Qijiang Zhu

A conception of digital agriculture

On the analysis of characteristics of current agriculture, we put forward the conception of digital agriculture, and construct its framework. Relationships between precision agriculture, digital Earth, information agriculture, virtual agriculture and digital agriculture are analyzed. The necessities to put forward the concept of digital agriculture, the feasibility to realize digital agriculture and the measures should be taken are also discussed in our paper.

The study on the method of monitoring and analyzing mineral environment with remote sensing images

The mineral environment of the DeXing Copper, in JiangXi Province in China, is monitored and analyzed by making use of the field spectral data and remote sensing images, TM data as well as ETM data, in different mineral developmental period. The location of the mine tailings is identified and its change in area and volume versus the time is calculated as well. A method to use DEM (Digital Elevation Model) for analyzing the change of the volume for the pollution source and its impact to the local environment is proposed in this paper. It provides the quantitative description for the mineral environmental pollution. This method can be used to monitor the open mineral environment, which has the same environmental problem like DeXing Copper Mine. Its beneficial for the local government to supervise the mineral environmental changes and be aware of the pollution status dynamically and lively.

Interception of PAR and relationship between FPAR and LAI in summer maize canopy

According to our observation under clear and cloudy days during growing season, we analyzed the diurnal changes of the incident PAR, the reflected PAR of canopy and soil, the transmitted PAR, the reflectance of soil, and the absorbed photosynthetically active radiation (APAR). FPAR at an interval of five minutes and the average value of a day are also calculated according to each PAR component in canopy. Then the relationship between daily variation of FPAR and crop growth periods as well as the variation of LAI was also investigated and a linear relationship between FPAR and LAI was presented.

Using images combined with DEM in classifying forest vegetations

More and more different resolution images are used in the process of forests vegetations classifying and recognizing. Most classifying methods, including supervising and non-supervising methods, are based on spectral information and work well in forest vegetations recognizing. But some forest vegetations such as conifer, broadleaf and mixed forest are not distinguished clearly by using these methods just because these vegetations have similar spectral characteristic. In this paper, TM image of Changbai Mountains was obtained and spectral information of the image is analyzed. At the same time, the vegetation types covering the Changbai Mountains are acquired by investigating the region in person. On the other hand, DEM (digital elevation model) is employed as an important criterion in classifying forest vegetations basing on spectral character in this article. The classified results are better than those calculated by original classifying methods. At last, the results are verified by data surveyed on the spot. The results illustrate that DEM is an important factor in classifying forest vegetations distributed by the elevation. Spectrum combined with elevation information is very useful for object recognizing and classifying. Images and DEM have widely practical application and should be used in more research fields.

Quantitative remote sensing research on the vegetation 3-D visual simulation based on object oriented technique

In the field of remote sensing, it is important to understand interaction between light and vegetation. The interrelation of them has been addressed in many works, and many different radiant models of vegetation have been proposed, such as: geometrical optical models, turbid medium models, hybrid models and computer simulation models. With developing of quantitative remote sensing research, computer simulation models, for example, Monte Carlo simulation model and Radiosity show their importance in analyzing the experimental data. In order to continue calculating the reflectivity from the vegetation by using a computer simulation model, it is essential to build the 3D structure of the vegetation. Therefore, many 3D structure data and optical parameters about the real winter wheat were measured firstly, i.e. height of stem, positions and sizes of the leaves, distributions on the field of wheat. Because these data are numerous and discrete, it is very difficult to simulate the virtual scene with them directly. To cope with it, we arranged all data and parameters in several layers based on the object oriented technique. Moreover, in order to simplify and deduce the structural variables that will be applied to build the 3D visual winter wheat model, we analyzed experimental data statistically in the process of realistic structural model. Several geometric and logical relations about structural variables were developed subsequently, and some variables varying with season were summarized to get the simple regulation with the purpose of simulating growing process of the winter wheat. The extended Lindenmayer system (L-system) method is then used to simulate the virtual scene of winter wheat by giving a few structural variables simplified before. Once the simulation is correct, scattering and reflectance from the 3D structural scene can be calculated using the Monte Carlo simulation model or Radiosity and so on. Our results show that (a) our lighting simulation system efficiently provides the required information at the desired level of accuracy, and (b) the plant growth model is extremely well calibrated against real plants. Furthermore, the method and the relations developed in this paper can be used in other subjects, such as computer graphics.

