The paper introduces China Crop Watch System with Remote Sensing （CropWatch）

including its contents

technical innovation and operational development

validation and future activities. Crop Watch contents 5 components

consisting of crop condition monitoring

crop acreage estimation and yield prediction

grain production estimation

cropping index and crop structure monitoring

and drought monitoring. Each component is described briefly in this paper and detailed in following papers. Since 1998

the CropWatch has been put in operation. Each year

there are 7 monthly bulletins released

covering crop condition

crop acreage and yield

drought

agro-meteorology

cropping index and crop structure

and also grain production. And there are 21 10-days announcements released

covering drought and crop condition. During the operational period since 1998

the technology used by the CropWatch are consistently improved. All AVHRR image from 1991 are processed for calibration and correction precisely which began in 2000

including sensor calibration

zenith correction

cloudy detection and masking

geometric correction

atmospheric correction

BRDF correction

and NDVI and surface temperature calculation. The CropWatch uses both different image and growing profile of NDVI to monitor the crop condition

estimates crop acreage using remote sensing and sampling technique based on stratification. The cluster-sample framework is used to estimate plant proportion with TM and Radarsat image as samples

and transect-sampling framework is used to survey crop type proportion in planted-area. At the same time

The Crop Watch continuously expands its monitoring area. From 1998 to 2003

its monitoring area has been expanded from east China to national wide

to north and south America

to Australia and Thailand. Meanwhile

the Crop Watch continuously expands its monitoring contents

from crop condition monitoring

crop acreage estimation and crop yield prediction

to grain production

crop structure

and cropping index. The Crop Watch has its own validation programme. Each year

a few validation sites have been selected to do the field measurement for verifying specific results. For example

in 1999

Jiangning in South China were Dehui in North China were two sites. The crop LAI every 10 days and crop type proportion have been measured to verify the crop condition and crop acreage. Validation shows that the accuracy are up to 97% for plant proportion and 95 crop type proportion.