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COVID-19 Human Activity Monitoring (HAM) with Satellite Synthetic Aperture Radar (SAR) Observations is a NASA-funded project to monitor human activity level change around the world due to COVID-19 lockdown and re-opening. Scientists at NASA’s Jet Propulsion Laboratory and the Earth Observatory of Singapore are processing a large volume of satellite radar data to produce maps of human activity level for about 100 major cities in the world to address the following questions:

  1. How have reductions in human activity varied across different cities?
  2. Do reductions in activities correspond to the different levels of success of different cities in controlling outbreaks of the virus? 

Parking lots are usually exposed to satellites and can represent human activity level. In order to validate and quantitatively analyze their results, the scientists are currently trying to classify a number of ground targets in Los Angeles County into several business types; however, the relevant parking lot locations, shapes, and extents vary from one business to another.

They requested GISCorps volunteers to draw a polygon of the parking lot of each given business. 20 volunteers were deployed to the project and the following report was submitted from JPL’s project lead, Sang-Ho Yun. When JPL scientists decided to expand the project two months later, 66 additional volunteer roles were filled for a second round of digitizing.

Project Report

The COVID-19 pandemic is currently bringing unprecedented impact to every aspect of human life, from an individual level to local community, city, county, state, country, and global scales. In order to combat the spread of the virus, communities and governments have imposed restrictions on human activity. The severity of these restrictions has varied from city to city, from voluntary social distancing all the way to full lockdown situations where entire populations are banned from leaving their homes. The changes in the level of human activity resulting from these measures can be detected and monitored using spaceborne SAR observations, by mapping changes in the interferometric coherence, which indicates the similarity of the contents of any pixel in a SAR image from one epoch to another. Reductions in human activity can result in increases in SAR coherence, since there are fewer surface changes during the quiet time.

NASA’s Jet Propulsion Laboratory (JPL) and the Earth Observatory of Singapore (EOS) have produced several SAR-based products that can help to quantify levels of human activity. The Slowdown Proxy Maps (SPMs) provide city-wide maps of activity reduction in and around the month of March 2020. These will help to highlight areas of dramatic activity reduction due to COVID-19 responses. Following the mandatory or voluntary lockdown, the human activity gradually resumed over spring to early summer of 2020. The degree and location of the recovery signals (Recovery Proxy Map, RPM) are mapped using similar technique.

The GISCorps volunteers helped the project by creating polygons of parking lots that are visible from space and indicative of human activity level changes. The project is using the volunteers’ products to track the temporal variation of such human activity over the polygons. The project is introduced on NASA’s website. The relevant products are being posted at NASA’s dashboard with as well as a tri-agency (NASA, ESA, JAXA) dashboard. The study is currently ongoing, however GISCorps volunteers’ involvement has been concluded.

This preliminary map shows the slowdown of activity at Disneyland in California. Areas in blue indicate a reduction in vehicle concentration or movement as a result of COVID-19 pandemic response efforts. (Credits: NASA/JPL-Caltech/EOS at Nanyang Technological University)


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