a virtual limit (= one that does not exist physically) that can be placed around a particular area using satellite technology, in order to record or limit the movements of a person, vehicle, etc.

When an individual crosses a geofence, an alert is sent to their device and the operator of the geofence is notified. 当有人越过地理围栏时，警报会发送到他们的设备上，并同时通知地理围栏的运营商。

to use satellite technology to place a virtual limit (= one that does not exist physically) around a particular area in order to record or limit the movements of a person, vehicle, etc.

To geofence an area, you must first establish a virtual boundary around a specified location using GPS-enabled software. 要对一个区域进行地理围栏，你必须首先使用支持GPS的软件在指定地点周围建立一个虚拟边界。