# A GeoNode-Based Platform for an Effective Exploitation of Advanced DInSAR Measurements
## 3 GeoNode Platform  
As previously mentioned, the term \"Spatial Data Infrastructure\" is used to denote a relevant collection of technologies, policies and institutional arrangements that facilitate the availability of and the access to spatial data. In particular, a SDI is a framework for spatial data analysis and application for users and providers within all levels of government, the commercial sector, academia and by citizens  
Figure 3: TOPS mode Sentinel-1 amplitude image of Italy; the 250 Km swath extension is highlighted. in general. Moreover, we remark that a SDI eases the access to geographically-related information by using a minimum set of standard practices, protocols, and specifications [37]. The GeoNode, born as a project from the labs of the Global Facility for Disaster Reduction and Recovery of the World Bank, is a web-based platform providing an open source framework to implement a GIS and a SDI [43]. Because interoperability is a key concept for the implementation of an SDI, GeoNode is based on technologies compliant with the standards of the Open Geospatial Consortium (OGC), an international organization that makes open standards for the global geospatial community to improve sharing of the world's geospatial data [39]. In particular, GeoNode provides a complete environment with the following functionalities:  
* spatial search of the data and metadata;
* management and sharing of raster, vector data and metadata;
* management of security policies on data sharing;
* data visualization and integration from different sources, both stored on infrastructures and from services supplied from outside through the Web Map Service (WMS) [79], by using an integrated WebGis environment to build interactive maps. Moreover, we remark that GeoNode is written in the Python language [80] and leverages on well-known and robust Open Source products, which are summarized in the following:  
* DJango: a high-level Python Web framework [81], used to develop GeoNode;
* GeoServer: an open source software server written in Java [82] that allows users to share and edit geospatial data. Note that, by using open standards set forth by the Open Geospatial Consortium (OGC), GeoServer allows GeoNode for great flexibility in map creation and data sharing [83];
* pyCSW: an OGC CSW server [84] written in Python. Note that, in GeoNode, pyCSW provides a standards based metadata and catalogue component [85];
* GeoExplorer: a webGIS component for GeoNode [86];
* GeoWebCache: a Java web application used to cache map to accelerate and optimize map image delivery [87];
* PostgreSQL: an object-relational database, allowing efficient storage, query, and analysis of the location information [88];
* PostGIS: a spatial database extender for PostgreSQL object-relational database. It adds support for geographic objects allowing location queries to be run in the Structured Query Language (SQL), a standard language for storing, manipulating and retrieving data in databases [89]. In Figure 4, the interactions among the GeoNode core components is shown. GeoNode allows users to upload vector data and raster data. Vector data are uploaded in a PostgreSQL/PostGIS geodatabase as Shape Files, whereas satellite imagery and other kinds of raster data are retained as GeoTIFFs in the storage device of the file system. The uploaded data are then exported to the webGIS component of GeoNode, GeoExplorer, through GeoServer, by using GeoWebCache to accelerate and optimize the delivery of the map images. Moreover, Geoserver allows the access to PostgreSQL/PostGIS geodatabase, not only by using GeoExplorer, but also through other third part OGC compliant softwares, as for example QGIS [90] or arcGIS [91], to visualize and interact with the data. As soon as the upload is finished, the user can fill the metadata in order to allow an easy data searching and retrieval through the CSW (OGC Catalogue Service) by pyCSW.