# Measuring international cities’ tree canopy

# International Comparison Documentation

This page attempts to show how the international comparison was performed, using Vienna as an example.

The first step is to get a 20km by 20km radius around the city of choice, for logistical reasons this is a square.

We then need to find where the water is as to not disrupt the estimates with zeros.

After finding where the water is, we need to then cut up the city into a grid, each 1km by 1km. This gives us 400 ‘chunks’ to perform the analysis. Now we take a look at an example grid square.

First, find the bonding box for each grid square.

Then we subtract the water layer.

Then, we find the tree coverage for that square, excluding water. We can then calculate a simple percentage covering of the grid square.

Then we get our final answer of 0.3154. We then repeat for all 400 grid items, and then save the results to a file for later analysis.