It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively. 相似文献
The high spatial resolution and temporal observation frequency of HJ-1/CCD make it suitable for aerosol monitoring. However, because of the lack of a shortwave infrared band, it is difficult to use HJ-1/CCD imagery to retrieve aerosol optical depth (AOD). We developed a new algorithm for HJ-1/CCD AOD retrieval by introducing MODIS surface reflectance outputs (MOD09) as support. In this algorithm HJ-1/CCD blue band surface reflectance was retrieved through MOD09 blue band surface reflectance by band matching of the two sensors. AOD at 550 nm was then generated through a pre-calculated look-up table for HJ-1/CCD. Eighteen HJ-1/CCD images covering the Jing-Jin-Tang (Beijing-Tianjin-Tangshan) region were used to retrieve AOD using the new algorithm, and the AODs were then validated using AERONET ground measurements in Beijing and Xianghe. The validation shows that compared with AERONET ground measurements, 27/29 AODs have error less than 0.1 in absolute value. 相似文献
Based on analyzing the relationship between the atmospheric downward radiance and surface emis- sivity, this paper proposes a correlation criterion to optimize surface temperature during the process of temperature and emissivity separation from thermal infrared hyperspectral data, and puts forward the correlation-based temperature and emissivity separation algorithm (CBTES). The algorithm uses the correlation between the atmospheric downward radiance and surface emissivity to optimize surface temperature, and obtains surface emissivity with this temperature. The accuracy of CBTES was evalu- ated by the simulated thermal infrared hyperspectral data. The simulated results show that the CBTES can achieve high accuracy of temperature and emissivity inversion. CBTES has been compared with the iterative spectrally smooth temperature/emissivity separation (ISSTES), and the comparison results show that they have relative accuracy. Besides, CBTES is insensitive to the instrumental random noise and the change of atmospheric downward radiance during the measurements. As regards the noniso- thermal pixel, its radiometric temperature changes slowly with the wavenumber when its emissivity is defined as r-emissivity. The CBTES can be used to derive the equivalent temperature of nonisothermal pixel in a narrow spectral region when we assumed that the radiometric temperature is invariable in the narrow spectral region. The derived equivalent temperatures in multi-spectral regions in 714―1250 cm?1 can characterize the change trend of nonisothermal pixel's radiometric temperature. 相似文献
Photosynthetically active radiation (PAR) is essential for plant photosynthesis and carbon cycle, and is also important for meteorological and environmental monitoring. To advance China’s disaster and environmental monitoring capabilities, the HJ-1A/B satellites have been placed in Earth orbit. One of their environmental monitoring objectives is the study of PAR. We simulated direct solar, scattered and environment radiation between 400 and 700 nm under different atmospheric parameters (solar zenith angle, atmospheric water vapor, atmospheric ozone, aerosol optical thickness, surface elevation and surface albedo), and then established a look-up table between these input parameters and PAR. Based on the look-up table, we used HJ-1A/B aerosol and surface albedo outputs to derive the corresponding PAR. Validation of inversed instantaneous and observed PAR values using HJ-1 Heihe experimental data had a root mean square error of 25.2 W m?2, with a relative error of 5.9%. The root mean square error for accumulated daily PAR and observed values was 0.49 MJ m?2, with a relative error of 3.5%. Our approach improved significantly the computational efficiency, compared with using directly radiation transfer equations. We also studied the sensitivity of various input parameters to photosynthetically active radiation, and found that solar zenith angle and atmospheric aerosols were sensitive PAR parameters. Surface albedo had some effect on PAR, but water vapor and ozone had minimal impact on PAR. 相似文献
A model for topographic correction and land surface reflectance estimation for optical remote sensing data in rugged terrian is presented.Considering a directional-directional reflectance that is used for direct solar irradiance correction and a hemispheric-directional reflectance that is used for atmospheric diffuse irradiance and terrain background reflected irradiance correction respectively,the directional reflectance-based model for topographic effects removing and land surface reflectance calculation is developed by deducing the directional reflectance with topographic effects and using a radiative transfer model.A canopy reflectance simulated by GOMS model and Landsat/TM raw data covering Jiangxi rugged area were taken to validate the performance of the model presented in the paper.The validation results show that the model presented here has a remarkable ability to correct topography and estimate land surface reflectance and also provides a technique method for sequently quantitative remote sensing application in terrain area. 相似文献
