China is a large agricultural country. To understand the agricultural production condition timely and accurately is related
to government decision-making, agricultural production management and the general public concern. China Agriculture
Remote Sensing Monitoring System (CHARMS) can monitor crop acreage changes, crop growing condition, agriculture
disaster (drought, floods, frost damage, pest etc.) and predict crop yield etc. quickly and timely. The basic principles,
methods and regular operation of crop growing condition monitoring in CHARMS are introduced in detail in the paper.
CHARMS can monitor crop growing condition of wheat, corn, cotton, soybean and paddy rice with MODIS data. An
improved NDVI difference model was used in crop growing condition monitoring in CHARMS. Firstly, MODIS data of
every day were received and processed, and the max NDVI values of every fifteen days of main crop were generated,
then, in order to assessment a certain crop growing condition in certain period (every fifteen days, mostly), the system
compare the remote sensing index data (NDVI) of a certain period with the data of the period in the history (last five
year, mostly), the difference between NDVI can indicate the spatial difference of crop growing condition at a certain
period. Moreover, Meteorological data of temperature, precipitation and sunshine etc. as well as the field investigation
data of 200 network counties were used to modify the models parameters. Last, crop growing condition was assessment
at four different scales of counties, provinces, main producing areas and nation and spatial distribution maps of crop
growing condition were also created.