通过在实验区内设置不同类型的采样线,对GVG采样线的代表性进行检验.结果表明,高速公路和乡村道路类型的采样线对区域代表性的精度在95%以上;国道为86.726%;省道为65.447%.对于不同的缓冲区,高速公路、省道和乡村道路类型采样线,以200m缓冲区的代表性最好.而国道则以800m缓冲区的代表性最好.对于不同的作物而言,无论何种类型的采样线或者缓冲区,种植面积最大的棉花的精度是最好的.最低的是省道采样线1000m缓冲区,精度是78.146%,最好的是国道采样线800m缓冲区,精度是99.974%.除省道外,其他精度都在94.8%以上.这说明GVG采样线所获得的成数对于区域主要作物的代表性是很好的.

The GVG crop sampling instrument is an integration system based onGIS, and ismade up ofGPS receiver,Video capturing. Ithas been applied in the field of the crop yield estmi ationwidely. The authors verified accuracy of the representative of theGVG sampling lines in a testgroundwith an area of5km×5km inGong anCounty, HubeiProvince.Themap of land plot in the expermi ent area was drawn out based on land use map and high resolution satellite mi age-SPOT5. The crop area proportion of each land plotwas investigated andmarked on themap of the land plot, and\nthen the true proportions of the crop in the expermi entareawereworked out. Four types of the sampling lineswere setup in the expermi entarea. Theywere freeway, national road, provincial road and countryside road. TheGVG instrumentwas used to sample the cropsbased on the sampling lines, and then the crop proportion ofGVG were obtained. The buffers of 200m, 500m, 800m, and 1000m of each sampling line were set up and the true crop proportion of the buffers were obtained based on GIS. The representative of the sampling lines was verified by comparing the true values with the expermi ental values.The results showed that the sampling lines of freeway and countryside road had the bestaccuracy greater than 95%,the national road took the second placewith an accuracy of86.726%, and the provincial roadwas theworstwith an accu- racy of65.447%.Among all the buffers, the 200m-buffersofthe freeway, provincial road and countryside road had the bestrepresenta-tive, and itmatched the buffer of100—200m aswe designed the GVG system. But the best of the national road is the 800m-buffer.As fordifferentcrops, nomatterwhat type the sampling line orbuffer is, the accuracy of the cottonwas the best, the lowestwas the 1000m-buffer at the type of the provincial road sampling linewith the accuracy of78.146%,and the best was the 800m-buffer ofnational roadwith the accuracy of99. 974%. All the accuracies of the sampling lineswere over 94.8%, except the provincial road. It showed that the GVG instrument has a very good representative for the dominant\ncrop-cottonwhich had the highest accuracy to each buffer in every sampling line.