This paper discusses airborne light detection and ranging (LiDAR) point cloud filtering (a binary classification problem) from the machine learning point of view. We compared three supervised classifiers for point cloud filtering, namely, Adaptive Boosting, support vector machine, and random forest (RF). Nineteen features were generated from raw LiDAR point cloud based on height and other geometric information within a given neighborhood. The test datasets issued by the International Society for Photogrammetry and Remote Sensing (ISPRS) were used to evaluate the performance of the three filtering algorithms; RF showed the best results with an average total error of 5.50%. The paper also makes tentative exploration in the application of transfer learning theory to point cloud filtering, which has not been introduced into the LiDAR field to the authors’ knowledge. We performed filtering of three datasets from real projects carried out in China with RF models constructed by learning from the 15 ISPRS datasets and then transferred with little to no change of the parameters. Reliable results were achieved, especially in rural area (overall accuracy achieved 95.64%), indicating the feasibility of model transfer in the context of point cloud filtering for both easy automation and acceptable accuracy.
In order to raise the intelligent level and improve cooperative ability of grid. This paper proposes an agent oriented
middleware, which is applied to the traditional OGSA architecture to compose a new architecture named CIG
(Cooperative Intelligent Grid) and expounds the types of cooperative processing of remote sensing, the architecture of
CIG and how to implement the cooperation in the CIG environment.
KEYWORDS: Image processing, Remote sensing, Computing systems, Web services, Data processing, Sensing systems, Databases, Image compression, Internet, Local area networks
In this article, a remote sensing image processing system is established to carry out the significant scientific problem that
processing and distributing the mass earth-observed data quantitatively and intelligently with high efficiency under the
Condor Environment. This system includes the submitting of the long-distantly task, the Grid middleware in the mass image processing and the quick distribution of the remote-sensing images, etc. A conclusion can be gained from the application of this system based on Grid environment. It proves to be an effective way to solve the present problem of fast processing, quick distribution and sharing of the mass remote-sensing images.
Considering the deficiency of mapping model in traditional image registration, a new image registration method based on evolutionary modeling is proposed in this paper. Multi Expression Programming has been used as modeling tool to build mapping model. To avoid over fitting and improve actual effective, constraints of the mapping function's slope and curvature were added during modeling process. SAR image and optical image rectifying experiment is given in the last. The experiment result indicated that the evolutionary model has high precision for image registration. This method is fit for image registration.
Level set evolution theory is introduced to bridge or dam detection above river in order to improve performance in case
of very low contrast and faint targets feature in optical or radar imagery. Aiming at shortages like boundary leak, weak
robust to noises existing in classical level set methods, and sub- or over- segmentation, irregular boundary with gap
existing in traditional segmentation, an adaptive narrow band level set evolution model based on Chan-Vese model is
presented to excellently extract river regions from radar imagery with faint edge and unwelcome effects, while greatly
accelerate the curve evolution process. Furthermore, we propose a novel algorithm based on Narrow Band Level
Set(NBLS) for detecting and simultaneously distinguishing bridge and dam. The algorithm is efficient, avoiding the
disadvantages that medial-axis search methods are subjected to noises and are hard to process river branch with complex
shape. Finally, feature-weighted decision rule is adopted to combine the detection results from the two binary classifiers
form radar and optical imagery, in order to make use of complementary feature from different classifiers and to achieve
higher accuracy of targets detection than single classifier. Experimental results demonstrate that our scheme proposed in
the paper outperform some others, with the advantages of time-effectiveness and robust to noises.
The airborne hyperspectral remote sensing data, such as PHI, OMIS, has the virtues of high spatial and spectral resolution. Hence, from the view of target classification we can consider that it can provide the ability of discriminating targets more detailedly than other data. So it's important to extract thematic information and update database using this kind of data. Whereas, the hyperspectral data has abundant bands and high between-band correlation, the traditional classification methods such as maximum likelihood classifier (MLC) and spectral angle mapper (SAM) have performed poorly in thematic information extraction. For this reason, we present a new method for thematic information extraction with hyperspectral remote sensing data. We perform classification by means of combining the self-organizing map (SOM) neural network which is considered as full-pixel technique with linear spectral mixture analysis (LSMA) which is considered as mixed-pixel technique. The SOM neural network is improved from some aspects to classify the pure data and find the mixed data. And then the mixed data are unmixed and classified by LSMA. The result of experiment shows that we can have the better performance in thematic information extraction with PHI by this means.
This paper presents a method for ports detection based on the framework of feature level fusion. Bearing in mind the fact that parallel lines and rectangular corners are main features in most ports, and ports are large scale man-made objects, these features are firstly extracted from high-to-moderate resolution optical satellite imagery. Taking account for the balance of data acquisition and spatial resolution, SPOT panchromatic image is used for such feature extraction. Considering the whether conditions in coastal area, which is characterized by rainy and cloudy climate, Radarsat image with the similar spatial resolution as SPOT panchromatic is used to extract linear features along coastal line. Since ships and boats are typical objects that can be easily detected in radar image, these are considered to be supplemented features for ports detection. All extracted features are associated under the framework of feature level fusion. The whole procedure can be described as follows: the first step is preprocessing the input images, mainly histogram stretching to SPOT image for visual quality improvement and filtering to radar image for denoising speckles. Then registration between SPOT and Radarsat image is carried out. Since Radarsat image is used mainly for coastal line extraction and ship detection, rigorous geometric processing is omitted since little attention will be paid to land area. Common polynomial model is used for co-registration with Ground Control Points manually selected from both images. Due to feature level fusion method is adopted, registration accuracy is not as a key factor as in pixel level fusion. The next step will be linear features and rectangular corners detection both in optical and radar image. The detected linear features are then fitted by least mean-square-error algorithm. All the detected features are associated by simply weighted mean algorithm, with different weights to features from optical and radar images. An automatic ports detection system based on the abovementioned procedure is developed. Experiments show that most ports can be detected by our method.
This paper describes the use of semivariogram as a parameter for image comparison which is a commonly used method in content-based image retrieval. The authors first review various applications of spatial statistics to image and signal processing, and recent literature of image comparison, with the emphasis to global image structure description and distance-based image retrieval techniques. The difficulty arising in this field is the definition of image similarity. A new parameter based on semivariogram is putted forward by the authors. Bearing in mind that semivariogram is a parameter not only describes the global structure of a data set but also describes the local continuity of that data set, it is shown in the paper that semivariogram is suitable for global image comparison, and can be used to reveal local features of the image as well. Based on this property, a new index for image similarity is constructed and a practical program using it is developed. By applying the approach to a practical problem, the results show that this approach has the following merits: (a) high sensitivity to structure differences of an image. (b) low computational complexity, and (c) high robustness to lightening conditions.
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