## 4 Example from the Heihe Station

Table 1: _Cont._
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Experimental Area** & **Validation Site** & **Alims, Validation Variables, and Scales** & **Observation Methods** & **Basic Information** \\ \hline Heihe Station Base & Dawhao controlled & Aims: Remote sensing mechanism, scale; Observation & AWS, Track crane & Precip: 110 mm; temp. : 7.8 \({}^{\circ}\)C; UUC: Copland, \\ (100.487e;3,8.835\"N, & experimental site & variables: Reflectance, emissivity, and brightness & ground-based remote & LAI: 5; science network: RSON; Prov. : Gansu; \\ 20,000 m\({}^{2}\)) & (100 m \(\sim\)150 m) & temperature measurements with multiple angles and polarizations; Scale: 1 m -30 m & sensing platform, WSN & Long: 100.372, Lat. 3856; Eie: 1524. \\ \hline \multirow{6}{*}{Babuo River Basin (2452 km\({}^{2}\))} & Abao River Basin & Alims: Hydrological model driving, validation; & AWS (5), SMTMS (5), AR & Precip: 270-670 mm; temp. 1.0 \({}^{\circ}\)C; UUC: Alpine \\  & Babuo River Basin (2452 km\({}^{2}\)) & Validation window: Snow depth, rainfall, LST, soil moisture, & AWS (5), SMTMS (5), AR & Precip: 270-670 mm; temp. 1.0 \({}^{\circ}\)C; UUC: CJPCS; UUC: C  
\begin{table} \begin{tabular}{l l l l l} \hline \hline
**Experimental Area** & **Validation Site** & **Aims, Validation Variables, and Scales** & **Observation Methods** & **Basic Information** \\ \hline Ejin Banner & & Aims: Ecological protection, HEM development, & \\ Natural Ossis & Sidagoia natural & validation, scale; & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & & \\  & & & \\  & & & & \\ \hline \hline \end{tabular}   
* AWS: Automatic weather station, including wind speed, air temperature and humidity, wind direction, air pressure, rainfall, snow depth, PAR, LST, and four components of radiation; SMTMS: Soil moisture and temperature measurement system, including temperature and moisture profile (6, the number of the sensors, same as below), heat flux (3), and average soil temperature (2); AR Superstation: A’rou Superstation, including wind speed(6), air temperature(6), humidity(6), wind direction, air pressure, PAR, LST, four components of radiation, rainfall, snow depth, soil moisture (20), soil temperature (30), soil temperature (7), Soil temperature (7), Soil temperature (8), Soil temperature (9), Soil temperature (10), Soil temperature (11), Soil temperature (12), Soil temperature (13), heat flux (3), and average soil temperature (14); SDQ Superstation, including wind speed (7), Air temperature (15), Soil temperature (16), Soil temperature (17  
Several pixel-scale validation sites involved in three remote sensing experimental areas based on HiWATER will be continuously maintained by the Heihe Station. One is the Babao River Basin, which includes three validation sites. The second is the Zhangye artificial oasis, which also includes three validation sites. The last is the Ejin Banner natural oasis, which is dominated by _Populuseuphratica_, Tamarix, and other arid region species. Some detailed information and instrumentation placement maps can be found in the introduction by [PERSON] _et al_. [23]. Table 2 shows the roles and the characteristics of the core remote sensing validation sites in the HRB. Figure 3 shows the distribution of these validation sites in the HRB. These validation sites were initially designed and established following the BigFoot Project's scheme. However, we use additional nested multi-scale observation systems (Figure 4). For example, the Daman farmland observation site includes observations on the kilometer scale (LAS, COSMOS), hundred-meter scale (EC) and meter scale (Lysimeter, WSN, and AWS), which can be used to validate evapotranspiration (ET) products at different scales [16]. These observations can also be used to analyze the scale effect and to develop a scale transformation method [24]. The scale effect and scale transformation in remote sensing product validation are still a great challenge in the long term.