It is the first identification of the green infrastructure of Barcelona from the NVDI index. On the one hand quantifies the real green of Barcelona and characterizes its distribution in relation to different administrative and urban parameters that help to understand possible territorial deficiencies and find instruments to amend them. On the other hand, it proposes to generate a database of green infrastructure of the city, which serves to provide it with contents, functions and environmental services that it performs.
The methodology for calculating the NDVI index in the city of Barcelona and its characterization in relation to territorial, administrative and urban parameters has three distinct parts:
• First, an NDVI orthophoto with 40 cm of Resolution, based on a photogrammetric flight that has covered the whole municipality of Barcelona with a pixel size on the ground of 9 cm. The NVDI index is calculated as follows:
(Reflectivity to the near infrared region - Reflectivity to the red region) / (Reflectivity to the near infrared region + Reflectivity of the red)
External orientations have been corrected by adjusting the NDVI index to digital models of surfaces obtained from correlation techniques and with crowns of trees projected to the ground.
• Secondly, the information has been validated in several control areas of the city and the exact limit of detection of green has been established without detecting other non-vegetated areas. The error has also been evaluated proving the correlation with the positioning of the trees and the digital altitudes model.
• Finally, 1:10.000 scale maps of the distribution of the green and the NVDI index have been generated to the whole city (see maps A0 +) and the index has been analyzed crossing it with that of the districts, neighborhoods, population and qualifications, in order to characterize their administrative and urbanistic territorial distribution.
It should be noted that the data provided by the NDVI are related to the green coverage, i.e. the green surface seen from the sky. In this way, for example, the whole canopy of a tree, regardless of whether it covers constructed or paved surfaces, is considered as green surface. Thus, the NVDI does not provide information on the structure and complexity of this green, and can not be confused with the green treading surface. On the other hand, despite being the best possible approximation to the city's vegetation, in the calculation of the NVDI index, some serious error is observed in narrow streets, in addition to a lack of detection of the green in some deciduous tree species in Points of the city where the flight occurred in April-May and leaves had not yet grown.
The aerial images taken on Barcelona for the calculation of the NDVI are of different dates (April, May, June9) and this generates some problem of homogeneous treatment of the data. However, the approximation level of the green is very precise as seen in the two control points analyzed and gives us very valuable information about the green coverage of the city.
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Checked: March 20, 2019