Tools for Disaster Management and Infrastructure Mapping Projects Dr. Jens Kremer studied physics in the Univ. of Siegen (1990-95) PhD at Siegen Univ. about cosmic ray physics in 1999 since 1999 at IGI working on GPS/IMU integration since 2002 Manager R&D at IGI ABSTRACT Since 1982 IGI has specialized in the development of precise aircraft guidance and sensor management systems for aerial survey flight missions. These developments did result in the CCNS, Computer Controlled Navigation System, whose 4th generation is in world-wide operations with more than 200 companies. In 1996 IGI introduced AEROcontrol, a GPS/IMU(DTG) based system for the determination of the exterior orientation parameters of a sensor. In 2000 AEROcontrol-IId was presented with a FOG-based IMU for highest accuracies needed for aerial survey operations. The CCNS/AEROcontrol provides interfaces to a large number of aerial sensors like all major analog aerial cameras and new digital sensors like the Vexcel ULTRACAM-D and the Intergraph DMC. Together with the tools for aircraft guidance, sensor management and precise positioning, IGI integrates airborne sensors like laser scanners and medium format digital cameras to reliable airborne sensor systems, specialized for different airborne applications. The LiteMapper, a series of affordable LIDAR Terrain Mapping systems for creating DTMs/DSMs with fixed-wing aircraft or helicopters, is optimized for infrastructure mapping (e.g. power line and pipeline surveys), high precision DTM generation in urban areas, forestry and agricultural applications and rapid response missions. The DigiCAM medium format airborne digital camera system can be operated together with the LiteMapper or in a camera-only configuration with one or more cameras for different spectral bands. The typical applications for the DigiCAM are infrastructure mapping, orthophoto generation and medium size area mapping projects. The tight integration with the AEROcontrol GPS/IMU system, the easy and reliable operation and the short processing times make the DigiCAM well suited for rapid response applications and disaster management. In this paper the system components are described, the typical applications are defined and results from different mission are shown. 1. INTRODUCTION Within the last five years, dramatic changes have taken place in the aerial survey business. Small scale aerial photography has been taken over more or less by satellites and medium scale aerial photography has been directed to larger scales, black and white is nearly replaced by color. GPS and GPS/IMU technology have set milestones for saving ground control and speeding up the photogrammetric processing. Digital cameras are taking over the leading role for large format metric aerial camera systems. These large format digital cameras are expensive. For that reason it may be worth thinking about, if, e.g. mid-format digital cameras, can take over a role on providing the information needed. Especially for technical projects as streets/highways/railways, power-lines and pipelines for example, there is no need for an expensive large format digital camera. Since more than 20 years, IGI has specialized in the development of precise aircraft guidance and sensor management systems for aerial survey flight missions, resulting in CCNS4, the Computer Controlled Navigation System. Since nearly 10 years IGI offers a GPS/IMU based system for the determination of the exterior orientation parameters of a sensor at a given instant. The resulting product AEROcontrol-IId fulfills the highest demands on accuracy needed. The development of CCNS and AEROcontrol together with years of experience in interfacing different types of sensors, build the IGI core competence in airborne sensor applications. IGI used this basis for a development of the LiteMapper systems, and a new professional mid-format digital camera, the DigiCAM-H. 2. THE DigiCAM MID-FORMAT AERIAL CAMERA SYSTEM The DigiCAM digital airborne camera system combines a modified professional digital camera with a graphical user interface for real-time preview capability together with the CCNS/AEROcontrol. The image data is stored on an external exchangeable image bank. The camera can switched from RBG to CIR mode with little effort. 2.1. DigiCAM-H Design The DigiCAM-H system is based on Hasselblad camera components with a modified IMACON 22 MPixel CCD backplane. It has 4080 x 5440 pixels at 9 µm pixel size. With the DigiCONTROL computer with the touch-screen user interface the operator can check quick-views and exposure histograms of the actually taken photos in real time and change all necessary settings of the different cameras. With one DigiCONTROL he can control several cameras at once. For pre-planned flight missions, the cameras are triggered by the CCNS4. The DigiCAM-H is prepared for operations together with the AEROcontrol system for the determination of the EO-parameters of all images taken. One AEROcontrol can be operated together with one, two or four DigiCAM-H cameras mounted in a pod. Cameras in RGB mode can be combined with cameras in CIR mode.  Figure 1: DigiCAM-H system For each DigiCAM-H operated, an Image Bank stores 850 images in 16 bit color and full resolution, multiple storage devices can be used during one flight mission. For that reason the storage space can be scaled up in steps of 850 images just by using additional Image Banks of 0.72 kg each. The camera can be operated together with several fix-focus, calibrated lenses with electronic shutter. Lenses with focal length between 35mm and 300mm are available. The modular design of the DigiCAM-H enables a change from RGB mode to color-infrared mode within minutes. If RGB and CIR images shall be taken at the same time, two DigiCAM systems may be operated within one camera-pod. If a high image repetition time is needed, up to four DigiCAMs can be operated in one pod installed in a standard camera mount. The DigiCAM system is compatible with all kind of commonly used sensor mounts. The DigiCAM-H has an image repetition time of less than 2.5 seconds. 