# Scaling of FAPAR from the Field to the Satellite
## 2 Study Area and Data
### Measurement and Data Preparation
#### 2.2.1 _In-situ_ Measurement  
To guarantee their representativeness to the study area, the _in-situ_ sites were configured following a mean of surfaces with non-homogeneity (MSN) sampling strategy, which considers the autocorrelation and stratified non-homogeneity of the area using a fine-resolution classification map [34; 35]. Thirteen cornfield sites were distributed throughout the area almost uniformly (Figure 1) within an extent of \(5\times 5\) km. From 24 May to 10 July 2012, canopy structural parameters and FAPAR  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Categories** & **Temporal Info.** & **Spatial Info.** & **Description** \\ \hline \multirow{3}{*}{\begin{tabular}{c} _In-situ_ \\ measurement \\ \end{tabular} } & \multirow{3}{*}{30 May 2012–18 July 2012} & \multirow{3}{*}{13 sites} & Mobile measurement for 12 sites at & approximate 5-day intervals and \\  & & & continuous stationary measurement \\  & & & for the left 1 site \\ \hline \multirow{3}{*}{MODIS FAPAR} & 24 May 2012–10 July 2012 at 8-day intervals & \multirow{3}{*}{\
\begin{tabular}{c} scene h25v05 at 1 \\ km resolution \\ \end{tabular} } & \multirow{3}{*}{MOD15A2 C5; ISIN projection} \\  & 30 May 2012, 15 June 2012, & & \\  & 24 June 2012, 10 July 2012 & & \\ \hline SPOT-5 image & 10 August 2008 & 10 m resolution & Ancillary for geometric registration \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Land cover \\ classification \\ \end{tabular} } & \multirow{3}{*}{25 June 2012} & \multirow{3}{*}{1 m resolution} & Ancillary for geometric registration \\ \cline{1-1} \cline{3-3}  & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Data used in the presented study.  
Figure 1: Map of study area and field measured sites.  
values were measured repeatedly every five days. The field measurement has been interrupted from 18 June to 3 July by bad weather and irrigation schedule, leaving a data gap during the period. Canopy structural parameters include the average canopy height, leaf numbers, plant density and LAI _etc._ The canopy FAPAR values were measured by the AccuPAR LP-80 Ceptometer ([[http://www.decagon.com](http://www.decagon.com)]([http://www.decagon.com](http://www.decagon.com))) and four values were acquired at each measurement: the incident PAR above the canopy (PAR\({}_{\text{a}}^{\dagger}\)), reflected PAR above the canopy (PAR\({}_{\text{a}}^{\dagger}\)), incident PAR below the canopy (PAR\({}_{\text{b}}^{\dagger}\)) and reflected PAR by ground (PAR\({}_{\text{b}}^{\dagger}\)). According to the device instructions [2; 36], the canopy FAPAR can be calculated by  
\[\text{FAPAR}=(\text{PAR}_{\text{a}}^{\dagger}-\text{PAR}_{\text{a}}^{\dagger} -\text{PAR}_{\text{b}}^{\dagger}+\text{PAR}_{\text{b}}^{\dagger})/\text{PAR} _{\text{a}}^{\dagger} \tag{1}\]  
At each site, a 10 m \(\times\) 10 m sample plot was enclosed and measurements were made 8 to 10 times along the diagonal of the sample plot repeatedly and continuously in a short time. To reduce the measurement errors affected by the spatial representativeness of instrument, operator-dependent errors and changing weather conditions (such as cloud or wind), an averaged FAPAR was calculated from the repeated measurements as the value representative for the plot. Details of the _in-situ_ dataset could be referred to [37].