# Towards a Digital Twin Prototype of Alpine Glaciers: Proposal for a Possible Theoretical Framework
## 3 DT Theoretical Framework
### DT at the Single Glacier Level
#### 3.1.1 Basic (Gaciological) Data  
According to [76] (see also Figure 5), a **basic description** of a glacier can be obtained with reference to three types of information: (i) basic information (ii) in situ data, i.e., measures collected during glaciological campaigns; and (iii) historical documentations.  
From a physical asset point of view, each glacier inventory is a target point relying on data collection from both traditional surveying methods and, nowadays, EO data.  
As far as **basic information** is concerned, the following information has to be obtained: (i) glacier identification through the adoption of a proper unique code and/or name; (ii) glacier type; (iii) glacier location and local topography/orography; (iv) administrative data, permitting the association of the glacier to the closest/more proper administrative unit (county, province, region, country); (v) glacier position with respect to a proper coordinate reference system; (vi) technical data about the basin hosting the glacier and its eventual relationship with neighbour basins possibly reaching the sea; (vii) orographic classification of the area according to both the \"Traditional\" and the \"Suddivisione Orografica Internazionale Unificata del Sistema Alpino\" (International Standardized Mountain Subdivision of the Alps, SOIUSA) systems [78]; (viii) morphological characterization, including body shape, frontal characteristics and longitudinal profile of the glacier; and (ix) morphometric features such as glacier size (m\({}^{2}\)), elevation (max, min, mean and median; m a.s.l.), thickness (m) and mean/max length (m).  
It has to be pointed out that measures have always to be associated with the date of the survey in terms of day, month and year. This enables multi-temporal comparison of the glacier's condition.  
As far as **in situ data** are concerned, the following ones are desirable: (i) direct measures obtained from reference signs, (ii) photographic stations installed close to the glacier from fixed and stable points, and (iii) wherever possible, some geomorphology observations in order to know the \"health state\" of glaciers. In Italy, these measures generally come from glaciological campaigns (past and current) performed by the CGI  
Figure 5: Digital Twin theoretical framework at the single glacier level.  
(Italian Glaciological Committee) and refer to the glacier terminus and mass. New measures from successive campaigns are expected to enable the assessment of geomorphological changes over time.  
Finally, considering the **historical data**, information can be grouped into two main classes: (i) text documents that report the general conditions of the glaciers, the main observed changes, the eventual occurrence of relevant phenomena (e.g., rockfall, lake growth/reduction, etc.). Documents can also correspond to pictures (including terrestrial and aerial photos), cartographic data stored in digital files, articles of journals, books, and unpublished studies; (ii) Topographic surveys and technical/thematic maps.  
Auxiliary parameters, supporting and completing the basic ones, mainly concern the presence (or not) of the glacier at the time of the inventory, and eventually associated local codes and alternative glacier classification relying on local criteria.