Polarimetric decomposition of fully polarimetric SAR data has been extensively used in land use classification, target detection and identification, and land surface parameter retrieval. At present, two main categories of polarimetric decomposition approaches can be identified, i.e., model-based decomposition and eigenvalue-based decomposition. By combining the advantages of the above two decomposition methods, the hybrid Freeman/Eigenvalue method can deal with the negative power problems, and the decomposed components can be interpreted in terms of known scattering mechanisms. In order to extend the applicability of the hybrid Freeman/Eigenvalue to different types of land cover, the authors propose a novel adaptive polarimetric decomposition method in this paper by coupling the hybrid Freeman/Eigenvalue decomposition and an adaptive volume scattering model proposed by Neumann et al. The performance and advantages of the proposed method were demonstrated and evaluated with AirSAR L-band data over Black Forest in Germany. Comparative studies were also carried out with previous Yamaguchi three-component decomposition and adaptive nonnegative eigenvalue decomposition (ANNED). The results show that the proposed method can effectively avoid negative power problems and is applicable to different types of land cover. Moreover, different types of land cover can be well discriminated by the proposed technique.
The problem whether the threshold value is reasonable is very important to the binary or multi mask image formed under the condition of multi-interference information, and it is really the key to delete the interference information and extract the useful information. In this paper, the author discussed the problem as to whether the method is reasonable or not in judging the threshold value under the condition of forming binary mask image with single interference factor based on different thresholds and deleting interference information based on multi-value masking image with reasonable threshold, with the purpose of extracting the alteration information. The results show that, if the same non- interfering regions can be extracted based on the binary or multi mask image with multi-interference information, the threshold value is reasonable in forming binary mask image with single interference factor, the multi-interference information will underlap each other, the interference information or the false information can be deleted and the true alteration information can be extracted based on the true multi mask image.
With Radarsat-2 as an example, a method of building height extraction from multi-polarization SAR imagery was proposed based on backscattering model. First, the connected component of double- scattering of the buildings in the image was analyzed and its contribution to radar cross section was got simultaneously, which was a case study in urban areas of Beijing. Second, different polarization-scattering vectors were calculated based on parallelepiped- assumption, which was supported by quantifying buildings’ correlation length and the angle between radar’s azimuth and buildings’ main direction. Finally, optimal polarized combination was utilized, which was extracted by using backscattering model from the solution of geometrical optics-physical optics(Go-Po)first-order approximation and comparing the results from different regionally training areas at the same time. The experimental results show that optimal polarized combination produces much less errors than single-polarization imagery in extracting the height of entire experimental area, with 81.43% of buildings having errors less than 5 meters, root mean square error being 4.45, and correlation coefficient with ASTER GDEM being 0.909 5, which proves that the result in height extraction is reliable.
Vegetation is an important kind of objects in remote sensing image segmentation, and vegetation fine-grained segmentation generally has three targets, i.e., arbor, shrub, grass and moss according to the scale. In view of the problem that single level multi-classification method can't make full use of the different scales of the texture of vegetation target so as to achieve more accurate multi-classification, the authors proposed a hierarchical multi-scale remote sensing image vegetation segmentation method based on spectral histogram. First, the vegetation areas in remote sensing images were extracted with the normalized difference vegetation index(NDVI), and then the multiple binary classification algorithm was implemented in the region to achieve multi-classification operation. At each classification level, the advantage of the prior knowledge and texture scale was taken to select texture filtering parameters, the spectrum histogram of each sub-block image was extracted from the filtering result to express texture features so as to achieve the segmentation of a level. The experimental results show that the proposed method uses the prior knowledge and texture scale of vegetation target at all levels, so that the texture filter is made to enhance treatment more targeted, the spectrum histogram feature has much more degree of differentiation, and the accuracy of the vegetation fine-grained segmentation has been improved significantly.
