Quantifying greenness of cities with satellite imagery and AI

Urban green spaces in Amsterdam segmented with 10m resolution Sentinel-2 images
Urban green spaces in Amsterdam segmented with 10m resolution Sentinel-2 images

An ever-growing scarcity of natural resources, climate change with increasing temperatures, droughts and floods, and a growing world population put cities under pressure. With cities growing exponentially larger and more people living, working and commuting within those cities green spaces are often the first to go.

With the changing climate, we face more frequent and more severe heatwaves. Green spaces can help to cool the city. The difference between a street with trees and a street without trees is very noticeable. Urban green spaces also help to capture stormwater and preserve biodiversity. The health and social benefits of urban green spaces have been discussed widely as well.

Benefits of Urban Trees (Source: The Nature Conservancy)
Benefits of Urban Trees (Source: The Nature Conservancy)

To help raise awareness and to help policymakers data is needed to improve decision making. To do this at a global scale, Husqvarna and 20tree.ai worked closely together to launch HUGSI. HUGSI is short of Husqvarna Urban Green Space Index and unveils insights about the size, distribution and health of green spaces in urban areas of 98 cities across 51 countries.

Within 3 months, from kick-off to launch, a dedicated team from both companies worked side-by-side to achieve this result. The teams consisted of a complementary set of talented people. Husqvarna’s expertise in green space management and 20tree.ai’s expertise in applying machine learning to satellite imagery proved to be a perfect match. The scale that we wanted to roll out the solution was unmatched. Green spaces in different cities have been compared in different studies, but often traditional remote sensing techniques have been used, for example, a simple NDVI threshold or simpeler methods like Random Forests. These show well-known shortcomings in terms of generalisability and accuracy.

HUGSI.green ranking
HUGSI.green ranking

That’s were 20tree.ai’s expertise in deep learning comes in. From the beginning, it was clear that a thorough machine learning set-up and validation scheme was needed to make sure that the results were reliable and scalable with 10m resolution Copernicus Sentinel-2 imagery. Ordering higher resolution satellite imagery, for example, 30cm or 1.5m resolution, was not scalable in terms of costs and availability.

With a limited training set, consisting of high-resolution labels of trees, low vegetation and grass, water and other, we had to train a deep learning segmentation algorithm to classify land-use at a global scale with 10m resolution. We needed to make sure that vegetation in different geographical areas, from Gothenburg to Dubai and Hong Kong is classified correctly. Therefore, we decided to keep the most challenging cities as a validation set, ensuring the generalisability of the algorithms.

Access to green spaces in and around São Paulo (Brazil) is not equally distributed

During the process, we’ve experimented with different segmentation algorithms. The beauty of satellite imagery is that it contains more bands than the visible RGB. Especially, Sentinel-2 with 12 bands, from Ultra blue to Visible and Near Infrared (VNIR) and Short Wave Infrared (SWIR) is extremely useful for analysing vegetation.

HUGSI is just the beginning. Husqvarna and 20tree.ai are committed to continuously extend and evolve our joint offerings. For municipalities, we provide more detailed analysis, that can include insights on tree level. For example, to assess biodiversity and changes over time.

Land-use classification Austin (USA)
Land-use classification Austin (USA)

How does your city rank on HUGSI.green? Do the numbers match your expectations?

Thanks to David de Meij.

 

COOKIE POLICY

This website of Overstory B.V. (the “Owner”), which is available at https://www.overstory.ai/ (the “Website”), uses Cookies and similar technologies in order to ensure the correct functioning of its services and to improve the navigation experience of the users. This document provides detailed information regarding the use of Cookies and similar technologies and how they are used in the Website.

What are Cookies?

Cookies are text files containing small amounts of information that are downloaded to your device when you visit a website. Cookies are then sent back to the originating web domain on your subsequent visits to that domain. Most web pages contain elements from multiple web domains so when you visit the website, your browser may receive cookies from several sources.

Cookies are useful because they allow a website to recognise a user’s device, allowing you to navigate between pages efficiently and to remember preferences and generally improve the user experience.

Session cookies are deleted automatically when you close your browser and persistent cookies remain on your device after the browser is closed (for example to remember your user preferences when you return to the Website).

For further information, please visit http://www.allaboutcookies.org/

What categories of Cookies are used by the Website?

