*4.4. Credibility*

The final category can be considered as the most essential in operating terms and consists of four criteria: (1) calculation basis, referring to the theoretical background concerning each system's development; (2) output categorization, concerning the clarity and the relevance of the output to the fire danger rating; (3) validation, concerning the estimation of the system index values in real scenarios and based on the selected studies of this review; and (4) adaptability, related to the degree that a system has been successfully tested in different environments. In the first one, six cases can be distinguished: arbitrary, empirical, scientific-based systems, and their combinations per two. Arbitrary systems are considered less credible, especially in different environments; thus, no points are added in the evaluation process. Empirical systems are developed to be more well-suited to local conditions; hence, these systems are rated with two points, while the mixture of arbitrary-empirical basis is rated with one point. Scientific-based systems provide enhanced credibility; therefore, the respective rate equals three, the mixture of scientific-arbitrary basis is rated with two, and lastly, the mixture of scientific-empirical basis is rated with four, as it is the most complete approach. In the second one, the output categorization can be clear and immediately related to fire danger, moderately clear and related to fire danger, and not clear or not immediately related to fire danger, with ratings being 1, 0, and –1, respectively. In the third and the fourth criteria, the validation results and adaptability are rated from 0 concerning systems that have not been ye<sup>t</sup> deployed and from 3 concerning systems that have been used in almost every environment for a long period of time. The results of the evaluation procedure are displayed in Table 3. The results presented in Table 3 use the same weight for all criteria although the first and the last group are considered of higher importance as more criteria and points are included. Other combinations of weights can also be defined. NI, AI, KBD and NDVI are the top-performing indices, while IREPI, IBr, CWD, and DI have the lowest scores.


**Table 3.** The evaluation of systems and indices for fire danger rating.

S4

 Credibility  G Fire danger aspect

**Table 3.** *Cont.*


 M

Meteorology

 E  Empirical


**Table 3.** *Cont.*
