Tiles
A Tile is the sky area covered by the detector array at one step of a Mosaic Pattern traversal. The location is determined by the base pointing and orient for the Observation, combined with the offset of the corresponding Mosaic Pattern.
In APT for Roman, Tile visuals are represented by a simplified version of the Wide Field Instrument (WFI) footprint. The Tile visual is a oblong rectangle that covers a sky area of size 0.7 degrees by 0.4 degrees. The Figure Showing a Tile Relative to the WFI Footprint provides a visual aid for understanding how APT for Roman shows the WFI footprint to design Mosaic Patterns.
Figure Showing a Tile Relative to the WFI Footprint
The Tiles used to plan Mosaic Patterns are simplified into a rectangular region that is approximately 0.7 degrees by 0.4 degrees instead of using the true footprint of the Wide Field Instrument (WFI) that has an arching pattern of detectors. The actual WFI footprints fit together to fill the area in the Mosaic Pattern and, in practice, most Tiles will not be single exposures, but rather use Dither Patterns to fill detector gaps.