Table 1.
Metrics used in this study, along with their definitions and resolutions provided by Facebook
| Metric | Units | Definition | Spatial resolution provided by Facebook | Temporal resolution provided by Facebook |
|---|---|---|---|---|
| Population density | Number of Facebook users | Average number of Facebook users within a Bing tile during an 8 h period | Bing tile level 13 and 16 | 8 h |
| Population flows | Number of Facebook users | Number of Facebook users that shared the same modal tile across two adjacent 8 h time periods | Bing tile level 12 | 8 h |
| Distance travelled* | Kilometres | Total distance between tile centroids ‘travelled’ by Facebook users across two adjacent 8 h time periods | Bing tile level 12 | 8 h |
| Co-location | – | Probability of two Facebook users from varying Pitney-Bowes administrative regions are present within the same level 16 Bing tile during a random 5-min bin | Pitney-Bowes administrative regions | Weekly |
| International movement | Number of Facebook users | Number of Facebook users moving between two countries within a single day | Country | Daily |
*Distance travelled is not a metric directly calculated by Facebook