2.2. Targeted Operations The operation of medium format airborne camera is specially useful for corridor mapping projects (like roads, power- and pipelines), small to mid sized aerial mapping projects including rapid response projects and in the combination of the cameras together with other aerial sensors like LIDAR. The advantages of a mid-format camera for corridor mapping are obvious: For a typical corridor project, only the feature in the middle of the corridor provides the wanted information. If a sensor with a very high number of pixels perpendicular to the flight direction collects information far outside the wanted area, this information only costs processing time and storage space without any benefit.  Figure 2: Modular design of the DigiCAM For small to mid sized projects with a tight time schedule, the very fast availability of the images and the operation of standard storage hardware and standard formats together with the possible operation of about all types of aircraft, including ultra-light aircraft, leads to a very cost effective operation. Differently from the large format digital camera systems, this mid-format camera works with exchangeable lenses. This means that the camera can operate even under difficult weather conditions under the cloud cover with a wide angle lens. On the other hand, lenses with a long focal length are available to create orthophotos with minimal distortions in urban areas. 3. THE LiteMapper LIDAR TERRAIN MAPPING SYSTEM The LiteMapper is a series of airborne laser scanners that are tightly integrated with the CCNS4 flight guidance system, with the AEROcontrol GPS/IMU system and with the DigiCAM medium format digital camera. The LiteMapper provides measurements with highest accuracy in a compact and lightweight design. The CCNS4 guides the pilot on pre-planned flight lines, operates the LIDAR and triggers the digital camera(s). As a result of this tight integration, a dedicated LIDAR operator is not mandatory. Nevertheless, the systems contain a touch screen display to get real time information about the status of the system, to change the system settings, and to operate the system in manual mode. 3.1. LiteMapper-5600 Design The laser scanner used in the LiteMapper-5600 LIDAR system is a RIEGL LMS-Q560. It is extended by LMcontrol and LMtools a control and management system for the collected laser data. A sensor control unit for up to 60 hours data logging together with a detached 8 inch TFT touch-screen for data registration, visualization and quality control during the airborne mission are part of the LiteMapper systems.  Figure 3: LiteMapper-5600 The Riegl LMS-Q560 inside the LiteMapper-5600 provides a unique feature: it gives access to detailed target parameters by digitizing the echo waveform of each laser measurement [Hug et al. 2004]. After flight the digitized waveforms can be analyzed subsequently off-line. This approach proves especially valuable when dealing with challenging tasks, such as canopy height investigation or highly reliable automated target classification. For agricultural application this feature opens a complete new field of possibilities. The LiteMappe-5600 utilizes the time-of-flight distance measurement principle with infrared light pulses and a rotating mirror scanning system, providing absolutely linear, unidirectional and parallel scan lines. The laser pulse waveform can be extracted with high resolution and precision and can be used for in-depth waveform analysis in post processing. The waveform digitizing principle is illustrated in figure 4:  Figure 4: Waveform digitizing principle - Echo signals resulting from different targets [Riegl 2005] In situation 1, the laser pulse hits the canopy first and creates three distinct echo pulses. A fraction of the laser pulse also hits the ground giving rise to another echo pulse. In situation 2, the laser beam is reflected from a flat surface at a small angle of incidence yielding an extended echo pulse width. In situation 3, the pulse is simply reflected by a flat surface at normal incidence resulting in a single echo pulse with a similar shape as of the outgoing laser pulse.  Table 1: Specifications of the LiteMapper-5600 3.2. Targeted Operations For the operation of the LiteMapper, excellent possibilities can be seen in the following fields of application:
+ power lines + pipelines + railroads + highways In forestry and agricultural applications, the digitized waveform information is valuable for deriving several vegetation parameters: not only the vegetation height is available but also the vertical canopy structure and density are accessible. The height of second, third, and lower levels of vegetation, and the height and density of ground vegetation can be measured. Calculation of timber volume, biomass and other important vegetation descriptors is thus facilitated and made more precise. 4. CONCLUSIONS Based on the CCNS4 guidance and management system an on the AEROcontrol GPS/IMU system, IGI has combined laser scanners and a medium format digital camera to an integrated airborne sensor system for special applications. The LiteMapper LIDAR system is optimized for corridor mapping with helicopter or fixed wing aircraft and for small to medium sized topographic mapping projects with highest accuracy requirements. The waveform digitizing LiteMapper-5600 opens new possibilities for forestry and agricultural applications. The DigiCAM-H digital camera system provides a specialized system for corridor mapping and a cost efficient solution for small and medium sized photogrammetry projects. The capability to switch from RGB to CIR and to change between lenses with different focal length makes the DigiCAM system a versatile tool for all kind of projects where a large format digital camera can not be used efficiently. 5. REFERENCES
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