper presents a method for change analysis of the simulated appearance of a digital surface model (DSM) and a SAR ima...
Conference Paper
With the enhancing availability and variety of space borne Synthetic Aperture Radar (SAR) data and a growing number of analysis algorithms the need for a vital user community is increasing. Therefore the German Aerospace Center (DLR) together with the Friedrich-Schiller-University Jena (FSU) and the Technical University Munich (TUM) launched the ed...
Conference Paper
When exploiting very high resolution SAR data stacks, the persistent scatterer interferometry algorithm may mistakenly localize scatterers below the ground level. This paper supports this assumption by a case study using the 3D SAR simulator RaySAR. For a specific urban scene, signal reflections between two adjacent buildings lead to the occurrence...
Conference Paper
Full-text available
Because of the all-weather and all-time data acquisition capability, high resolution space borne synthetic aperture radar (SAR) plays an important role in remote sensing applications like earth mapping. However, the visual interpretation of SAR images is usually difficult, especially for urban areas. This paper shows a method for visual interpretin...
Conference Paper
Using long-time coherent scatterers in SAR data, called Persistent Scatterers (PSs), the deformation signal of objects can be measured from space. However, the nature of the corresponding image signatures is not known in detail. Methods focused on the simulation of highly detailed object models help to understand the origin of PSs. In this paper, s...
Thesis
Full-text available
Due to the high spatial resolution of up to 1 m, very high resolution spaceborne SAR sensors such as TerraSAR-X/TanDEM-X or COSMO-SkyMed enable the monitoring of single objects on the earth surface. However, the interpretation of the appearance of objects on SAR images is difficult due to distortion effects like foreshortening or layover. So far, t...
Article
This paper confirms the need for detailed 3D models for the simulation of high-resolution SAR images in order to support Persistent Scatterer Interferometry (PSI) focused on single urban objects. Using a building model enhanced by facade grammar, multiple reflections at building facades are analyzed using ray tracing techniques and scatterers are l...
Conference Paper
Simulation of artificial reflectivity maps supports the interpretation of high resolution SAR images in the azimuth-range plane. Nonetheless, simulation in 3D is mandatory in order to localize and identify salient point scatterers which, for instance, are analyzed for detecting deformation signals by Persistent Scatterer Interferometry. This paper...
Article
In TerraSAR-X spotlight data features of man-made objects in urban areas become visible. In a case study, this paper presents results of a precision and geometrical accuracy investigation of extracted double-bounce lines in SAR images. Two TerraSAR-X (TSX) acquisitions of a complex urban scene are compared to simulated SAR images. Using a new line...
Article
In this paper, a simulation concept is presented for creating synthetic aperture radar (SAR) reflectivity maps based on ray tracing. Three-dimensional models of man-made objects are illuminated by a virtual SAR sensor whose signal is approximated by rays sent through the model space. To this end, open-source software tools are adapted and extended...
Conference Paper
The side-looking geometry of SAR sensors hampers the interpretation of SAR images of urban areas. Simulation tools for illuminating 3D models of man-made objects by means of a virtual sensor support the interpretation of scattering effects by providing artificial images in the azimuth-range plane. In this paper, a simulation approach is presented w...
Article
Modern space borne SAR sensors like TerraSAR-X and COSMO-SkyMed are capable of acquiring images with a geometric ground resolution of one meter. Airborne sensors achieve even higher ground resolution. In such very high resolution SAR imagery single objects like houses and bridges become visible. However, effects due to the side-looking slant range...
Conference Paper
Full-text available
An inherent drawback of SAR imaging of complex 3D structures is the potential layover of more than one scatterer in one resolution cell. Such scatterers can be separated by tomographic processing of multiple SAR images acquired with different across-track baselines. Simulation tools may further support interpretation of such layover effects appeari...
Conference Paper
Full-text available
Zusammenfassung: Aufnahmen aktueller SAR-Sensoren ermöglichen aufgrund sehr hoher geometrischer Auflösung die Analyse urbaner Gebiete. Die Szenenanalyse wird jedoch durch SAR-spezifische Effekte wie Foreshortening, Layover und Shadowing erschwert. Die Interpretation der SAR-Bilder kann durch die kombinierte Auswertung mit optischen Luftbildern erle...
Conference Paper
Full-text available
This paper presents an approach for using backward ray tracing for simulating radar reflectivity maps. After explaining the simulation concept which consists of three parts - modeling, sampling and image generation - two applications are presented for showing the performance of the simulator. At first reflection contributions like single or multipl...
Conference Paper
This paper deals with the analysis of persistent scatterers (PS) in urban areas. We approach the challenge of understanding and exploiting the potential of the new high resolution spaceborne radar data from two sides: a model-driven point of view, i.e., using a forward simulation based on a ray tracer that has been modified for SAR imaging, and a d...
Article
Full-text available
Modern industrial production involves complex and time-critical process chains which demand a sophisticated supply chain management and logistics as well as safe and reliable transport systems. Inside a vast factory individual parts (e.g. engines) cover large distances by using specific transport lines, e.g. electric monorail suspension conveyors....
Conference Paper
This paper introduces a modularized tool for the processing of LIDAR data based on the analysis of neighbor relationships between LIDAR points with the goal to extract planes, lines, and points in 3D. The tool's functionalities will be exemplified by the application of reconstructing building roofs. Detecting buildings within digital surface models...

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