Precision-farming is an essential part of modern agriculture. Precise management could be achieved by acquiring the field information on crops and their growing environment. Field management such as seeding, fertilizing, irrigating and harvesting could be optimized according to the spatial and temporal difference in crop and soil status. Along with the fast development of remote sensing technology, this technology has become an essential component part of precise farming and has been widely used in providing guidance for irrigation, fertilization, weed control, pest control and harvest. Remote sensing can be used to provide basic information of the field (field infrastructure and plot distribution) for farming management as well as to monitor dynamics of crop growing and such relevant environment factors as soil nutrition, soil moisture, crop nutrition and crop pest status in the field. The advances in applying remote sensing in these fields were reviewed and commented in this paper. Based on a review of the current application of remote sensing in precision farming, this paper describes in brief its research situation and gives a vista of its development. It is pointed out that improving the monitoring method, applying new data, integrating multi-source remote sensing data, integrating remote sensing data with agro and crop models and systemization are the key points in this field. Further researches on this field will promote the application of remote sensing in precision farming.
As SMOS(Soil Moisture and Ocean Salinity)mission has been carried out smoothly, and AMSR-E (Advanced Microwave Scanning Radiometer-Earth Observing System) services have been conducted, people have achieved another great leap forward in monitoring surface soil moisture by satellite-borne microwave radiometer in space technology. Since space resolution is coarse under satellite microwave radiometer, the accuracy of retrieving soil moisture has been conditioned by space heterogeneity and relief effects. Mountainous terrain on a larger scale than wavelength has such significant effects on passive remote sensing as altitude role in microwave transmission path, topographic slope angle and aspect effects on surface emissivity, and multi-reflection between mountains or shadow effect on the change in surface scatter characteristics. A number of studies on relief effects of microwave radiation have been carried out both at home and abroad, and some simple topographic correction methods have been advanced. Based on the physical mechanism of electromagnetic waves and the statistical analysis, the authors first investigated the relief effects on microwave radiation and inversion of soil moisture, then made a review of the newest advance in relief effect researches on passive microwave remote sensing, and finally pointed out problems existent in current studies as well as orientation for further studies.
With the uranium exploration as an example, this paper puts forward a new concept of post-remote sensing application technology based on the thinking of the comprehensive research and deepened application of remote sensing information. This new concept is considered to be an important way to promote the application of remote sensing information from technology to science. On such a basis, the viewpoint of fault-uplift mineralization of sandstone-type uranium is proposed and a model of regional prospecting for uranium in the craton and activated basin of China is established. Under the guidance of the viewpoint and the model and by using the new technique, 3 uranium mineralization belts were found in the Kalpin fault-uplift on the northern margin of Tarim basin, thus achieving good prospecting result.
Based on a comparison of the monitoring results of land use dynamic monitoring in 2008 and in different periods of time in Tianjin, the authors have analyzed the differences between the results of annual monitoring and quarterly monitoring from the angles of time factor and human factor. The approaches to the problems as to how to effectively improve the two kinds of monitoring are discussed. Considering the limitation of the data source and the information extraction methods, this paper focuses on the analysis of the improvement and optimization of the results of quarterly monitoring of land use by using the remote sensing information extraction methods. The indirect and circular methods are used in this paper which can facilitate remote quarterly monitoring in a more efficient and targeted manner.
Algorithms for identifying convexity-concavity of a simple polygon has a very important application in many fields. The authors analyzed the present popular algorithms for identifying convexity-concavity of a simple polygon such as angling method, left-right-point method, vector-area method, vector-product method, raying method, slopping method and extremity-vertices-order method. A detailed derivation of these algorithms has revealed that these algorithms can all use the formula b=p*m as the expression, and are equivalent to each other in nature; nevertheless, the pole-order method still have some problems to be further studied. Based on an analysis of the computation, the authors hold that theoretically the vector-product method, the slopping method and the raying method could be used effectively in programming.
The technique of multi-angle polarization detection is described briefly in this paper. Based on experiments, the authors analyzed in detail polarized characteristics of the oil pollution object. The spatial characteristics of the spectrum of polarized light are discussed from the mechanism of polarization detection, and three universal laws are summarized. In comparison with intensity spectrum, small discrepancy of the object is enhanced, especially in the case of polarized light incidence at a large angle. Multi-angle polarization remote sensing has wide application vista in water environment monitoring and object identification.
