## 5 Conclusions  
This study was focused on the development of a methodology for rapid delimitation of built-up areas, based on Landsat satellite images, that are free of charge and offers global coverage and multi-temporal availability, free of charge. At the same time, one of the main objectives was to explore the possibilities of using such a model for the analysis of relatively large territories, characterized by a great variability in terms of land use/coverage, which causes a higher degree of difficulty in terms of analyzing territories based on the spectral response.  
According to the mentioned goals, we consider that we have fulfilled the proposed objective, developing a methodology with relatively good results, obtaining an overall validation score of over 85% for both all the images analyzed, and methods used. As the study presented, the methodology can be successfully applied in both urban and rural areas; moreover, it can be successfully applied in the areas where the territory is in full urbanization process, in which case the urban environment expands and intertwines with the rural environment.  
It is also worth mentioning that this type of analysis can provide fast mapping results for large areas, and due to the great temporal availability of Landsat satellite images, it can be used as a very useful tool for comparative analysis and evaluation of territorial dynamics from a multi-temporal perspective.  
The results clearly show that through such a methodology, based on a \"via negativa\" approach, it is possible to extract and map elements such as built-up areas, starting from the analysis of satellite images using vegetation indices and exploiting the lack of the presence of untargeted features.  
Towards the end, although this topic is frequently approached in the literature, the interest over time and the fact that the topic is still more than relevant, validates the importance of such studies. Therefore, we believe that this research makes a significant contribution to the field and aligns perfectly with similar scientific studies [36; 42; 45; 50; 65; 71; 72], adding value in terms of developing new practical tools for spatial analysis, management, and planning.  
As for the future work, this will involve further testing of the methodology presented, in multiple areas with various environmental conditions and different characteristics in terms of land use/land cover, aiming at a better calibration of the model and at the same time the improvement of the implementation capabilities for direct use as a tool in dedicated GIS software.  
Conceptualization, B.-E.D. and S.B.; methodology B.-E.D. and D.P.; software C.M. and B.-E.D.; validation S.R., B.-E.D. and S.B.; formal analysis I.V.; investigation B.-E.D. and S.B.; resources, I.V. and I.F. writing--original draft preparation B.-E.D. and S.R.; writing--review and editing B.-E.D. and S.R.; visualization B.-E.D. and C.M.; supervision D.P. and S.B. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The present work has received financial support through the project: Entrepreneurship for innovation through doctoral and postdoctoral research, POCU/360/6/13/123886 co-financed by the European Social Fund, through the Operational Program for Human Capital 2014-2020. All authors have an equal contribution to this paper. All authors contributed equally to this work.  
The authors declare that there are no conflicts of interest related to this article.