I plotted a geofence with a 100 meters radius, I didn't get a notification that the geofence had been hit until I was 200 meters past the radius of the geofence. So I want to know how many meters beyond the geofence radius is still considered within geofence region?
Have a look here. It is really worth reading:
Depending on what localization solutions the devices can access, it may be that precision is about 100-200m which is what you observe.
In addition there is a delay to trigger notification. Did you try moving 50m away from the geofence and wait there for some time (typically 20 seconds) to see if event is triggered ?
Read also h ttps://developer.apple.com/library/content/documentation/UserExperience/Conceptual/LocationAwarenessPG/Introduction/Introduction.html
Region events may not happen immediately after a region boundary is crossed. To prevent spurious notifications, iOS doesn’t deliver region notifications until certain threshold conditions are met. Specifically, the user’s location must cross the region boundary, move away from the boundary by a minimum distance, and remain at that minimum distance for at least 20 seconds before the notifications are reported.
The specific threshold distances are determined by the hardware and the location technologies that are currently available. For example, if Wi-Fi is disabled, region monitoring is significantly less accurate. However, for testing purposes, you can assume that the minimum distance is approximately 200 meters.
As Claude dutifully quoted, the process waits to send an alert to be sure you're not going in and out of the specified region. I can go quite a ways in 20 seconds, so where you're claiming it was based on 200m, you might want to rethink that distance.
In your case, the true radius is 100m.