In order to support maritime search and rescue activities, an affordable gated-viewing instrument has been developed within the TRAGVIS project. The instrument, which got the name TRAGVIS after the project’s name, has the purpose of vision enhancement during night-time missions under bad visibility conditions. TRAGVIS consists of a compact, eye-safe NIR (near-infrared) laser light source and a monochromatic 1.3 Mpixel camera and has a field of view similar to the one of common field glasses. The camera sensor was recently upgraded from the Onyx to the Bora rev.A sensor from Teledyne–e2v, and a thorough comparison will be shown between them. Several field tests were conducted on an out of service airport and in a maritime environment. The measured gray values of the instrument were calibrated to the reflectivity of the targets at different distances. Furthermore, the performance of the instrument has been studied under different visibility conditions. Therefore, several images of the same target were taken with the gated-viewing mode enabled and disabled. These measurements showed that even during the presence of a light fog with an extinction coefficient of 3.8 km−1, the measured contrast decreased by more than a factor of 3 when gated-viewing was disabled. Contrary to this, no significant decrease in the contrast could be identified using the gated-viewing feature of our instrument. In the maritime environment, field tests at a close harbor were performed for the identification of different maritime objects such as sailing boats, rubber boats and drones. Using several TRAGVIS images taken at monotone increasing gate distances, a simple method was applied to build three dimensional images of this maritime scenery.
A novel gated-viewing instrument is presented for vision enhancement in maritime search and rescue applications predominantly under limited visibility conditions at night. The compact device consists of a camera and an eye-safe NIR (near-infrared) illuminator and has a field of view of ≈7° x 6°, which is similar to field glasses. The detection range is 250 m for Lambertian reflectors, but is much larger if clothes with retro-reflectors are worn. A key challenge is the cost effectiveness of the instrument as potential users in the field of maritime search and rescue applications usually suffer from financial limitations. As a result, no image intensifier, but an off-the-shelf CMOS camera in accumulation mode with a reasonable quantum efficiency in the NIR region is used. The active illumination is based on a self-developed illuminator consisting of 7 pulsed vertical-cavity surface-emitting laser (VCSEL) arrays. The mean optical power is 7 W, the center wavelength is λ≈804 nm, and the light pulse width is ≈100 ns at a repetition rate of 345 kHz. Detailed simulations leading to the system design are presented together with respective characterization measurements of the camera and illuminator as well as first test measurements of the complete system.
This paper, “A compact very high resolution camera (VHRC) for Earth and planetary exploration using a large array (7k x 8k) CCD," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.
KEYWORDS: Sensors, RGB color model, Data modeling, Cameras, Imaging systems, 3D modeling, Systems modeling, Data acquisition, Data fusion, Data processing
New stereo push broom camera systems have been developed at German Aerospace Centre (DLR). The new small
multispectral systems (Multi Functional Camerahead - MFC, Advanced Multispectral Scanner - AMS) are light weight,
compact and display three or five RGB stereo lines of 8000, 10 000 or 14 000 pixels, which are used for stereo
processing and the generation of Digital Surface Models (DSM) and near True Orthoimage Mosaics (TOM).
Simultaneous acquisition of different types of MFC-cameras for infrared and RGB data has been successfully tested. All
spectral channels record the image data in full resolution, pan-sharpening is not necessary.
Analogue to the line scanner data an automatic processing chain for UltraCamD and UltraCamX exists.
The different systems have been flown for different types of applications; main fields of interest among others are
environmental applications (flooding simulations, monitoring tasks, classification) and 3D-modelling (e.g. city
mapping). From the DSM and TOM data Digital Terrain Models (DTM) and 3D city models are derived. Textures for
the facades are taken from oblique orthoimages, which are created from the same input data as the TOM and the DOM.
The resulting models are characterised by high geometric accuracy and the perfect fit of image data and DSM.
The DLR is permanently developing and testing a wide range of sensor types and imaging platforms for terrestrial and
space applications. The MFC-sensors have been flown in combination with laser systems and imaging spectrometers and
special data fusion products have been developed. These products include hyperspectral orthoimages and 3D hyperspectral data.
