# Validation of Regional-Scale Remote Sensing Products in China: From Site to Network
## 5 A National Validation Network and an Operational Validation System
### An Operational RSP Validation System  
As the last Component in Figure 1, a web-based land surface remote sensing product validation system (LAPVAS) is designed to use multi-scale in situ and remote sensing data for validating RSPs at regional and/or global scales. This system facilitates functionalities in data host and validation execution. The latter is performed based on single-point and multi-location comparisons in the case of homogenous and heterogeneous land surfaces, respectively. As shown in Figure 5, this system includes three key elements: (1) A validation database subsystem contains an original database that hosts ground measurements and, a validation data repository that stores the pixel scale reference data. Various analysis tools used to generate spatial-temporal scale matched validation data from \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Station** & **Core Site and Size** & **Location** & **Meteorology** & **Land Cover** & **Scientific Aims** \\ \hline \multirow{6}{*}{Huailiali Station} & East garden controlled experimental site & Prox: Hebei; & & & \\  & East garden controlled experimental site & Long: 115.783; & Precip: 650; & Type: Cropland; & Remote sensing mechanism; \\  & 100 m \(\times\) 100 m & Lat: 40.349; & Temp: 10 & LAI: 6.5 & Remote sensing mechanism; \\  & East garden & Long: 115.783; & Precip: 650; & Type: Cropland; & & \\  & 1.5 km \(\times\) 2 km & Lat: 40.349; & Temp: 10 & LAI: 6.5 & Remote sensing mechanism; ecological protection; crypt simulation model \\  & & EIE: 488 & & & \\ \cline{2-6}  & & Prox: Hebei; & & & \\  & Guanting reservoir & Long: 115.740; & Precip: 650; & Type: Water; & & \\  & 2 km \(\times\) 2 km & Lat: 40.352; & Temp: 9 & LAE: 0 & \\  & Ele: 475 & & & & \\ \hline \multirow{6}{*}{Jingyuetan Station} & Taipingpu controlled experimental site & Prox: Jilin; & & & \\  & 200 m \(\times\) 200 m & Long: 125.401; & Precip: 520; & Type: Cropland; & & \\  & & Lat: 43.998; & Temp: 4.4 & LAI: 4 & & \\  & 200 m \(\times\) 200 m & Ele: 211 & & & \\ \cline{2-6}  & Dehui corn & Prox: Jilin; & & & & \\  & Dehui corn & Long: 125.360; & Precip: 604; & Type: Cropland; & & \\  & 2 km \(\times\) 2 km & Lat: 41.19; & Temp: 4.8 & LAI: 5 & \\  & Ele: 207 & & & & \\ \hline \multirow{6}{*}{Hulumber Station} & Stipa bacialensis site & Prox: Inner & & & \\  & Stipa bacialensis site & Mongolia: & 120.087; & Precip: 380; & & \\  & 3 km \(\times\) 3 km & Lat: 49.342; & Temp: \(-\)1.0 & & \\  & Ele: 642 & & & & \\ \cline{2-6}  & & Prov: Inner & & & \\  & Cropland site & Mongolia: & 120.034; & Precip: 380; & & \\  & 3 km \(\times\) 3 km & Long: 120.036; & Temp: \(-\)1.0 & LAI: 4 & \\  & Ele: 49.308; & Ele: 638 & & & \\ \hline \hline \end{tabular}  
* Precip.: Annual averaged precipitation (mm); Temp.: Annual averaged temperature (°C); Prov.: Province;
* Long.: Longitude (°E); Lat.: Latitude (°N); Ele.: Elevation (m).  
\end{table} 
Table 2: Summary information of core observation stations in the validation network [169]. the original database are also included in this subsystem; (2) an RSP accuracy evaluation subsystem to quantify the uncertainties and consistency of a product, with accuracy, precision, completeness, spatial and temporal consistency, etc. are used as validation criteria; (3) an inter-external interface exchanges information among the validation database subsystem, the evaluation subsystem, and the RSP data flow. The original data in the validation database subsystem are collected from in situ measurements and/or from well-qualified high-resolution products for indirect validation purposes. The preprocessing of spatial scale transformation and temporal-scale matching are implemented to generate spatial-temporal matches among validation datasets and RSPs to be validated. The candidate RSP is preferred to be spatially and temporally consistent with reference data, which is processed by the inter-external interface to generate comparable data in the matched table (i.e., the data from candidate RSP and the counterparts from the validation data).