With the development of miniaturization of drones and spectral cameras, unmanned Airborne spectral imaging technology has become possible. How to reduce the volume and quality of multi-spectral cameras while improving data acquisition performance and efficiency, making them more widely used in low-altitude remote sensing has become the focus of current research. In this paper, we develop multi-spectral camera development and data preprocessing technology based on array filter splitting. In the development of camera, we replace the optical path splitting, filter wheel and multi-lens splitting by filter splitting, which solves the multi-spectral camera. At the same time of data quality, two array filters were designed because the imaging method limited the camera to the ideal volume and quality. The improved filter greatly reduced the spectral aliasing between the bands. In the data processing, an improved SURF stitching algorithm based on sparse matrix beam adjustment is proposed to improve the speed of image stitching. The research results show that this paper successfully developed a multi-spectral camera with simple optical path, high acquisition efficiency, stable performance, small mass and low cost, and successfully combined with small and small drones for data acquisition and processing. The academic value and production value, the data acquisition achieves the generation of multi-spectral image of the whole scene, and the band stitching precision is 0.12 pixels, which has high application value.
Axis-shift multi-camera has been gradually applied in the aerial photogrammetry because of its advantages on structure design. In this paper, the basic axis-shift theory is analyzed, and an improved calibration method is described. A prototype system, including two axis-shift cameras, is developed to validate the feasibility and correctness of the proposed method. With the help of a high-precision indoor control field, the parameters of single camera and the relative orientation parameters of the dual camera system are calculated respectively. Experiment result indicates that this calibration method is suitable for the axis-shift multi camera system.
The application of high-resolution airborne images becomes more and more extensive. However because of the complexity of atmospheric environment, airborne remote sensing imaging process is easily affected by cloud and mist, which results in airborne image blurred or loss of information. So it is a necessary task to remove effects of cloud to get clearer images before the next application such as image registration. This paper proposes a new method of removing thin cloud cover from single airborne image. This method applies scale space transform to get scale space sequence images. Then we use difference between different levels to extract cloud area. Next, we use gray classification which represents cloud effect degree in the highest level of cloud area. Finally, we use the original image filtered by Laplacian to subtract the last step result. Compared with other thin cloud cover removal methods which include the homomorphic filtering method, wavelet transform method and mathematical morphology by visual evaluation and statistical analysis, the method proposed by this paper proves to be the most efficient way in the processing of thin cloud cover of airborne image.
According to the characteristic of multi-digital cameras system, the paper presents the concept of System's Interior
Orientation Parameters (SIOP) and verifies that the SIOP acquired from calibration in the inside field can effectively
improve the accuracy and efficiency of data processing of multi-digital cameras system. Importantly, the paper builds a
solution model of SIOP and verifies the feasibility of this solution model by experiment. Above all, the major research in
the paper gives an answer to the question that how to calibrate the multi-digital cameras system efficiently and
accurately.
Several composite camera systems were made for wide coverage by using 3 or 4 oblique cameras. A virtual projecting
center and image was used for geometrical correction and mosaic with different projecting angles and different spatial
resolutions caused by oblique cameras. An imaging method based axis-shift theory is proposed to acquire wide coverage
images by several upright cameras. Four upright camera lenses have the same wide angle of view. The optic axis of lens
is not on the center of CCD, and each CCD in each camera covers only one part of the whole focus plane. Oblique
deformation caused by oblique camera would be avoided by this axis-shift imaging method. The principle and
parameters are given and discussed. A prototype camera system is constructed by common DLSR (digital single lens
reflex) cameras. The angle of view could exceed 80 degrees along the flight direction when the focal length is 24mm,
and the ratio of base line to height could exceed 0.7 when longitudinal overlap is 60%. Some original and mosaic images
captured by this prototype system in some ground and airborne experiments are given at last. Experimental results of
image test show that the upright imaging method can effectively avoid the oblique deformation and meet the geometrical
precision of image mosaic.
Remote sensing, especially airborne remote sensing, can be an invaluable technique for quick response to natural disasters. Timely acquired images by airborne remote sensing can provide very important information for the headquarters and decision makers to be aware of the disaster situation, and make effective relief arrangements. The image acquisition and processing of Multi-mode Airborne Digital Camera System (MADC) and its application in
Wenchuan earthquake disaster monitoring are presented in this paper.
