The relationship of NDVI and GVI, and the effect of building heights: A case study in Athens, Greece

Urban green spaces play a crucial role in enhancing the sustainability of cities, making it a necessity for their measurement methods to be precise and reliable. Mapping of urban green has been standardized with multiple data sources, such as the Normalized Difference Vegetation Index (NDVI) derived from satellite imagery, and the Green View Index (GVI), derived from street-level imagery. Both are popular, complementary methods for quantifying urban green. This case study, in Athens, Greece, aims to investigate the strength of their relationship for different resolutions of NDVI. In addition, as NDVI is sensitive to height variations of the imaged area, this relationship was also quantified in terms of the effect of building heights. Results show a strong relationship between the two indices, but not linear. Incorporating building heights into proper models is a method that could support a more comprehensive approach.