Search

Quantitatively evaluating the functions of CO2 fixation and O2 production is important in the study of ecological systems.This article attempts to measure and evaluate the rate of carbon fixation and oxygen release in terrestrial ecological systems using remote sensing,to provide baseline data for the regional environment.Changing land use and land cover types influence vegetation composition and health,so understanding the effects of these changes on carbon fixation and oxygen production provides an important tool for monitoring ecosystem responses to environmental change.Solar radiation is the primary source for physical and biological processes in the atmosphere and on the surface of the earth.This is the only energy source used by green plants during photosynthesis.Green plants produce all organic assimilates through photosynthesis.Net plant productivity(NPP) is the total amount of organic matter accumulated by vegetation per unit area and time,and equals the difference between the carbon absorbed by photosynthesis and the carbon released by autotrophic respiration NPP reflects not only the productivity of a plant community in its natural environment,but also its ability to sequester carbon.The balance between carbon fixation and oxygen production plays a key role in global biogeochemical carbon cycles.So,carbon flows through an ecosystem are an important determinant of the ecosystem′s ability to act as a carbon sink.Using remote-sensing images and precipitation,temperature,and total solar radiation data from1998 to 2007,and a light utilization efficiency model,we studied the effects of changes in these parameters and land use and cover types on the ability of plants to fix carbon and produce oxygen in the Guanzhong-Tianshui economic region.The results show: 1) the economic value of carbon fixation is 22.635 billion yuan/a in the Guanzhong-Tianshui economic region.Over the past ten years,the highest value of carbon fixation was in 2005 at 30.173 billion yuan/a;the minimum was 15.906 billion yuan/a in 2002.By taking an average of the two measuring methods the value of oxygen released,the average value is 24.045 billion yuan/a,more than 1.41 billion yuan a-1 higher than the value of carbon fixation.2) From the perspective of land use types in the Guanzhong-Tianshui economic region,forestland grassland cultivated land other types.From 1998 to 2007,the value for farmland converted to forest land or grassland for average carbon fixation and oxygen production has increased by 1614.29 yuan · hm-2 · a-1 and 1,960.67 yuan · hm-2 · a-1,respectively.Forest land and meadow changed to cultivated land has had the average value for carbon fixation and oxygen production reduced to 1,081.37 yuan · hm-2 · a-1 and 1706.60 yuan · hm-2 · a-1,respectively.3) From a spatial distribution perspective,unit area value of carbon fixation and oxygen production in the southern counties is higher than in the northern counties of the Guanzhong-Tianshui economic region with the value gradually declining from the south to north.By examining the values of carbon fixation and oxygen production based on the NDVI data in various climate scenarios,we were able to explore the influences of land use and cover changes on carbon fixation and oxygen production,as well as the effects of climate change.Carbon fixation and oxygen production in northern China′s agriculture and animal husbandry region and the endangered central loess region—which has serious soil erosion and high evaporation rates is—declining in value.Therefore,study of this fragile ecological environment is relevant.

The real-time correction algorithm is proposed,which adjusts the integration time adaptively according to the current scene information in the process of correction.Firstly,the background images are stored at different integration time and the integration time is adjusted by the specific thresholds.Then the corresponding background image is subtracted from the output of IRPPA and the result are taken as the input of neural network.So it can make up the deficiency of neural network,and reduce the non-uniformity caused by the change of integration time.Experiments of real IRFPA videos show that the proposed algorithm insures high quality of image,also has the advantages of integration time adjusting adaptively and real-time correction.

To measure accurately the attitude of a spatial object that was fast-changing in a suspension state,an attitude measurement method was proposed based on three linear CCD cameras for measuring multiple point cooperation targets.By proposed method,the nonlinear systemic errors and more calibration parameters caused by more overconstraints for camera positions were overcome in the traditional linear CCD attitude measurement.Three 1D cameras composed of linear CCDs and cylindrical lenses were used to measure simultaneously the multiple point cooperation targets on the measured object.Aiming at the restriction of measuring principle on the attitude angle,the simulated calculation method was used to calculate the attitude angle range and the BP neural network was taken to calibrate the CCD cameras and give the spatial 3D coordinates of point cooperation targets.Furthermore,an attitude calculation model based on Rodrigues parameters was established to solve the attitude angles of measured objects.Experimental results indicate that the measurement accuracy of spatial point position and the calculating precision of spatial attitude angle in this system are higher than those of traditional methods,which verifies that this attitude measurement method is feasible and available to measure the attitude.

An exterior attitude calculation method by taking Rodrigues parmeter as the attitute representation parameter was presented to overcome the shortcomings of the constraints and complexity of traditional attitude calculation algorithms and to increase the real-time performance for the multi-linear CCD spatial object exterior attitude measurement system.A multi-linear CCD exterior attitude calculation model was deduced based on the high efficiency of the Rodrigues parameter and the relationship of the intersection vector between the line segments composed of point cooperation targets.In order to avoid the singularity in attitude calculation,a switching theory of the Rodrigues parameters is combined in the algorithm and the process of this attitude calculation method was also given.Experimental results indicate that the computational-complexity of the proposed algorithm is reduced by 37.6% as compared with that of the quaternion method on the premise of assuring precision, and it is superior to quaternion method in real-time performance.At the same time,it avoids the singularity problem.