The traditional segmentation of typhoon cloud based on mathematical morphology usually uses round or diamond-shaped template to segment satellite images. This conventional approach fails to keep a good typhoon original form information after large or multiple erosion or dilation. In order to solve this problem, the authors studied the theory and method of typhoon segmentation with priori features in this paper. Concretely speaking, the authors first extract the general form of typhoon cloud as a morphological template, and then extract typhoon cloud by morphology methods. With TBB data of FY2C, NO.200809 typhoon obtained at 6:00 p.m on July 28 as an example, the authors made a template according to the shape of the typhoons to erode clouds images, and then made a detailed comparison as well as analysis of different template shapes or sizes of the cloud segmentation results. The results show that the priori features templates segmentation results can not only well retain the characteristics of typhoon cloud but also preserve most information after cloud erosion.
In order to obtain the best dynamic simulation method for the Leaf Area Index (LAI) of the spring wheat in Ningxia irrigation area, the authors, based on the spring wheat LAI data observed over the land from the typical agrometeorological experiment station in Ningxia irrigating area, used the agrometeorological method and the remote sensing inverting method to simulate the dynamic changes of the LAI and then to compare the simulation accuracies of the two kinds of methods. The best simulated model for the spring wheat LAI in the whole growth period was eventually obtained. It is revealed that, when LAI is less than 4.5 and PD is less than 40,the remote sensing inverting method should be adopted for simulation,and when PD is more than 40,the agrometeorological method should be employed,and only by combination of the two methods can the best result be achieved.
The absence of two infrared bands (i.e. 1.55~1.75 μm (TM 5) and 2.08~2.35 μm (TM 7)) in CBERS CCD camera compared with Landsat TM/ETM+ results in a limitation that many algorithms developed for TM/ETM+ images are not applicable for CBERS CCD camera data directly. In this paper, a cross-sensor image learning approach is used to simulate new Landsat-like infrared bands so as to extend spectrum coverage for CBERS CCD camera data. A support vector regression (SVR) technique is used to model nonlinear relationship between a priori knowledge from ETM+ DN values and four CBERS CCD bands, and then new CBERS CCD bands are predicted. Experimental result shows good correlation between simulated band and corresponding ETM+ band.
Based on several altered rocks in the Chambishi copper deposit and the spectral characteristics of the rocks existing in VNIR-SWIR bands of ASTER data,the authors adopted the methods of Relative absorption-Band Depth(RBD)and band ratio to enhance the mineral alteration information in this paper. The band ratio of ASTER 2/ASTER 1 and the RBD of ASTER 3 were used to enhance the chalcopyrite and pyrite information,the RBD of ASTER 8 was used to enhance biotite and calcite information,and the RBD of ASTER 6 was used to enhance the sericite information. To improve the existing method of Crosta principal component analysis,the authors applied the combination of the enhanced band ratio and RBD to Crosta method with the purpose of extracting the alteration information of the copper deposit and neighborhood areas in Chambishi. As proved by known copper deposit locations and geological analysis,the methods mentioned above can effectively extract the alteration information and distinguish the main minerals in the study area. The results are reliable,thus supplying references to the extraction of alteration information.
Based on the CHRIS/PROBA hyperspectral remote sensing data,the authors retrieved the leaf area index (LAI) by A two-layer Canopy Reflectance Model (ACRM). The process consists of three main steps: Firstly,the high-spectral data was preprocessed and statistically analyzed. Secondly,sensitivity of the model to observing directions was analyzed. And finally,the best combinations of bands and parameters for the study area were chosen. The process was used to study the LAI of typical grass plots of Xilin River basin in Inner Mongolia. The results show that the application of CHRIS/PROBA data to the inversion of sparse grassland LAI is practical,and the multi-angle information of CHRIS/PROBA data has the potential advantages in decreasing the extent of LAI underestimation.
This paper discusses the rapid production of orthophoto in the situation of flight pattern of aero geophysical exploration. The Thiessen polygon method is used to build sampling area and automatically generate orthophoto of the measured area, with no need to carry out manual edge processing. Considering the characteristics of inmagnanimous images with large quantities of data, the authors propose a method characterized by demonstration, roam, and zoom of magnanimous image based on pyramid memory scheduling strategy of piecemeal and graduation.
The authors tried to extract alteration anomalies in spectral characteristic space (scatter plot) in view of the limitation of the traditional methods. The scatter plot takes on an anisotropic feature in associated distribution of RS data’s grey scale. The distribution is usually combined by oval clusters. Parameters of oval clusters are acquired sequentially by applying U-Statistic method in the frequency of the scatter plot. Through mapping the points inside the oval into RS image and interpreting visually, the spatial distribution of alteration anomalies is obtained eventually. In this paper, this new method was described with the instance of Bayinshan area in Qinghai province. Other data acquired were also comparatively studied, and it is found that the anomalies of ferruginization and argillation are consistent well with each other. This new method has a better performance than PCA in the study area.
