Chao Chen

Extraction of bridges over water from high-resolution optical remote-sensing images based on mathematical morphology

Bridges over water are typical man-made structures on the land’s surface. An accurate extraction of such bridges from high-resolution optical remote-sensing images plays an important role in civil, commercial, and military applications. Considering the complex features of ground objects within high-resolution optical remote-sensing images and the inefficiency of previous methods of bridge extraction with random bridge orientation, direction-augmented linear structuring elements were constructed and applied in this study by using mathematical morphology to identify and extract bridges over water with different orientations. First, the image pre-processing is performed to facilitate the object extraction. Then by using the histogram-based threshold segmentation method, water bodies such as rivers are extracted and described as a binary image. Based on water bodies, the appropriate direction-augmented linear structuring element is then selected. Together with mathematical morphology operations, such as dilation and erosion, potential bridges are extracted by overlay analysis. Assisted by prior knowledge of bridges, false bridges are screened out and post-processing is finally performed to refine the extracted true bridges. This approach was validated with experiments in Shanghai and Beijing, China. The results show that the direction-augmented linear structuring elements are of high precision and have the capability of extracting bridges over water in different directions within the high-resolution optical remote-sensing image, considering both qualitative and quantitative aspects. Therefore, this approach may be useful in updating geographical databases of bridges and facilitating the assessment of bridge damage caused by natural disasters.

Modified Shortwave Infrared Perpendicular Water Stress Index: A Farmland Water Stress Monitoring Method

AbstractCrop water stress monitoring by remote sensing has been the focus of numerous studies. In this paper, specifically red (630–690 nm) and shortwave infrared (SWIR; 1550–1750 nm) wavelength bands are identified to monitor farmland water stress, and a method [modified shortwave infrared perpendicular water stress index (MSPSI)] is developed that is based on the spectral space constructed by SWIR − Red (Rd) and SWIR + Red (Rs). The MSPSI stayed at mostly the same water stress level for full vegetation coverage cases with high vegetation water content and saturated bare soil as well as full vegetation coverage with extremely low vegetation water and dry bare soil in the Rs–Rd spectral feature space. This approach makes the water stress conditions between different covers comparable and the MSPSI applicable to farmland water stress monitoring in different vegetation covers throughout the growing season. To validate the proposed index, the MSPSI calculated from Thematic Mapper images and Moderate Resoluti...

The variation analysis of land surface albedo in Beijing in recent ten years

The surface land albedo is an important parameter of the energy balance. It is very significant for the urban micro-climate and environment to research the variation and analysis of land surface albedo. In this paper, the variation of land surface albedo in Beijing in recent ten years, the correlation of the albedo and underlying surface type, the correlation of the albedo and LST and NDVI were studied based on ETM+ data in 2010 and 1999. The conclusions of the paper are as followed: (1) The average albedo of second, third, fourth and fifth ring in Beijing were gradually increased. The albedo of Beijing area in 2010 reduced 0.0075 compared with 1999; the albedo of main city area within fifth ring road reduced 0.0108; the albedo of the area between third ring road and fourth ring was the biggest drop range area, and it reduced 0.0135; the albedo of the area without fifth ring was the smallest range area, it reduced 0.0048. (2) The average albedo of land cover types in order from high to low: new construction areas, farmland, bare land, woodland, villages, construction zone, paddy fields, water. The change of land surface type led to the albedo difference in Beijing between 2010 and 1999.

Remote sensing information of mineralizing alteration extraction methods

Remote sensing technology is considered a fast and effective method to prospect ore. Now, this method is used in Gejiu tin deposit of YunNan in order to extract more accurate mineralization abnormal information. In this study, first through the band math method and principal component analysis method, the mineralization alternation can be extracted in ETM data. Then using ASTER data the limonitization, the chloritization and the dolomitization are extracted by the spectral angle method. At last, the trace elements of the vegetation are statistically analyzed and the vegetation mineralization alteration information is extracted by two different methods in ASTER data. The result shows that the alternation information distributions are consistent in the east-south study area and match with the field exploration. Consequently the extracted results are effective.

Study on quantitative retrieval of soil nutrients

Soil spectral reflectance is affected by soil physicochemical characteristics and the physical basis of the soil remote sensing. Generally, the impact factors of the soil spectral features include water content, organic matter content, iron oxides content, physical composition and the parent material. In this study, a portable ASD FieldSpec Pro FR was used to collect the spectra of soil samples. The sensitive bands were selected by analyzing the relationship between nutrients and soil spectral features. Then the inversion models of soil nitrogen and organic were established by linear regression separately. The result showed that the content of soil nitrogen and soil organic can be well retrieved from remote sensing.

A component-based system for agricultural drought monitoring by remote sensing

In recent decades, various kinds of remote sensing-based drought indexes have been proposed and widely used in the field of drought monitoring. However, the drought-related software and platform development lag behind the theoretical research. The current drought monitoring systems focus mainly on information management and publishing, and cannot implement professional drought monitoring or parameter inversion modelling, especially the models based on multi-dimensional feature space. In view of the above problems, this paper aims at fixing this gap with a component-based system named RSDMS to facilitate the application of drought monitoring by remote sensing. The system is designed and developed based on Component Object Model (COM) to ensure the flexibility and extendibility of modules. RSDMS realizes general image-related functions such as data management, image display, spatial reference management, image processing and analysis, and further provides drought monitoring and evaluation functions based on internal and external models. Finally, China’s Ningxia region is selected as the study area to validate the performance of RSDMS. The experimental results show that RSDMS provide an efficient and scalable support to agricultural drought monitoring.

Integrating remote sensing and Super-Low Frequency electromagnetic technology in exploration of buried faults

The buried faults are widespread in the coal-bed, which result in great difficulties in the construction work. In this paper, an integrated method is used in coal-bed in order to detect and analyze the characteristics of buried faults. Firstly, the lineaments are interpreted by visual interpretation from the ETM+ image, and several lineaments enriched areas are picked up. Secondly Super-Low Frequency (SLF) electromagnetic detection is conducted in these areas. Finally, combined with the geology information, lineament distribution and the SLF data, the characteristics of the buried faults are delineated. The results show that the near EW trending normal faults exist widely in the study area by this method, and the depth of the buried faults are presumed in 450-600 m that are coherent with the available drilling data.

Feasibility study of building seismic damage assessment using oblique photogrammetric technology

In this paper, the feasibility of building seismic damage assessment using oblique images is discussed. Firstly, some geometric features of buildings are selected and analyzed according to the universal geometric characteristics of most buildings. Secondly, the parameters of each geometric features are calculated by the method of photogrammetry. Finally, the results of parameters calculation are analyzed and discussed. The results show that more information of building can be obtained from oblique airborne images than from vertical images. Furthermore, these information can reflect the conditions of buildings correctly and effectively in three dimensional (3D) space. The conclusion is drawn that it is feasible and potential to conduct building seismic damage assessment based on oblique airborne images.

The quantitative prediction of Coalbed Methane gas content based on super-low frequency electromagnetic technology

Abundant field experiments have showed that the super low frequency (SLF) electromagnetic detector is sensitive to Coalbed Methane(CBM). The signal curves collected by the SLF electromagnetic detector show high amplitude anomalies in the CBM enrichment areas. Based on this finding, we choose the Qinshui basin as study area, and take advantage of the field SLF electromagnetic data to make quantitative prediction of CBM gas content.The results show that the average error between the estimated value and the measured value is 7.56%.