Retrieval of Normalized Difference Vegetation Index（NDVI）with high spatial and temporal resolutions from remote-sensing data is important for monitoring the dynamic changes in vegetation. However

owing to the impact of weather

a single satellite cannot provide a time series with high-spatial-resolution NDVI data. An effective solution to this problem is to fuse the NDVI with various resolutions retrieved from different sensor data to produce a dataset that has both high spatial and high temporal resolutions. In this study

the middle east part of North China Plain is selected as the experiment area

and HJ-1 CCD and MODIS NDVI data are used. The spatial and temporal adaptive reflectance fusion model is improved in two ways:（1）The difference of the spectral responses between different objects is considered-using the confidence interval（ x ±2σ） to filter the data and consequently reduce classification errors

and the linear regression method is used to modify the spectral distance weight according to different objects.（2） The predicted radius is defined to predict the missing HJ-1satellite data whose unavailability is caused by external influences. Results indicate that the distribution of high and low NDVI values of the six studied dates is highly consistent between the observed and predicted images. According to the results of the correlation analysis

the scatter points concentrate along the line of y=x. The correlation coefficients of the six pairs of observed and predicted NDVI images are 0.957

0.962

0.935

0.964

0.913

and 0.933

which are all significant at 0.01 levels

and all RMSEs are less than 0.07

which indicates good fusion results. According to the difference images and their histograms

the averages of the six difference images are-0.02

0.001

-0.012

-0.025

0.023

and-0.02

with standard deviations of 0.049

0.044

0.049

0.036

0.056 and 0.043

respectively. The pixel values concentrate around 0

and 90% of the pixels have absolute values smaller than 0.1. The percentages of pixels that have absolute values smaller than 0.2 are 99.80%

99.97%

99.95%

99.98%

99.79%

and 100%for the six images. The accuracy of results tends to decrease as the time intervals increase between the base and prediction dates. The comparison of the results of IR shows that the prediction accuracy of the improved algorithm is higher than that of the original algorithm. The results also show that the base and predicted images have similar seasonal characteristic. If the time interval is extremely long

however

similar seasonal characteristics are not obvious or exhibit significant differences

which reduce the accuracy and precision of the prediction results. Therefore

an appropriate reference image should be selected. In summary

the improved method is employed to reconstruct NDVIs with high temporal and high spatial resolutions by combining the spatial details of HJ-1 CCD data and the temporal variation of MODIS data to effectively supplement the missing HJ-1 CCD NDVI dataset.