All information from: http://senseable.mit.edu/treepedia
Using the Green View Index

The Green View Index (GVI) was calculated using Google Street View (GSV) panoramas. This method considers the obstruction of tree canopies and classifies the images accordingly. By using GSV rather than satellite imagery, we represent human perception of the environment from the street level. The GVI presented here is on a scale of 0-100, showing the percentage of canopy coverage of a particular location. Explore the maps above to see how the GVI changes across a city, and how it compares across cities and continents.
Publication
X Li, C Zhang, W Li, R Ricard, Q Meng, W Zhang (2015). Assessing street-level urban greenery using Google Street View and a modified green view index. Urban Forestry & Urban Greening 14 (3), 675-685
I Seiferling, N Naikc, C Ratti, R Proulx (2017). Green streets − Quantifying and mapping urban trees with street-level imagery and computer vision. Landscape and Urban Planning 165: 93–101
X Li, C Ratti (2018). Mapping the spatial distribution of shade provision of street trees in Boston using Google Street View panoramas. Urban Forestry & Urban Greening 31: 109-119