GVG instrument is an integration of video capture card

GPS receiver and GIS for collecting the crop type proportions in the field. VIDEO and GPS are integrated into the GIS installed in a notebook. GVG mounted on car or motor takes records with video camera during the movement. The car should not be fast than 40 km/h in order to acquire high quality of pictures. When GVG is working

it records pictures and the position from GPS as well as geographical attributes from GIS data layer

for example county code

into a temporarily database. One person is enough to operate GVG in addition the driver. When fieldwork is done

the GVG provides the function to review every pictures recorded during the sampling. If the picture does not contain the arable land

it shall be discarded

otherwise

the proportion of every crop types will be recorded manually

and the picture will be recorded too. Once all pictures are reviewed for a transect line

it is easy to calculate the proportion of crop types. The crop proportions for a county can be calculated from all transect lines within the county

and the same for stratum. GVG has been used to obtain the crop type proportions of entire country since 1999. The extensive validation shows the GVG can have the accuracy of 95% for main crops

including wheat

rice

maize and soybean. According to the principle of GVG

it has multi-purpose applications

not only on the crop type proportions

but also on environment monitoring for example.