# Towards a Digital Twin Prototype of Alpine Glaciers: Proposal for a Possible Theoretical Framework
## 3 DT Theoretical Framework
### DT at the Single Glacier Level
#### 3.1.2 Glacier Inventories  
The organization of the above mentioned amount of information within a structured database (DB) can follow some indications coming from the literature [21] that indicates how to enter and order data, how to plan for new data and the type of formats one has to adopt. The DB is expected to: (i) catalogue data at the glacier level; (ii) make data access and sharing possible, possibly enabling both upload and download of data themselves; and (ii) optimize data store and queries, possibly profiling communities of users. These DBs are named Glaciers Inventories. They mostly aim at the homogenization and synthesis of multi-source data providing operational information useful to describe glaciers and their dynamics over time. They could be intended as the skeleton of a DT where all the parameters/variables needed by models can be obtained. With a focus on the local level, and specifically considering the Italian Alps, the CGI has a unique, extensive history of glaciological documentation that, when combined with a spatially distributed and multi-temporal data, can provide an accurate, dynamic and complete reconstruction of recent glacier evolution, including one of the longest observation series of glacier frontal variations in the world [77]. One of the earliest glacier databases has been created by [PERSON] in 1925, listing 774 within the framework of initiatives promoted and supported by the CGI [79]. A more significant and innovative database, the Italian Glacier Inventory, was developed by the CGI in cooperation with the National Research Council (CNR) in the period 1959-1962. This database reports 838 glaciers covering a total area of about 500 km\({}^{2}\) developed through map analysis and field survey [71]. In the late 1970s, the CGI was part of the international team in the World Glacier Inventory (WGI), which was published in the late 1980s as a synthesis. Later, an update of the 1959 CGI-CNR Inventory was needed, and a photogrammetric campaign, supported by the Minister of the Environment, was operated to document all glaciers of the Italian Alps with dimensions greater than 0.05 km\({}^{2}\). The survey campaign, named 'Volo Italia 1988-1989\({}^{\prime}\), was able to identify 787 glaciers covering a total area of 474 km\({}^{2}\)[74]. In the period 2005-2011 a project called \"The New Italian Glacier Inventory\" was developed to fill the remaining gaps of the glacial inventory. It provided high-resolution colour orthophotos that were used to map 903 glaciers covering a total area of about 370 km\({}^{2}\)[80]. This new inventory was a breakthrough in the availability of glaciological data in the Italian Alps, providing an open-source availability of environmental data related to mountain regions. At the worldwide level, three inventories are globally recognized from scientific community: the WGI (World Glacier Inventory) [14], the GLIMS (Global Land Ice Measurement from Space) [20] and the RGI (Randolph Glacier Inventory) [13], providing all necessary elements for a detailed and accurate compilation of glacier inventory. The World Glacier Inventory (WGI) was established during the International Hydroological Decade (1965-74) with the aim of obtaining accurate assessment of the amount, distribution and variation of all snow and ice masses all over the world. The inventory includes information about more than 130,000 glaciers in terms of geographic location, area, length, orientation, elevation and classification. The WGI is primarily based on aerial photographs, and it represents a snapshot of the glacier distribution in the second half of the 20 th century. The WGI remains an important resource to understand the current state of global glaciers. In the 1980s, remote sensing techniques and automated processing were adopted to accelerate the inventory work, leading to the establishment of the Global Land Ice Measurement from Space (GLIMS) service.