The Cookies used on the Website are described hereinafter:

  • Strictly necessary Cookies
    This Website uses Cookies to save the User’s session and to carry out other activities that are strictly necessary for the operation of this Website, for example in relation to the distribution of traffic. These cookies are essential in order to enable you to move around the Website and use its features.
  • Performance Cookies
    This Website uses Cookies to save browsing preferences and to optimise the User’s browsing experience. Among these Cookies are, for example, those used for the setting of language or for the management of first party statistics employed directly by the Owner of the Website.
    The services contained in this section enable the Owner to monitor and analyse web traffic and can be used to keep track of User behaviour. This allows us to provide a high quality experience by customising our offering and quickly identifying and fixing any issues that arise.
    Some of the services listed below collect statistics in an anonymised and aggregated form and may not require the consent of the User or may be managed directly by the Owner – depending on how they are described – without the help of third parties.
    If any third party operated services are listed among the tools below, these may be used to track Users’ browsing habits – in addition to the information specified herein and without the Owner’s knowledge. Please refer to the privacy policy of the listed services for detailed information.
 Cookie Name Source Purpose Further Information

-utma

-utmb

-utmc

-utmz

_hp2_ses_props.APP_ID

_hp2_props.APP_ID:

 

 

 

 
Google Analytics

Google uses the data collected to track and examine the use of this Website (e.g. how visitors use the Website), to prepare reports on its activities and share them with other Google services.

Google may use the data collected to contextualise and personalise the ads of its own advertising network.

Stores timestamp and cookie domain/path

Stores properties set by addEventProperties API)

Google Analytics is a web analysis service provided by Google LLC (“Google”).

Personal Data collected: Cookies and Usage Data.

Place of processing: United States – Privacy PolicyOpt Out; Ireland – Privacy Policy. Privacy Shield participant.

Click here for Google’s privacy policy in respect of Google Analytics http://www.google.com/analytics/learn/privacy.html

You may opt out of tracking by Google Analytics by visiting https://tools.google.com/dlpage/gaoptout?hl=en-GB.

 
  • Managing contacts and sending messages Cookies
    This type of cookies makes it possible to manage a database of email contacts, phone contacts or any other contact information to communicate with the User. These services may also collect data concerning the date and time when the message was viewed by the User, as well as when the User interacted with it, such as by clicking on links included in the message.

How you can provide or withdraw consent to the installation of Cookies?

Some of the purposes for which Cookies are installed may also require the User’s consent. You will have seen a pop up to this effect on your first visit to this website. Although it will not usually appear on subsequent visits, you may withdraw your consent at any time by following the instructions set below.

Where the installation of Cookies is based on consent, such consent can be freely withdrawn at any time following the instructions provided in this document.

In addition to what is specified in this document, you can manage preferences for Cookies directly from within your own browser and prevent – for example – third parties from installing Cookies.

Through browser preferences, it is also possible to delete Cookies installed in the past, including the Cookies that may have saved the initial consent for the installation of Cookies by this website.

Users can, for example, find information about how to manage Cookies in the most commonly used browsers at the following addresses: Google Chrome, Mozilla Firefox, Apple Safari and Microsoft Internet Explorer.

With regard to Cookies installed by third parties, you can manage their preferences and withdrawal of your consent by clicking the related opt-out link (if provided), by using the means provided in the third party’s privacy policy, or by contacting the third party.

Limitations of liability

The Owner neither guarantees, nor is liable for damages or harm of any nature that may result from the following circumstances:

  1. Lack of operation of the Website or its incorrect performance;
  2. Lack of usefulness, suitability or validity of the services and content provided on the Website regarding the results and expectations of the User;
  3. Existence of viruses or programmes on the User’s computer.

The Owner shall not be liable, in any circumstance, including negligence, for loss of business, access, benefits, data, for indirect, secondary, special or consequential damages resulting from the access or use of services of the Website, or that are otherwise within its scope.
Since the installation of third party Cookies and other tracking systems through the services used within this Website cannot be technically controlled by the Owner, the Owner cannot be held responsible for the installation and use of such Cookies.
Therefore, any specific references to Cookies and tracking systems installed by third parties are to be considered indicative. In order to obtain complete information, you are kindly requested to consult both the cookies and privacy policies for the respective third party services listed in this document

Updates to the Cookies Policy

After your initial visit to the Website we may change the Cookies we use. This Cookies Policy will always allow you to know who is placing Cookies, for what purpose and give you the means to disable them so please regularly consult our Website in order to be always aware of the rules applicable to the use of Cookies.

Owner

The Website is owned by Overstory B.V., with registered office at Weesperstraat 61-105, 1018VN, Amsterdam, The Netherlands.

For any questions regarding this Cookies Policy, please contact us at info@overstory.ai

Given the objective complexity surrounding the identification of technologies based on Cookies, Users are encouraged to contact the Owner should they wish to receive any further information on the use of Cookies by this Website.