The international project "Geo-Archaeology in the Steppe - Reconstruction of Cultural Landscapes in the Orkhon valley,
Central Mongolia" was set up in July 2008. It is headed by the Department of Pre- and Protohistoric Archaeology of
Bonn University. The project aims at the study of prehistoric and historic settlement patterns, human impact on the
environment and the relation between towns and their hinterland in the Orkhon valley, Central Mongolia. The
multidisciplinary project is mainly sponsored for three years by the German Federal Ministry of Education and Research
(BMBF) and bridges archaeology, natural sciences and engineering (sponsorship code 01UA0801C). Archaeologists of
the Mongolian Academy of Sciences and of the Bonn University, geographers of Free University Berlin, geophysics of
the Institute for Photonic Technology Jena and the RWTH Aachen University, and geographers and engineers of the
German Aerospace Centre Berlin collaborate in the development of new technologies and their application in
archaeology1. On the basis of Russian aerial photographs from the 1970s, an initial evaluation regarding potential
archaeological sites was made. Due to the poor geometric and radiometric resolution of these photographs, identification
of archaeological sites in many cases remained preliminary, and detailed information on layout and size could not be
gained. The aim of the flight campaign in September 2008 was therefore the confirmation of these sites as well as their
high resolution survey. A 10 megapixel range finder camera was used for the recording of high resolution aerial
photography. This image data is suited for accurate determination and mapping of selected monuments. The airborne
camera was adapted and mounted on an electrically operated eight propeller small drone. Apart from high resolution
geo-referenced overview pictures, impressive panoramic images and very high resolution overlapping image data was
recorded for photogrammetric stereoscopic processing. Due to the overlap of 85% along and across the track each point
in the image data is recorded in at least four pictures. Although a smaller overlap might be sufficient for generating
digital surface models (DSM), this redundancy increases the reliability of the DSM generation. Within this
photogrammetric processing digital surface models and true ortho photo mosaics with a resolution up to 2,5 cm/pixel in
X, Y, Z are derived.
In the context of rapid expansion of many cities to enormous agglomerations with high population density and a worldwide
urbanization process serious impacts on environment in urban areas evolve. There is a high demand for the
development and application of efficient methods to analyze and monitor changes in urban areas, to support the planning
decisions in these regions and for security and risk assessment. Efficient, accurate and reliable extraction of buildings
and roof surfaces and their inventory in geographic information systems plays a major role in this context.
Previous analyses of digital airborne data sets show up that the inventory mapping and assessment of building changes is
only possible on the basis of multi-temporal data sets and digital surface models with high resolution. These analyses
confirm explicitly that both high heterogeneity and diversification of urban regions as well as the availability of data sets
from different camera systems increase the need for automated and transferable extraction methods.
In this context two data sets from different high resolution sensors are used for the development of transferable
extraction rule sets within the object-based classification method in Definiens Developer. The Multifunctional Camera
(MFC3) and the UltraCamD (UCD) data sets not only have diverse geometric but also different radiometric
characteristics. As a study area the centre of Berlin, Germany was selected.
Two approaches to generate comparable results from different data sources are tested. The first step deals with the
generation of statistical parameters and the normalization of the two data sets. The second step addresses the
development and adaptation of the rule set for a robust and universal segmentation and classification process.
KEYWORDS: Sensors, Imaging systems, Charge-coupled devices, Modulation transfer functions, Microsoft Foundation Class Library, RGB color model, CCD image sensors, Remote sensing, Control systems, Satellites
The department of Optical Information Systems (OS) at the Institute of Robotics and Mechatronics of the German Aerospace
Center (DLR) has more than 25 years experience with high-resolution imaging technology. The technology
changes in the development of detectors, as well as the significant change of the manufacturing accuracy in combination
with the engineering research define the next generation of spaceborne sensor systems focusing on Earth observation and
remote sensing. The combination of large TDI lines, intelligent synchronization control, fast-readable sensors and new
focal-plane concepts open the door to new remote-sensing instruments. This class of instruments is feasible for high-resolution
sensor systems regarding geometry and radiometry and their data products like 3D virtual reality. Systemic
approaches are essential for such designs of complex sensor systems for dedicated tasks. The system theory of the instrument
inside a simulated environment is the beginning of the optimization process for the optical, mechanical and
electrical designs. Single modules and the entire system have to be calibrated and verified. Suitable procedures must be
defined on component, module and system level for the assembly test and verification process. This kind of development
strategy allows the hardware-in-the-loop design. The paper gives an overview about the current activities at DLR in the
field of innovative sensor systems for photogrammetric and remote sensing purposes.