Damage estimation caused by an earthquake is a major task in the post-disaster mitigation process. To enhance the relief and rescue operation in the affected area, it is required to receive rapid and accurate knowledge about the conditions of damaged area. Remote sensing techniques were proved to be useful in the last decades in detecting, identifying and monitoring the impact and effect of natural disasters. Recently emerging LiDAR data provide the height of the ground objects, which can be used to extract the collapsed building in a complex urban environment. Using the aerophotographs and the normalized digital surface model (nDSM) extracted from LiDAR data, the authors developed a method based on OBIA and SVM for extracting the earthquake-caused collapsed building. The test study in Port-au-Prince, Haiti’s capital, after January 12,2010 earthquake shows that the method can extract collapsed buildings with high accuracy of 86.1%.
To tackle the limitation of conventional pixel-based classification methods, this paper proposes a new approach composed of three steps, namely kernel principal component analysis (KPCA) based feature extraction, support vector machine (SVM) classification and majority filtering post-classification. An experiment with an IKONOS image covering a study area in Tibet indicates the effectiveness of this approach. The resultant image from this automatic method shows a pattern very similar to the pattern of the reference map interpreted manually.
Based on the measurement of the ground spectral reflectance of basal land covers and the accurate atmospheric correction for Landsat TM data,the authors improved the linear spectral mixture model (LSU)and developed a vegetation coverage retrieval model suitable for southern China. The effects of the atmospheric environment and the imaging time of remote sensing data were both reduced,contributing to the multi-temporal comparison,by the utilization of the ground spectral reflectance from field survey. The soil moisture factor was considered to eliminate its remarkable spatial differentiation error in southern China. The vegetation coverage retrieval model was proved to be efficient with high precision over the in situ field verification and was applied to extract the vegetation coverage information in Guangzhou from 1998 to 2009. It is inferred that the urbanization, the large-scale architectural engineering and the reclamation activities constitute the main factors responsible for the formation of the spatio-temporal vegetation change in this area.
Using TM data acquired in 1986 and 2006 and supported by the technology of geographic information system(GIS)and the principle of landscape ecology,the authors selected some indexes of landscape heterogeneity. Taking the Pingguo County of Guangxi,a typical area in the Youjiang valley area,as the study area,this paper analyzed the landscape pattern and its dynamic change characteristics of the study area in the past 20 years. The results show that the general trend of the land-use change from 1986 to 2006 in the study area was the increase of forest,unused land and residents,and the decrease of grassland,farmland and water area. All kinds of landscape indexes of land-use change indicate the space-time response obviously,and the diversity of landscape becomes more evident. On the other hand,the dominance and fragmentation of landscape and fractal dimension become smaller,which suggests that the whole landscape of the study area is developing in the ideal direction.
According to the Characteristics of the ASTER data,the authors calculated the atmospheric transmittance using the MODIS data from the same satellite,and then obtained the surface emissivity by means of the classification result on visible and near-infrared bands as well as the spectral library supplied by JPL (Jet Propulsion Lab). After that,the Land Surface Temperature (LST)was estimated by the split window algorithm. On this basis of LST retrieved from ASTER data,the authors analyzed quantitatively the urban thermal environment in Cangzhou area using the LST,the classification results and the Normalized Difference Vegetation Index(NDVI). These results can provide a certain scientific basis for the further exploration of the developmental rule of the urban heat island,the simulation regulation and the control and optimizing configuration of the urban thermal environment.
The lighted area, night light intensity, compounded night light index (CNLI) and total night light index (TNLI) of 16 cities in the Yangtze Delta were derived from the DMSP/OLS night light data in 2008, and their correlations with urbanization statistics were calculated respectively. Of these factors, the night light intensity proved to be an effective indicator for assessing the urbanization level. Construction land information of urban agglomerations in 1998, 2003 and 2008 was also extracted from DMSP/OLS night light data after the determination of the threshold value. Then the pattern and process of urbanization in the Yangtze Delta were analyzed and the expansion process of buildup area was categorized into several types. During the study period, urban agglomerations in the Yangtze Delta had three typical spatial expansion modes, of which the polygon mode could be observed in all the cities, the linear mode exists along main highways and railways, and the point mode occurs mainly around the less important cities. In spite of the imbalance of urbanization level within the study area, the regional differentiation was lessened gradually. According to the variation of the threshold value from 1998 to 2008, 11 cities, namely Zhenjiang, Changzhou, Yangzhou, Wuxi, Suzhou, Nantong, Huzhou, Jiaxing, Shaoxing, Zhoushan and Taizhou, belonged to the filling-in dominant type, Nanjing, Hangzhou and Shanghai belonged to the first-extension-then-filling-in dominant type, and Taizhou and Ningbo belonged to the first-filling-in-then-extension dominant type.