Analysis of the factors influencing surface sensible heat fluxes with large aperture scintillometers

Large aperture scintillometers (LAS), Bowen ratio, eddy covariance measurements, soil moisture in various depths with measuring masses and routine weather observation such as visibility, cloud, wind speed and weather phenomenon with manual work were employed to study sensible heat flux over homogeneous bare soil surface from March 20th to April 20th, 2002, at XiaoTangshan area, Beijing. The diurnal variation of sensible heat flux from LAS is analyzed in this paper, and the relation between sensible heat flux and weather conditions is discussed. Moreover, the correlation coefficient between LAS based surface sensible heat fluxes and the influencing factors such as soil surface temperature and wind speed were analyzed. The analysis will help us to improve the accurate of LAS measurements. Further, the comparisons of the scintillometer flux measurements with the measurements of Bowen ratio and eddy correlation methods were done in order to make more research on scaling-up of surface sensible heat flux from point to area

The BRDF model and analysis of hotspot effect of row crops

According to the Li-Strahler model, a BRDF model of row structure with gap, in which three components and six paths are taken into account, is established through analysis of the process of radiation transfer. The model is verified by the data obtained in the Satellite-Airborne-Ground Synchronous Quantitative Remote Sensing Experiment implemented from March 29 to May 10 in 2001, in Shunyi, Beijing, China. As is shown, the model can demonstrate effectively the reflection of crops with row structure.

The research of soil moisture difference using the delaying effect of the precipitation on the vegetation

A new method to analyze the differences of soil moisture in an area is advanced. Soil moisture is related closely to vegetation growth. An experiment was conducted in the Yellow River Basin in China. The change of vegetation cover is the result of many factors. We postulate that soil moisture in the Yellow River Basin is mainly determined by the precipitation. The delaying effect of the precipitation on the vegetation cover was analyzed in the Yellow River Basin using the cross partial correlation index between precipitation and NDVI. The cross partial correlation index has already excluded the impact of temperature on vegetation cover. Different delaying effects represent different soil moisture. The delaying interval can be adapted to measure soil moisture difference at different levels. On the basis of the above result, the difference of soil moisture in the Yellow River Basin was analyzed, and the difference map of soil moisture in the Yellow River Basin was made.

A correlation comparison for remotely sensed data with different resolutions

More and more high resolution images are used in the process of land use dynamic monitoring and object recognizing. Different resolution images have different capabilities in land recognition and classification. The high resolution images play an important role in this area. This paper uses a model to analyze the spatial correlation among the images of different resolutions. The spatial correlations of different types are calculated and compared within this model. As the analysis illustrates, the spatial correlation decreases with the spatial extension for the city land, whereas it is the reverse case for the plantation under the same condition. Furthermore, the research study on the different resolution images for the same area shows that the images dimensions are varied with the spatial resolution and the spatial correlations are changed with different dimensions. The spatial correlation of large-dimension images is greater than that of small-dimension images. It means the spatial correlation of high resolution images is a little bit higher than that of low resolution images. This study reveals that the spatial correlation can be used in evaluating the information entropy, and is very helpful in object recognizing and classifying.

A study of surface sensible heat fluxes with Large Aperture Scintillometers

Large Aperture Scintillometers (LAS), Bowen ratio and eddy covariance measurements were employed to study sensible heat flux over homogeneous bare soil surface from March 20/sup th/ to April 20/sup th/, 2002, at XiaoTangshan area, Beijing. The diurnal variation of sensible heat flux from LAS is analyzed in this paper, and the relation between sensible heat flux and weather conditions is discussed. Further, test comparisons of the scintillometer flux measurements with the measurements of Bowen ratio and eddy correlation methods show good agreement; The correlation coefficients are over 0.8.