# Geovisualization Techniques of Spatial Environmental Data Using Different Visualization Tools
## 3 Results of Visualization
### Evaluation of Nitrate and Phosphate Distribution in 2013 and 2019  
The concentration of PO43 in the reference year before the construction of the sewage system indicated severe contamination. In 65% of the wells we measured a concentration higher than the contamination limit of 0.5 mg/L. Having investigated the spatial distribution it can be concluded that the majority of the settlement is contaminated, the highest concentration of phosphate was measured in the central areas of the settlement (2 mg/L), with a decreasing trend towards the Northern and Southern parts of the settlement.  
In the year 2019 significant changes could be observed. We measured a concentration above the limit value in only 32.5% of the wells, compared to 2013 when the same value was 65%. The maximum value of 4.07 mg/L measured in 2013 had decreased to 2.14 by 2019. The central part of the settlement is still considered the most contaminated part; however, in this year there was no area with a concentration above 2 or 3 mg/L, and only a small area where the concentration exceeded the value of 1.5 mg/L. The other important change was the significant increase in the extension of the areas which can be characterized by a concentration under the limit value. Whereas in 2013 we measured a concentration under the limit value only in the Northern and Southern peripheral areas of the settlement, in 2019, we measured concentrations under the limit value, except in the central area of the settlement and some smaller regions.  
In 2013, before the construction of the sewage system, we measured concentrations above the limit value of 50 mg/L in 75% of the wells. Furthermore, in the reference year before the construction of the sewage system we found a characteristic spatial distribution. The Southern parts of the settlement showed a significant degree of contamination. From the central part of the settlement towards the Southern direction we measured concentrations above 200 mg/L, and in a coadjacent area, we measured concentrations above 300 mg/L. In contrast, the Northern part of the settlement was less contaminated; however, in the majority of the area we still measured concentrations above the contamination limit of 50 mg/L.  
In 2019, the fifth year following the construction of the sewage system, the decrease in the concentration of NO3- also indicates the elimination of a significant part of the contaminant supply, since the average value decreased from 187.8 mg/L to 163.5 mg/L from 2013 to 2019. The value of the lower quartile decreased from 50.15 mg/L to 43.09 mg/L from 2013 to 2019, while the value of the upper quartile decreased from 341.7 mg/L to 244.8 mg/L. By 2019 the North-South difference had been eliminated, and significant positive changes occurred in the central parts of the settlement. The most contaminated areas were still the Southwestern and Southeastern parts of the settlement, even though their extension had significantly decreased (Table 2).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Tool**} \\ \cline{2-5}
**Viewpoint** & & & **QGIS Module** & \\ \cline{2-5}  & **KML** & _qgis2 web_ & _Cloud_ & _Qgis2 threejs_ \\ \hline
**Appearance** & 2D and 3D & 2D & 2D & 3D \\ \hline
**Supported raster format** & Yes & Yes & No & Yes \\ \hline
**Browser needs plugin** & No & No & No & Yes \\ \hline
**Event management** & Supported & Supported & Supported & Supported \\ \hline
**Require coding** & Yes & No & No & No \\ \hline  & Up to 10,000 lines, shapes, & & & \\  & or places & & & \\
**Feature/Data Limit** & Up to 50,000 total points & Depends on & 50 MB upload & Depends on \\  & (in lines and shapes) & hardware & data limit & hardware \\  & Up to 20,000 data table cells & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Evaluation of tools.