Based on light-use efficiency model, an MODIS-derived daily net primary production (NPP) model was developed. In this model, a new model for the fraction of photosynthetically active radiation absorbed by vegetation (FPAR) is developed based on leaf area index (LAI) and albedo parameters, and a pho- tosynthetically active radiation (PAR) is calculated from the combination of Bird's model with aerosol optical thickness and water vapor derived from cloud free MODIS images. These two models are inte- grated into our predicted NPP model, whose most parameters are retrieved from MODIS data. In order to validate our NPP model, the observed NPP in the Qianyanzhou station and the Changbai Mountains station are used to compare with our predicted NPP, showing that they are in good agreement. The NASA NPP products also have been downloaded and compared with the measurements, which shows that the NASA NPP products underestimated NPP in the Qianyanzhou station but overestimated in the Changbai Mountains station in 2004. 相似文献
The high spatial resolution and temporal observation frequency of HJ-1/CCD make it suitable for aerosol monitoring. However, because of the lack of a shortwave infrared band, it is difficult to use HJ-1/CCD imagery to retrieve aerosol optical depth (AOD). We developed a new algorithm for HJ-1/CCD AOD retrieval by introducing MODIS surface reflectance outputs (MOD09) as support. In this algorithm HJ-1/CCD blue band surface reflectance was retrieved through MOD09 blue band surface reflectance by band matching of the two sensors. AOD at 550 nm was then generated through a pre-calculated look-up table for HJ-1/CCD. Eighteen HJ-1/CCD images covering the Jing-Jin-Tang (Beijing-Tianjin-Tangshan) region were used to retrieve AOD using the new algorithm, and the AODs were then validated using AERONET ground measurements in Beijing and Xianghe. The validation shows that compared with AERONET ground measurements, 27/29 AODs have error less than 0.1 in absolute value.
Photosynthetically active radiation (PAR) is essential for plant photosynthesis and carbon cycle, and is also important for meteorological and environmental monitoring. To advance China’s disaster and environmental monitoring capabilities, the HJ-1A/B satellites have been placed in Earth orbit. One of their environmental monitoring objectives is the study of PAR. We simulated direct solar, scattered and environment radiation between 400 and 700 nm under different atmospheric parameters (solar zenith angle, atmospheric water vapor, atmospheric ozone, aerosol optical thickness, surface elevation and surface albedo), and then established a look-up table between these input parameters and PAR. Based on the look-up table, we used HJ-1A/B aerosol and surface albedo outputs to derive the corresponding PAR. Validation of inversed instantaneous and observed PAR values using HJ-1 Heihe experimental data had a root mean square error of 25.2 W m−2, with a relative error of 5.9%. The root mean square error for accumulated daily PAR and observed values was 0.49 MJ m−2, with a relative error of 3.5%. Our approach improved significantly the computational efficiency, compared with using directly radiation transfer equations. We also studied the sensitivity of various input parameters to photosynthetically active radiation, and found that solar zenith angle and atmospheric aerosols were sensitive PAR parameters. Surface albedo had some effect on PAR, but water vapor and ozone had minimal impact on PAR.
To satisfy the requirement of surface energy budget research on the meso-and micro-scale,a parameterization is developed to calculate high spatial resolution,clear-sky downward longwave radiation(DLR)from HJ-1B thermal data.The DLR algorithm is established based on extensive radiative transfer simulation and statistical analysis.To address the problem that HJ-1B has a single thermal channel and lacks atmospheric information,the brightness temperature of HJ-1B and water vapor content are used in the algorithm.An accuracy evaluation and error analysis for the algorithm is conducted using a simulated radiation dataset.The result shows that the algorithm performs well in most circumstances,but there is obvious underestimation when water vapor content is greater than 4g/cm2 .Error analysis indicates the accuracy of estimated DLRs is affected by uncertainties in input parameters,including water vapor content and top-of-atmosphere radiance.It is also affected by the difference between ground and near-surface air temperature.The algorithm is applied to actual HJ-1B data,and validated by ground data from six stations in the Heihe River and Haihe River basins.The estimated DLRs have good consistency with measured data except at Huazhaizi,and root mean square errors at most sites are around 20W/m2 ,which is slightly better than the result of MODIS. There is significant overestimation of DLR at Huazhaizi during summer,which is mainly produced by the large ground-air temperature difference.A correction process based on temperature difference is proposed and applied at Huazhaizi.The result shows that the positive bias is largely diminished after correction. 相似文献