In this paper, the model VUX-1 laser was used as an example to calculate the influence of multitimearound(MTA) on the height of the aircraft. Then according to the requirements of the point cloud density, scanning frequency, scanning speed and other indicators, and in accordance with the principle of air aerial photogrammetry and LiDAR data acquisition specification, the difference between traditional photogrammetry and airborne LiDAR was distinguished, and a cue from traditional photogrammetry was used for reference. The changes of laser range under different conditions, such as the different types of targets in the test area,the different types of targets and the variation of the most remote ranging capability, were determined. By taking into account the above problems,a route for the airborne LiDAR system was designed. At last, the across track point spacing and the along track point spacing were calculated respectively for analyzing the reasons and determining the feasibility of the route design scheme.
High-precision DEM data constitute the basis of watershed hydrology analysis. SRTM 1 Arc-Second Global elevation data, released by US Geological Survey, offer worldwide coverage data at a resolution of 1″ (30 m). In order to evaluate and analyze the potential watershed hydrologic applications of SRTM, the authors used Tanghe watershed in Hebi as the experimental area and airborne LiDAR DEM data as a reference to assess vertical accuracy of SRTM (1″) data and the impact of slope, aspect, land cover on errors of SRTM (1″). Hydrologic indexes based on the terrain, such as Topographic Wetness Index (TWI), Length Slope Factor (LSF) and Stream Power Index (SPI),were computed for analysis. Finally the basin’s characteristic parameters, such as catchment basin area, longest path length, shape factor, curvature coefficient, were extracted from the two DEM data and the results were compared. Studies show that SRTM (1″) DEM data have high precision, the RMSE of the original data is 5.98 m, and the RMSE of the data with the elimination of the plane displacement is reduced to 4.32 m. Hydrological analysis shows that SRTM DEM and LiDAR DEM produce some different results: the average of TWI of SRTM is slightly higher, the average of SLF and SPI is lower and the dispersion degree is smaller. This is associated with the terrain distortion of SRTM DEM in micro-topography and high slope area. The basin parameters extracted from both of the DEM data have smaller differences, which shows that SRTM DEM (1″) has wide application prospects in hydrologic analysis.
The technology of hyperspectral remote sensing has the special advantages in regional alteration information extraction. Hyperspectral mineral mapping has important reference value for hydrothermal uranium exploration. In this paper, the data processing flow of CASI/SASI airborne hyperspectral remote sensing data was established and mixture tuned matched filtering was applied to realize minerals mapping in the Baiyanghe uranium and beryllium ore district, Xinjiang. The results of mineral mapping were evaluated by the field verification and the results show that the accuracy of three kinds of sericite’s mapping is higher than 85% and the accuracy of other minerals’ mapping is larger than 90%. The overlay analysis of uranium ore spots and the results of mineral mapping show that there is a significantly correlation of the characterization of spatial distribution between uranium ore spots and the alteration of hematite and Al-rich sericite. The alterations of hematite and Al-rich sericite are near the contact zone between Yangzhuang rock body and peripheral volcanic rocks and exhibit distinct characteristics of zoning. Furthermore, there may be some differences in the temperature of hydrothermal activity between the north and the south of the deposit according to the spatial distribution characteristics of three kinds of sericite, which indicates the existence of multiple hydrothermal activities in the region. The results obtained by the authors can provide references for prospecting prediction of the periphery of the ore district and regional geological genesis research.
Winter wheat is one of the main food crops in northwest Shandong Province, a main grain production base in China, and therefore the application of remote sensing technique to monitoring the spatio-temporal pattern change of the winter wheat area has the important practical significance. In this study, the appropriate time window was selected according to calendar of main crops in northwest Shandong Province, and then the NDVIs of Landsat TM/ETM+/OLI images were calculated. After that, the threshold value range of NDVI was set to extract winter wheat in 2000 and 2014. Finally, 1404 sampling points were chosen through field survey and Google Earth to calculate the accuracy. The results show that winter wheat is spatially widely distributed in northwest Shandong Province, whereas things in Dezhou Municipal District, Xiajin County, Lijin County, Zhanhua County, Wudi County and Liaocheng Municipal District are just the opposite. The winter wheat area in 2000 in northwest Shandong Province was 1.71×106 hm2 and was 1.49 ×106 hm2 in 2014, with the decreasing range being 2.18×105 hm2 and the rate of change being -12.73%. The accuracy of extraction in 2014 was 96.8%.
