Recently,research on vegetation of land by using“3S”techniques(Remote Sensing, Geographic Information System and Global Position System) have been paid more attention by scientists and researchers in the world. MODIS is one detector board on Terra' s(EOS-AM1), which was lunched on
December 18,1999 by NASA Goddard Space Flight Center of US. This paper studied the Difference among Normalized Difference Vegetation Index(NDVI), Environment Difference Vegetation Index(EVI), Soil Adjusted Difference Vegetation Index(SAVI) and Ratio Vegetation Index(RVI) by using Terra-MODIS data. At the same time, we have studied the temporal and spatial changes on the typical trees in the experiment areas, which will help us get the temporal and spatial change discipline of forest in our country.
Thermal remote sensing imagery has been widely used to reveal urban heat island (UHI) phenomenon since the last two decades. To study the UHI change through change detection technique, it is usually expected to use the thermal data of different years with the same date. However, this is
generally difficult special for the cloudy and rainy areas and the data with different date may have to be used. This will make the comparison of such thermal image data more difficult due to seasonal difference.In order to work out this problem, this paper introduces a method which can reduce the seasonal difference if the images acquired on different date have to be used.The thermal infrared bands of different date were first processed respectively through several image enhancement technologies. This generated 3-dimension-view images and revealed heat characteristics and
spatial distribution features of the UHI. To find out the change of the UHI between different dates, the two thermal images were normalized and scaled to several grades to reduce seasonal difference and then overlaid to produce a difference image by subtracting corresponding pixels. To quantitatively compare UHI, an index, Urban-Heat-Island Ratio Index (URI), was created. It can further reveal the intensity of the UHI within the urban area. The calculation of the index is based on the ratio of UHI area to urban area. The greater the index is, the more intense the UHI is. This makes it possible to quantitatively study the UHI changes within a period of time. The technique has been successfully applied in a case study on
UHI change in Xiamen City of China.
By the field experiment,we achieve the chlorophyll concentration and reflectance of nine groups of rice leaves and investigate the quantitative relationships between them by correlation analysis.The results reveal that they have good relationship in the range of 450～686 nm and 750～770 nm, and the peak of the correlation is at the wavelength of 686nm.Meanwhile, we find strong correlation between the wavelength of the Red edge inflection point and the chlorophyll concentration of the rice leaves(R2=0.88), and then discuss the feasibility of exploring the rice chlorophyll concentration by way of hyperspectral remote sensing.
Various equations about Landsat data and measures of aquatic suspended solids concentration have been mentioned in literature. Most of them are nonlinear and can be transformed to linear polynomials with unknown parameters inXandY. In order to fit these linear polynomials, scientists input
different parameters manually, and get fitting polynomial with maximal correlation coefficient. The method has low efficiency. The article presents a kind of iterative algorithm, which calculates automatically from initial values of unknown parameters and corresponding interval according some rules
until get the fitting polynomial with maximal correlation coefficient. The algorithm has good effect in practice and is all-purpose for other fields.
Scientific and rational analysis of market demand and site selection becomes the important basis of retailer' s investment decision. First, this paper introduces basic course and corresponding analytical method of the retail market area analysis. Second, on the basis of commercial geographical information management system, we structure three commercial application analytical models: analyzing of the index of retail saturation, market area dividing, estimating of the demand of retail stores, having realized the ration and visual analysis of the market area. Finally, we take the hypermarkets in Xuhui District of Shanghai as an example to test the model.
Airphoto is center-projectioned, which has a lot of errors, mainly involving projection distance,tilt and projection difference, compared with orthorectified projection system. These errors result in scale difference in airphoto.The more the errors have, the more different the scales have. These errors greatly hinder the airphotos' application. So how to measure airphoto scale is the key of airphoto application.Normally, the scale of airphoto includes main scale, average scale and point scale. This paper discussed how to measure any point scale in airphoto in detail after calculating main scale and average scale. The results of studying area showed that when the elevation difference is 47.5 m, the scale difference is 5.7%,when the elevation difference goes up to 100 m, the scale difference is up to 12.9%; The main scale is poorest, and the average scale has good accuracy but is only adapted to smooth areas, and point scale can be used to calculate scale of any point in airphoto and also has good accuracy.
