1337 
SAMPLING METHODS USING REMOTE SENSING AND GLOBAL POSITIONING 
SYSTEM FOR CROP ACREAGE ESTIMATION AT - NATIONAL SCALE IN CHINA 
Quan Wu a , *, Li Sun a 
a CAAERP, Chinese Academy of Agricultural Engineering Research and Planning, 100125, No. 41 Maizidian Street 
Chaoyang District, Beijing 
- wuquan95@tom.com,- sunli0618@163.com 
Commission VII, WG VII/7 
KEY WORDS: Sampling, Sampling unit, Stratified sampling, RS, GPS, Agricultural condition, Acreage 
ABSTRACT: 
Sampling methods have to be applied in agricultural condition monitoring at national scale. When selecting sampling methods, more 
attention needs to be paid not only to objects monitored, but also to conditions monitoring such as money and time, etc. Stratified 
sampling method together with remote sensing has been successfully applied to main crops acreage monitoring for many years in 
China. Acting as the important complement for RS, ground sampling method system has been established in estimating main crop 
acreage. At a large enough scale, high efficiency and operability are key points in agricultural condition monitoring. Obviously, 
proper sampling methods have to be employed in agricultural condition monitoring using remote sensing at national scale because 
the total overcast investigation is not only unnecessary but also impossible. Thereby, it is very important to choose appropriate 
sampling methods and sampling methods need to be adapted to different tasks and crops. Crop acreage is very important information 
in agricultural condition monitoring using remote sensing or ground sampling methods. Stratified sampling using RS and ground 
random sampling methods are adopted by the Chinese RS Application Centre of Ministry of Agriculture in getting the acreage of 
winter wheat, com, soybean, rice and cotton. 
1. THE BACKGROUND 
1.1 Agricultural Condition 
Agricultural production is significant to any country, especially 
to China because of the great number of mral population. In 
2006, there were more than 470 million people among 900 
million country people working on farmland and the gross value 
of agricultural production was more than RMB 2400 billion. 
Therefore, it is of great importance for local and central 
governments to get accurate agricultural production information 
in time. Agricultural production information, which is called 
agricultural condition in China, includes some items as follows: 
1. Crop Acreage 
2. Crop Yield 
3. Natural Disaster (Flood, Drought, Insects, etc.) 
4. Growth condition 
Subject to the Ministry of Agricultural of China, Remote 
Sensing Applications Centre (RSAC) has been working on the 
above things as operating tasks and research projects for several 
years. In this article, methods for crop acreage estimation will 
be discussed. 
1.2 Crop Acreage 
Crop acreage, which means planting area of crop, is one of the 
most important agricultural condition information. Crop acreage 
is directly and closely related to crop’s total yield. Because crop 
yield per unit usually varies in the range estimated in normal 
year, crop acreage varies comparatively greater than crop yield 
per unit does, so is total yield, hence crop acreage information 
is even more important than crop yield per unit. There are many 
kinds of crops planted in China, but RSAC pays more attention 
to the main crops such as wheat, com, cotton, soybean and rice, 
etc. Due to the natural condition and planting habits, these crops 
are mainly centralized in about 15 provinces, but the planting 
time varies from province to province. Table 1 shows the 
planting regions and time for these main crops. For the purpose 
of getting these crops acreage data every year, RSAC has to 
select appropriate method to estimate. 
Crops 
Distributed area 
Planting time 
Spring wheat 
Northwest and 
Northeast China 
Mar.-Apr. 
Winter wheat 
Middle and East 
China 
Sep.- Oct. 
Com 
Northeast, Middle 
and East China 
Apr.- Jun. 
Cotton 
Northwest, Middle 
and East China 
Apr. 
Soybean 
Northeast,Middle, 
East China 
Apr. - May 
Rice 
Northeast, Southeast 
and South China 
Jan.-Mar., 
Jun.-Aug. 
Table 1. Crop planting area and time in China 
1.3 Methods of getting crops acreage data 
Generally, there are two ways of getting crops acreage data: one 
is from government statistics and the other is general survey 
* Corresponding author.