The multi-spectral, multi-line and muliti-stereo HRSC airborne pushbroom imager provides digital ortho-images and digital surface models with a position accuracy of 10 to 20cm. Since the first experiments carried out in 1997, coverage of more than 150 cities and large areas have been acquired and processed in Europe and the USA.The spatial resolution and ground coverage of the HRSC-A, HRSC-AX, HRSC-AXW models of the imager can be varied due to flight altitude during operational airborne flights to give images from 10cm to 100cm in terms of spatial resolution and from 1km to 10km swath width, depending on the particular model of the HRSC that is used for the flight.
The multi-sensor multi-resolution technique (MMT) was applied to fuse a multispectral image obtained by the multispectral scanner DAEDALUS-1268 with the resolution of 6 m and a hyperspectral image obtained by the imaging spectrometer DAIS-7915. The spatial resolution of the DAIS- 7915 image was additionally degraded to 24 m in order to simulate multi-sensor data fusion with a very different sensor resolution, as is typical for satellite sensors. Both sensors had been operated simultaneously on one aircraft. The MMT algorithm includes: (1) (unsupervised) classification of the multispectral image and mapping the classes with the high resolution of the multispectral scanner, (2) retrieval of the hyperspectral signatures of these classes from the hyperspectral image, and (3) generation of the merged image which combines the pixel size of the multispectral scanner and the spectral bands of the imaging spectrometer. Additional low-pass correction of the merged image allowed us to increase significantly its accuracy. The minimal pixel error of 6.9% was obtained when the classification was performed with 256 spectral classes.
The digital airborne imaging spectrometer DAIS 7915 is a new hyperspectral scanner developed for scientific and commercial applications. The design of the sensor makes a dedicated preprocessing necessary, prior to any data evaluation. Therefore, a facility is being developed at DLR to fulfill the needs of operational preprocessing. Besides that this facility is used for continuous quality control to support the hardware team in improving the performance of the instrument. The implementation of the software and the algorithms currently used are presented in this paper.
The European Community and DLR are funding a 79-channel airborne imaging spectrometer (DAIS-7915) to be used for remote sensing applications such as environmental monitoring of land and marine ecosystems, vegetation stress research, agriculture and forestry resource mapping, geological mapping, mineral exploration and supply of data for geographic information systems. The DAIS sensor covers the spectral range from the visible to thermal infrared wavelengths at variable spatial resolutions from 2 - 30 m. Therefore, DAIS can also be used for the investigation of specifications for future airborne and spaceborne optical instruments for specific applications.
In May/June 1989 the German Aerospace Research Establishment (DLR) Institute for Optoelectronics was involved in the first European Imaging Spectroscopy Airborne Campaign (EISAC). Test sites in various countries of the European Community were flown with the GER-Il Scanner. In the presented study the preprocessed and atmospherically corrected data was used for a spectral analysis of an old vegetation covered waste deposit. 2. THE GER-Il Scanner The GER-lI Scanner (Geophysical Environment Corp. ) is a 63 channel imaging spectrometer with three seperate line arrays of detectors which view the ground through the same aperture via a rotating mirror. It contains 31 channels in the visible I near infrared (VIS/NIR) wavelength region (470 nm - 840 nm sampling interval 12. 3 nm) 4 channels between 1440 nm to 1900 nm (sampling interval 120 nm) and another 28 channels in the short wave infrared (SWIR) wavelength region (2000 nm - 2450 nm sampling interval 16. 3 nm). The IFOV was selected to be 3. 3 mrad which leads to a pixel size of 10 m at 3000 m flying altitude. The high spectral and spatial resolution make this scanner a useful tool for environmental studies. 3. DATA PROCESSING As a first evaluation step the GER-Scanner data was preprocessed including a roll- lag- and slope-correction1. Comparison of ground vegetation spectra measured with the IRIS-Mark IV spectroradiometer (GER-Corp. ) during the time of the overflight yielded
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