SIR-C is the first spaceborne imaging Radar system with multi-wavelength and quad-polarization developed by joint effort of U.S, Italy and Germany. Polarization SAR measures the scattering matrix of each pixel on ground and synthesizes the image at given orientation and ellipticity angle, including linear and elliptical polarization. It has many advantages over single or multi-polarization SAR in detecting objects, identifying targets and extracting texture. Based on SIR-C data of Hetian prefecture in Xinjiang of China, this paper presents the basic principle of polarization synthesis and the processing flow of SIR-C data, analyses the polarization signal of four typical ground objects and makes experiment of extraction of quad polarization SAR data using supervised classification method. The experimental result shows that the polarization signal of ground objects vary greatly with the characteristics of geometry and distribution of the objects, on which quad-polarization SAR data can synthesize certain images to sharpen the contrast of the objects to achieve better classification result and more effectively extract the information. So quad-polarization has wide applications in survey of land cover and inversly extracting parameters of ground objects.
Synthetic Aperture Radar(SAR) images of same scene may have obvious difference in gray-level characteristic because of correlation noise and different imaging conditions. Method based only on edge feature or gray-level information doesn' t adapt to SAR image registration. This paper describes a new feature-based approach using edge information of typical objects combined with local gray-level statistical information to image-to-image registration. First, local area with typical object is selected instead of the whole image registration to reduce computation time. In each area, edge feature of the typical object is extracted and initial feature point set is decided according as shape information of the points on edges.Then, a principle combined with edge shape and gray-level information is used on feature point matching to reduce the effect which the accuracy of edge extraction may add on the accuracy of registration. At last, a root mean square error is computed. Experimental results with pixel level accuracy on Radarsat imagery proves the validity of this approach.
This paper studies Active Coded Radiometric Calibration Technique (ACRCT) of SAR. ACRCT has been widely studied as SAR calibration technique. In some calibration sites, background is complicated, which will affect the radiometric calibration precision. The influence of background clutter
signal to the precision of radiometric calibration is analyzed, and an equation to calculate system transfer function error is proposed. With this equation, some simulation experiments are carried out. The principle and signal processing flowchart of ACRCT are studied in detail. Two clutter models are built and based on them, ACRCT simulation experiments are carried out. Experiment results testify that ACRCT can effectively restrain the influence of background clutter signal and improve the precision of radiometric calibration of SAR, especially enhance flexibility of choosing calibration field.
In the light of the blindness search theory, this paper introduces a new method for half-automatic converting raster data to vector data. This method assumes that raster data is a collection of points and vector data is a collecton of lines. The converting process is mainly the process of connectting points with lines. Firstly, you must point out the start point and its characters, then search the points with the characters around the start point in a predefined distance with help of computer. According to the history searched points,computer will select one point from the searched points, and replace the start point with this point, and repeat searching till there is not point searched or you stop the search process. By linking the searched points,the computer completes a converting. This method does not need to pre-process the raster images, and process the true color image expediently, so it has high efficiency and high speed. The experimental results are very good.
There exist bowtie effects in MODIS L1B data because of the Earth' s curvature and the characteristics of MODIS detector, namely some datum is overlapped at the edge of a scan. Bowtie effects can' t be eliminated after geometry calibration, so eliminating bowtie effects has to be done before geometry calibration. It can be eliminated using ephemeris which is complex and difficult for common user to get ephemeris. We used two simple methods and compared their location accuracy after geometry calibration in this paper.
Digital orthophoto map has many advantages compared to digital line graphic. The digital orthophoto map is broad applied in city planning, land use managing and route planning of railway and highway. This paper mainly introduces how to make the digital orthophoto map with SPOT data using
ERDAS.
It is the GIS developing direction to integrate GIS with Internet. Internet GIS is not only used to publish distributed geographic information on line, but also to provide on line tools for distributed geographic information real-time analysis and processing. Internet GIS should make use of existing multi-
sources and functions for geographic information analysis and processing. In other words, it must solve the problem of interoperability. This paper deeply researched the development and core technology of GML3.0(Geography Markup Language). The major contents included data type, feature, feature collection,types and elements of geometric model,temporal and coverage.Some content models and UML representation of correlative contents were presented. The paper also presented the application instance of data sharing and operatability by using GML3.0 and forecast the future version.
