Relative Entropy (RE) is defined as the measure of degree of randomness of any geographical variable (i.e., urban growth). It is an effective indicator to evaluate the patterns of urban growth either compact or dispersed. In the present study RE has been used for evaluating the urban growth of Dehradun city. Dehradun, the capital of Uttarakhand is situated in the foothills of Himalayas, has undergone rapid urbanization. Landsat, Thematic Mapper (TM) satellite data of years 2000, 2010 and 2019 has been used in the study. Built-up cover outside municipal limits and within municipal limits was classified for the given time period. Road network and city centre of the study area were also delineated using satellite data. RE was calculated for period 2000–2010 and 2010–2019 with respect to the road network and city centre. High values of RE indicate higher levels of urban sprawl whereas lower values indicate compactness. Urban growth pattern over a period of 19 years was examined with the help of RE.
It was interesting to observe the growth patterns as characterized by the relative entropy. The results can provide many insights on the growth of this particular city.
Are you planning to apply this methodology to other cities? It would be interesting to see if cities from different regions or topography present distinct growth patterns, as well as to compare cities from different world regions. We found in a previous
study that world cities present similar topological properties (for the considered measurements):
https://www.researchgate.net/publication/320033522_Topological_characterization_of_world_cities
Also, it could be interesting to study how the adopted measurement relates to other geometrical features such as fractal dimension and lacunarity.
Regarding the delimitation of the are of interest in cities, we have developed a related methodology that can be of eventual interest for your developments:
https://www.researchgate.net/publication/303382033_A_diffusion-based_approach_to_obtaining_the_borders_of_urban_areas
Again, congratulations for the work.
All best wishes, Luciano da F. Costa
