Garmin G3X Touch Pilot's Manual page 217

RUNWAYS
WARNING: Do not use Synthetic Vision runway depictions as the sole means
for determining the proximity of the aircraft to the runway or for maintaining
the proper approach path angle during landing.
NOTE: Not all airports have runways with endpoint data in the database,
therefore, these runways are not displayed.
Runway data provides improved awareness of runway location with respect to the
surrounding terrain. All runway thresholds are depicted at their respective elevations
as defined in the database. In some situations, where threshold elevations differ
significantly, crossing runways may appear to be layered. As runways are displayed,
those within 45 degrees of the aircraft heading are outlined in white. Other runways
(those NOT aligned with the aircraft heading) are outlined in gray When an approach
for a specific runway is active, that runway appears brighter and is outlined with a
white box, regardless of the runway orientation as related to aircraft heading. As
the aircraft gets closer to the runway, more detail such as runway numbers and
centerlines are displayed.
Other
Runway on
Airport
Runway
Selected for
Approach
190-01754-00 Rev. E
Airport Runways
Garmin G3X Touch Pilot's Guide
Additional Features
199