In order to extract surface collapse’s boundary and calculate its area precisely,this paper summed up the identification keys to hazards and introduced a method for extracting the boundary of surface collapse. In this method,high resolution remote sensing image is used as the data source. Based on image fusion,the authors applied the Robert and Directional operators to the fused image respectively. Next,the first band in the original and two enhanced images were used to form false color image(Original,Robert and Direction enhanced image,ORD). Finally,the surface collapse area was calculated using ArcGIS software. The results show that the method can highlight the boundary of the surface collapse and reduce the error of the area calculation effectively.
By adopting the energy equilibrium theory,MODIS image data were applied to the inversion of the surface Evapotranspiration (ET) in Shiyang River basin,and the average daily ET in Shiyang River basin in January,April,July and October was estimated respectively. It is shown that ET in January is 0.15~7.21 mm; ET in April is 0.89~7.86 mm; ET in July is 0.12~9.08 mm and ET in October is 0.54~8.33 mm, mainly distributed in the Dajing Rriver,Gulang River,Huangyang River,Zamu River,Jinta River,Xiying River,Dongda River,Xida River and the water around Qilian Mountain area. The method of fractal image section line was used to describe the local and micro-structure characteristics of the remote sensing ET in the study area,thus the differences and trends of ET spatial distribution were understood(in January and July,the profile line of fractal number is larger,the profile curve undulates up and down,the ET gradient is bigger and distributed unevenly; in April and October,the profile line fractal number is less than that of January and July,the profile curve is quite gentle,and the ET level is smaller and distributed uniformly). The actual ET was calculated by using the FAO Penman-Monteith equation,and the indirect precision evaluation was made for the remote sensing ET. The results show that the estimated ET results are reasonable and have high precision.
Based on multi-source remote sensing data, rainfall data, DEM and soil property data obtained in northern Hebei, the authors used Universal Soil Loss Equation (USLE) to make a quantitative analysis of soil conservation capacities with the support of GIS technique. Then the soil conservation capacities were converted into capital stocks by making reference to the Specifications for Assessment of Forest Ecosystem Services in China, which was stipulated on May 1, 2008. Two kinds of ecosystem service values were considered, i.e., the value of preserved nutrient and the value of fixed soil. The results reveal that the total soil conservation capacity of northern Hebei was 7.55×108 t in 2008, and the corresponding value of this ecosystem service was 1.08×1012 Yuan. The soil conservation capacities and soil conservation values of woodland, scrubland and grassland are the largest three among the seven kinds of ecosystem values, so these three ecosystems play key roles in conserving soil in northern Hebei.The spatial distribution characteristics of soil conservation values of northern Hebei show that the average value of central mountain areas is higher than the average value of western plateau and eastern plain, because dense vegetation prevents soil from erosion in mountain areas and soil erosion intensity is slight due to flat terrain in the western and eastern parts. For solving the problem of soil erosion in northern Hebei, natural vegetation should be protected, especially in central mountain areas.
In the farming-pastoral area, the land types are complex and the mixed pixel phenomenon is serious, so the automatic extraction of wetland information is difficult. In view of the characteristics and difficulties of wetland remote sensing information extraction in these regions, the authors selected the TM remote sensing data covering Dacangxiang area in Duolun County to study a new method of wetland automatic extraction. Firstly, the NDVI threshold method was used to extract water body and then water types were extracted using water body shape features such as area (s), perimeter (p) and shape index (k). Afterwards, the linear spectral mixture model (LSMM)was chosen to extract wetland information after water removal. Finally, the meadow component which was decomposed by LSMM was amended by SPOT-5 satellite image to further extract high coverage, medium coverage and low coverage meadow. The results show that the overall accuracy of the wetland information extraction is 85.3%, and the Kappa coefficient is 0.79. Compared with the results of the traditional maximum likelihood method, the overall accuracy is improved by 19.9% and the Kappa coefficient is improved by 0.22. This method can provide a reference of remote sensing information extraction of wetland for other regions with mixed spectral characteristics.