In order to study the spatial distribution characteristics of monthly mean NDVI during the past ten years in China, the authors used MODIS MOD/MYD13C2 vegetation spectrum to synthesize monthly NDVI and, combined with China’s terrain data, discussed the changing regularity of NDVI with respect to aspect and elevation.The results show that the area ratio of low NDVI value segment [-0.25,0.15)is high in winter and low in summer, suggesting the characteristics of bare soil, deserted land and water.The median segment[0.15, 0.55] shows the "bimodal double-dip" character, and the area ratio is higher in spring and autumn than in winter and summer, implying features of vegetated mixture land cover.The area ratio of high value segment [0.55, 0.95] is high in summer and low in winter, indicating variation of vegetation cover with seasonal change.NDVI change with aspect shows the "bimodal double-dip" distribution, the NDVI values in southeast and northwest aspects are larger than those in southwest and northeast aspects.With increasing elevation , three NDVI decreasing zones are 250~1 250 m, 2 500~3 000m and 3 750~6 000 m, and two NDVI increasing zones are 1 250~2 500 m and 3 000~3 750 m, respectively.The horizontal and vertical distribution differentiations of NDVI are remarkable, which is attributed to the impact of climate and geographical terrain elements in China.Those regularities may be helpful to the research on land surface process.
The initiative finding of coal fire and timely governing of coal fire so as to quickly and accurately extract temperature anomaly information are of great importance. In this study, with the coal fire area of Daquanhu in the suburbs of Urumqi of Xinjiang as the study area and ETM+ remote sensing data as the base, the authors used generalized single-channel method to retrieve land surface temperature of coalfield fire area, and then used manual threshold method and density slicing method to extract background area and temperature anomaly. Finally, temperature anomaly area image was superimposed upon the magnetic prospecting resultant map to perform analysis. The results show that the retrieved RMSE of Generalized Single-Channel Method is 0.68℃, the overlap rate between temperature anomaly area and definitized fire area range is 82.71%, and the accuracy rate of temperature anomaly area retrieval is 80.17%. This method can preliminarily delineate the coal fire range and also provides a reference for precisely measuring the coal fire range.
Revealing the spatial characteristics of land surface temperature (LST) and its influencing factors is of great significance for environmental changes research. Many studies have examined the relationship between the single factor and LST, but the understanding of the influence of many factors on LST under the background of sunny slope and at the back of the light remains elusive. In this study, the authors divided the area into sunny slope and the back of the light, and retrieved LST based on atmospheric correction method, together with land use changes determined by using remote sensing data. The authors constructed the regression equation between the LST and many factors, such as normalized moisture index (NDMI), normalized difference vegetation index (NDVI), slope, aspect and DEM, for evaluating the influence on LST under the background of sunny slope and at the back of the light. The results show that LST in sunny slope was higher than that at the back of the light within the same elevation and land use, LST decreases with increasing altitude, and the LST in different land uses are not the same. The influencing factors of LST in sunny slope and at the back of the light were NDMI and DEM, the influence degree on NDMI under sunny condition is larger than that at the back of the light. The rest of the impact factors are low, the influence degrees under the sunny condition on NDVI and the slope at the back of the light were the largest. Therefore, the sunny slope and at the back of the light resulted in spatial pattern change of LST in western Sichuan plateau, and the influence degree of its impact factors has obvious primary and secondary order difference.