**5. Towards the implementation of a RnWebGIS**

The evolution of information technology and GIS allow a potentially unlimited number of users to access and manage geospatial information online [18, 19].

A WebGIS offers an efficient way to provide geospatial information and Web Services to concurrent users without installing a GIS. For this reason a WebGIS system is defined as a web information system that provides geographic information on the web through the Hypertext Transfer Protocol (HTTP) and the HyperText Markup Language (HTML) [17].

Therefore, a WebGIS is different from other web maps, such as Google Earth or Google Maps, since it integrates Internet/web technologies with functionalities of a GIS structure [7].

Fig. 10 shows a schematic diagram regarding the WebGIS architecture, with the following essential steps:


In the above-mentioned architecture the responsibility is on the server side, while the user (or client) needs only a browser in order to utilize the WebGIS and WebGIS applications. Therefore, the client sends requests to the GIS server which processes it and sends it to the client. Hence, the server performs the task of a *file server*, which contains the mapping data included in the WebGIS, while the client visualizes and consults the cartographic map. Therefore, the main elements of a WebGIS are the following: a) a web server, b) a scripting language, c) a database, d) a server mapping and e) an interface for the server mapping.

**Figure 10.** Schematic diagram of the WebGIS architecture.

In this paper, the RnWebGIS has been realized by using Open-source technologies, such as the *web server* Apache, a *MapServer* Project and the client interface *Pmapper*.

In the proposed RnWebGIS, the following databases have been included, such as:

	- **-** the provincial borders;
	- **-** the municipal boundaries;
	- **-** the urban center boundaries;

It is important to highlight that the obtained RnWebGIS allows the visualization of alphanumeric information associated with geographic features of interest, through the use of appropriate tables, or to implement the connection to other *web* pages or *database*, by using suitable *hyperlinks* functions.

16 Current Air Quality Issues

• first step: a user sends a request to the *web browser*;

information from the geographic databases;

**Figure 10.** Schematic diagram of the WebGIS architecture.

• administrative boundaries: **-** the provincial borders; **-** the municipal boundaries; **-** the urban center boundaries;

for the Rn concentrations.

district;

• second step: such a request is sent via Internet and processed by the server. Note that the WebGIS systems are equipped with a server mapping, such as *MapServer* [24] that obtains

In the above-mentioned architecture the responsibility is on the server side, while the user (or client) needs only a browser in order to utilize the WebGIS and WebGIS applications. Therefore, the client sends requests to the GIS server which processes it and sends it to the client. Hence, the server performs the task of a *file server*, which contains the mapping data included in the WebGIS, while the client visualizes and consults the cartographic map. Therefore, the main elements of a WebGIS are the following: a) a web server, b) a scripting language, c) a database, d) a server mapping and e) an interface for the server mapping.

In this paper, the RnWebGIS has been realized by using Open-source technologies, such as

• the Web Map Service (WMS), which allows to generate the satellite map of the Lecce

• the geostatistical results, which includes the prediction map of ICK and the level curves

the *web server* Apache, a *MapServer* Project and the client interface *Pmapper*.

• Rn concentrations and the related geographical information (Rn sites); • the cartographic maps of the permeability and the faults in Lecce district;

In the proposed RnWebGIS, the following databases have been included, such as:

• third step: the request is displayed to the user through the *web browser*.

Through specific queries on thematic maps, the user can display, in tabular form, the required data. For instance, by using the *identify* tool in the navigation bar, the user can obtain detailed information about the "Rn sites " layer as shown in Fig. 11.

**Figure 11.** Map Overlay functions: combining layers referred to administrative data, Rn concentrations sites and tectonic faults map. The identify tool highlights an example of Rn site (Collepasso municipality) with high Rn concentrations. Note that the red points indicate the sample locations and their size is proportional to the measured Rn concentration.

Another example of query is obtained by using the *search for* tool, in top left of the *p.mapper* Framework (version 4.1.1.) as shown in Fig. 12.

**Figure 12.** "Search for" tool with the visualization of the layer referred to "high" permeability overlapped on the "Rn site", "level curves of ICK" and "Prediction map of ICK" layers. The identify tool highlights two Rn sites (Collepasso and Copertino municipalities) with high Rn concentrations.

This function has been used to query the database associated with the layer "Permeability" and visualize, by using the thematic map, the study area with high level of permeability overlapped to the layers "level curves of ICK" and "Prediction map of ICK". In this case, the user can identify areas of high level of permeability close to area with high Rn concentrations.

Interactive navigation of maps is possible by using the tools implemented in the RnWebGIS, such as the use of *zooming/panning* available by selecting the object on the map.

On the other hand, in order to ensure the interoperability (i.e. exchange and/or sharing) of geographic data, it has been relevant to build a RnWebGIS according to the specifications of the services, defined by the *Open Geospatial Consortium* (OGC). Indeed, by using the features implemented in the RnWebGIS, the user can also integrate data located on different servers as well as data of different formats. This is possible by recalling the WMS given by the OGC that avoids duplication of data and, at the same time, provides updated geographical data which are certified by shared *standards*.

For example, it is worth highlighting that, by using the appropriate WMS, an orthophoto of Lecce district can be integrated with the layer "Prection map of OCK " as shown in Fig. 13.

**Figure 13.** Orthophoto of Lecce district, obtained by the WMS and integrated with the "Rn sites", "level curves of ICK" and "Prediction map of ICK" layers.

### **6. Conclusions**

In this paper, after introducing the usefulness of a GIS supported by geostatistical results, and reviewing some geostatistical modeling and predictions techniques used in the univariate and multivariate cases, a case study concerning a thorough geostatistical analysis of the Rn concentrations in soil gas over Lecce district has been discussed. In particular, four different spatial interpolation techniques, that is Ordinary Kriging, Log-normal Kriging, Cokriging with Indicator variable and Kriging with Varying Local Means, have been used in order to predict the Rn concentration levels over the study area. Then, an *ad hoc* WebGIS, called RnWebGIS, has been proposed. The map of the Rn predictions obtained by using Cokriging with Indicator variable, which performed more accurate predictions than the ones obtained by using the other methods, has been stored into the WebGIS, together with several

information about the geo-lithological features (such as permeability and tectonics maps), as well as administrative characteristics (such as demographic data and municipal boundaries) of the study area.

The proposed RnWebGIS highlights the usefulness of the integration between GIS and advanced geostatistical tools, in order to support the management of a sustainable development by taking into account even the risk of exposure to Rn pollution.