Based on the QuickBird panchromatic image of the loess plateau,the authors designed four geometric rectification modes including polynomial transformation and ortho-rectification by making reference of points measured by GPS in the field and reference of rectified 1∶10 000 topographic maps. The experiment results show that 1 with the even distribution of different numbers of GCPs,the range of residual error of GCPs is much wider than that of the RMS of rectified image in each rectification mode; 2 among the four rectification modes,the GPS point-ortho-rectification mode has the highest accuracy,followed in succession by 1∶10 000 topographic map-ortho-rectification mode, GPS point-polynomial transformation mode and 1∶10 000 topographic map-polynomial transformation mode. The highest accuracy for each mode is 2.33 m, 4.30 m, 6.91 m and 7.42 m respectively; 3 the GCP number is positively correlated with the accuracy of rectified images except for the GPS points- ortho-rectification mode.
With the geo-statistical theoretical model and GIS technology, three periods of landscape data from 1987 to 2007 in Yancheng coastal area were assessed for ecological risk and analyzed for spatial variability. Some conclusions have been reached: 1 With the growing intensity of human activities in coastal wetlands, the size of natural wetlands gradually decreased, and the disturbance gradually increased in coastal area. 2 The ecological environment of this area was subjected to increased interference of human activity and landscape fragmentation from 1987. The change of landscape structure led to significant differences in risk indexes of landscape ecology in time and space. The landscape ecological risk of Yancheng coastal area tended to expand. 3 The degree of spatial variability increased in these 20 years. In 1997, spatial heterogeneity of random party was the largest, and the space-related degree was the largest in landscape ecological risk. 4 From 1987 to 2007, the scale and direction of spatial heterogeneity (autocorrelation) of landscape ecological risk in Yancheng coastal area also changed significantly. 5 In each period, the variation in EW direction was larger than that in NS direction. In EW direction, the intensity of landscape ecological risk changed from low to high and then to low again.
In order to evaluate the performance of monitoring land cover change in mining areas by BJ-1 small satellite remote sensing data, the authors made an experimental and comparative study of several change detection methods, with the east coal mining district of Xuzhou City in Jiangsu Province as the study area. Direct change detection methods based on image information operation and image information transformation as well as the post-classification comparison method were adopted in the experiment. The results show that the change vector analysis can attain the highest accuracy, followed by the method of image ratio method, image differencing and multi-band principal component analysis. Through the change detection process, several areas with great land cover change were detected, such as Qingshanquan, Hanqiao and Dongzhuang mining areas in northern east mining district and Dahuangshan mining area in southern east mining district.
The water-leaving reflectance spectra of seawater were obtained through data collected at the Pearl River Estuary in May, 2009. Their negative natural logarithmic values were also acquired by calculation. The correlation coefficients between secchi depths and water-leaving reflectance spectra of seawater and their negative natural logarithmic values were calculated. The correlation coefficients between secchi depths and negative natural logarithm values of water-leaving reflectance spectra of seawater are about 11% higher than the correlation coefficients between secchi depths and water-leaving reflectance spectra of seawater. According to the analytical result, the water-leaving reflectance spectra of seawater and their negative natural logarithm values whose correlation coefficients are maximum and whose locations are Hyperion satellite center wavelength were selected to formulate linear, polynomial, power and exponential regression equations which were used to fit seawater clarity. It is found that the power regression equation fitted by the negative natural logarithm values of water-leaving reflectance spectra of seawater at 559 nm can receive better results. The fitting degree R2 is 0.922 2 and the average relative error is 18% for the tested samples. The result obtained by the authors can provide support for retrieval of seawater clarity in South China Sea shore by satellite remote sensing.
The multisource geographical data may correspond to the diversity of storage formats and, as a result, the storage formats fail to carry out relevant interoperation and spatial analysis, which hinders the information sharing. The authors have hence developed a model for transformation from the Excel data file to Shapefile vector files by virtue of a secondary development based on the ArcGIS Engine modules, which include file access, defining the spatial reference, transformation of spatial and attribute information. As a more visualized expression, this data management method has preliminarily filled the gap between various geographical data and provided the sharing or operating. At the same time, the exploitation right file transformation from Access to Excel and then to Shapefile formats has realized, which is also a transformed expression with the nature of non-destruction, dimensional reduction and visuality in comparison with that of the original files. The essence of this method lies in resolving the information as the record format into the spatial and attribute format. The former format means the superposition of exploitation layer and corresponding remote sensing image, and seamless connection exists between the latter (like mineral species, mining pattern etc.) and the former. On such a basis, the exploitation information of the present situation can be obtained, and the remote sensing monitoring of mineral resources can be carried out.