MADC system is a novel airborne digital camera developed by Institute of Remote Sensing Applications, Chinese Academy of Sciences. This camera system can acquire high quality images in three modes, namely wide field, multi-spectral (hyper-spectral) and stereo conformation. The basic components and technical parameters of MADC are also presented in this paper.
MADC system played a very important role in the disaster monitoring of Wenchuan earthquake. In particular, the map of dammed lakes in Jianjiang river area was produced and provided to the front line headquarters. Analytical methods and information extraction techniques of MADC are introduced. Some typical analytical and imaging results are given too.
Suggestions for the design and configuration of the airborne sensors are discussed at the end of this paper.
Crop leaf water content can be a valuable biochemical parameter to diagnose crop water stress. The leaf water content
characterizes some spectral absorption features in NIR band. Some researchers have proved that it was feasible to
retrieve leaf water content utilizing those spectral absorption features. Measured leaf water content data of several sorts
of winter wheat and the corresponding reflectance, CHRIS images were collected. Even 974 nm, 1160 nm and 1440 nm
were absorption feature bands of foliar water, the predicted accuracies of leaf water content only using these bands were
not satisfying. Four popular indices of vegetation water content including NDWI, SR, WI and REP were used to build
the predict model and evaluated though relativity analysis. SR and REP opposed the stronger predicted accuracy of leaf
water content than other spectral indices. Limited to the band position setting and band spectral function of CHRIS, SR
and REP were modified fit to the band setting of CHRIS. The predicted model based on ground reflectance were made to
adaptable to the band spectral function of CHRIS sensors, and the results showed that wide band spectral function indeed
caused a lower accuracy of crop water content than narrow band spectral function.
Multi-mode Airborne Digital Camera System (MADC) was developed by Institute of Remote Sensing Applications and
Shanghai Institute of Technical Physics in 2006. The system is enhancing and optimizing further now. It could realize
three modes of wide field, multispectral, and stereophotography based on three 4K*4K CCD digital cameras in the
course of taking aerial photography. Several finished aerial experiments have already demonstrated that the system has
good performance for aerial photography; both the software and the hardware of MADC could work stably and reliably.
Multispectral mode is a popular imaging way in airborne remote sensing. It can obtain multi-bands remote sensing
images by using several digital cameras synchronously. The multispectral images can make use for various remote
sensing applications, such as environment monitoring, resource researching, military use, and so on. In some special
conditions, images which get by using less than 10nm bandwidth narrowband filters can be treat as hyperspectral images;
so that we can consider the multispectral imaging way is a new approach for hyperspectral bands selection and data
acquisition. In this paper, we will mainly discuss the following questions for the multispectral mode of MADC: the
design principle, the basic arithmetic or model, the installation mode, the corresponding aerial experiments, the
application fields and the ways of multitspectral images processing. At the same time, some important accessorial
devices of MADC are also introduced. The point and conclusion will be received based on the practice installation,
operation, ground and aerial experiments.
KEYWORDS: Image quality, Photography, Imaging systems, Image processing, Camera shutters, Digital cameras, Cameras, Signal to noise ratio, Remote sensing, Servomechanisms
Multi-mode Airborne Digital Camera System (MADC) was developed by Institute of Remote Sensing Applications and
Shanghai Institute of Technical Physics in 2006. Several finished aerial experiments have already demonstrated that the
system has good performance for aerial photography. But the image smear which leads by position change and forward
motion of aircraft has adverse effect on the images quality. So finding an effective way to realize image smear
compensation is a key technique to improve and develop unceasingly for MADC system. We have designed the external
image smear compensation module and written the special image processing soft to compensate the image smear. Some
experiments and simulations in laboratory or on the ground have shown that the two ways for image smear compensation
are both useful for getting better aerial remote sensing images by MADC system. Aerial experiments will be
implemented to verify these methods further.
For the large need of the high resolving power spatial data, a multi-mode airborne digital camera system (MADC) is researched and integrated which has the characters of wide field, multi-spectrum and stereo imaging. This paper introduces the constitution and the technical specifications. MADC can be combined with Position and Orientation System (POS) to get the orientation data of every image, thus, the geometric correction of the image can be done in case of that there are little or no ground control points (GCP), which saves the heavily late works. Many aerial experiments have been executed, and a mass of high quality images were captured. At last, the perspective of MADC's applications in the remote sensing fields is analyzed.
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