# GIS-Based Solar Radiation Mapping, Site Evaluation, and Potential Assessment: A Review
## 2 Solar Radiation Mapping Using GISs
### Solar Radiation Map as a Spatial DB  
There have been several studies that analyze the solar energy information in the area using the existing solar radiation map. These studies do not directly perform solar radiation mapping but use existing solar radiation maps to predict sunshine hours per year or to predict and compare regional solar radiation [5]. Some studies have compared the solar data extracted from the solar radiation map with the surface-measured data such as global horizontal irradiance (GHI), direct normal irradiance (DNI), diffuse horizontal irradiance (DHI), and the daily average clearness index to verify the accuracy and applicability of these solar radiation maps [6; 7]. The solar radiation maps constructed by various sources such as Solargis (Slovakia), the National Renewable Energy Laboratory (NREL) in the US, and the Energy Sector Management Assistance Program (ESMAP) of the World Bank are used as the spatial database of solar energy information. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**References** & **Usage or Method** & **Scale** & **Location** & **Used Data Type** & **Spatial Unit** & **Temporal Unit** \\ \hline [PERSON] and [PERSON] [5] & DB & National & Iran & Solar map & - & - \\ \hline [PERSON] and [PERSON] [6] & DB & National & Pakistan & Solar map & - & - \\ \hline [PERSON] and [PERSON] [7] & DB & Regional & Durban, South Africa & Solar map & - & - \\ \hline [PERSON] et al. [8] & DB & Regional & Korea (mines) & Solar map & - & - \\ \hline [PERSON] et al. [9] & DB & National & United Kingdom & Solar map & - & - \\ \hline [PERSON] et al. [10] & DB & Continental & Europe & Solar map & - & - \\ \hline [PERSON] and [PERSON] [11] & Multivariate relationship & Regional & Kamataka, India & Station measurement & Administrative district & Seasonal \\ \hline [PERSON] and [PERSON] [12] & Interpolation & National & Korea & Station measurement & Pixel & Monthly, Annual \\ \hline [PERSON] et al. [13] & Interpolation & National & Iran & Station measurement & Pixel & Monthly, Annual \\ \hline [PERSON] et al. [14] & Model validation & National & Pakistan & Satellite image, station measurement & Pixel & Annual \\ \hline [PERSON] et al. [15] & ANN 1 & National & Indonesia & Station measurement & Administrative district & Monthly \\ \hline [PERSON] et al. [16] & Advanced CRR 2 & National & Korea & Station measurement & Point & Monthly \\ \hline [PERSON] et al. [17] & Advanced CRR, Interpolation & National & Korea & Station measurement & Point, Pixel & Monthly \\ \hline [PERSON] et al. [18] & Advanced CRR, FEM 3  & National & Korea & Station measurement & Point, Pixel & Monthly \\ \hline [PERSON] and [PERSON] [19] & resun & Continental, National & Central and Eastern Europe, Slovakia & DEM 4, Various parameters & Pixel & Daily, Monthly, Annual \\ \hline [PERSON] and [PERSON] [20] & resun & Continental & Central and Eastern Europe & DEM, Various parameters & Pixel & Monthly \\ \hline [PERSON] and [PERSON] [21] & SOLARFLUX, ATM 5 & Regional & \begin{tabular}{c} Tefort Mountains and \\ Grand Canyon, US \\ \end{tabular} & DEM, Plant canopies & Pixel & Monthly \\ \hline [PERSON] [22] & Shadow analysis & Regional & \begin{tabular}{c} Mont Blanc Massif, \\ France \\ \end{tabular} & DEM & Pixel & 15 min intervals \\ \hline [PERSON] et al. [23] & Shadow analysis & Local & \begin{tabular}{c} The University of Lisbon, \\ Portugal (buildings) \\ \end{tabular} & \
\begin{tabular}{c} DSM 6, Station \\ measurement \\ \end{tabular} & Pixel &
\begin{tabular}{c} Hourly, Seasonal, \\ Annual \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of previous solar radiation mapping studies using GISs. Some studies were conducted for further analysis using solar radiation maps as DBs. The PV potential, power production, and economic effects can be estimated from a solar resource map using the software like RETScreen (Natural Resources Canada, Canada) shown in Figure 1[8]. In addition, the impact of climate change can be analyzed using the solar radiation map [9].