In order to identify the home and work locations of a device, a reference grid is created across the U.S. and Canada.
A grid (100m) is chosen as a home grid if it is one of the top 5 locations for the month where the device spends nights. In the U.S., this is restricted to parcels that are zoned for residential use. In Canada, the homes are where the device spends the nights with no other restrictions. We then weight each of the 5 possible home locations according to the number of nights the device spends there throughout the month.
A grid is chosen as a work grid if it is one of the top 5 locations for the month where the device spends the weekdays.
Night-time hours are defined as 7pm to 8am (+/- 1 or 2 hours depending on the exact time zone and data month) 5pm to 6am. Work hours are defined between the hours of 11am to 4pm on weekdays (M-F)(+/- 1 or 2 hours depending on the exact time zone and data month). This means that if someone is working the night shift at a factory in a grid that overlaps a block that is zoned for residential use, the factory grid may appear as the device's home and the grid where the night-shift worker sleeps during the day may appear as the device's work location.