How electronic fences work
Will the positioning accuracy affect the accuracy of the fence alarm? How to improve the alarm accuracy?
As shown in the figure, the administrator specifies a series of coordinate data on the server in advance to delineate the scope of the electronic fence.
The location device periodically reports its location data, including coordinate data and location time, to the server. The server compares the two adjacent location data with the range of the electronic fence, based on the comparison results to infer whether the device has entered or left the fence:
If the previous piece of location data is within the fence and the next piece of location data is outside the fence, a “Leave the fence alarm” is triggered.
If the previous piece of location data is outside the fence and the next piece of location data is inside the fence, an “Enter the fence alarm” is triggered.
If both pieces of data are within the fence, or both are outside the fence, no alarm will be triggered.
Taking Figure 1 as an example, the two adjacent bits reported by the device are position points A and A1. A is outside the range of the fence, and the following position point A1 is within the range of the fence, then the “Enter the fence alarm” is triggered.
The two adjacent bits reported by the device are position point B and B1, B is within the range of the fence, followed by position point B1 is outside the range of the fence, then the “leave the fence alarm” is triggered.
how is the false alarm/missing alarm/delay alarm generated?
If the device uploals the location data at a long interval, or fails to locate the device when it enters a building, culvert, valley, or tall building, the two adjacent location data may be far apart. The device may have actually crossed the fence, but the two adjacent pieces of location data received by the server fall outside the fence, so it will not trigger an alarm, resulting in a missed report.
The coordinates C and C1, shown in Figure 1, are outside the fence, so no fence alarms will be triggered. In fact, the device crossed the fence between the two data, but the server could not know the true motion path of the device only according to C and C1, so the alarm was missed.
Is the electronic fence a function of the device side or a function of the server side?
Electronic fence is a server-side software function, and its data processing is on the server side, and it does not need to be calculated on the device side. The location data processed by the electronic fence comes from the device, and as long as the device regularly reports its location data to the server, the server can achieve the electronic fence function
Will the positioning accuracy affect the accuracy of the fence alarm? How to improve the alarm accuracy?
It will be. Each positioning method is affected by many different factors, and the positioning accuracy obtained is different. Because the location accuracy is not high enough, the location data reported by the device may be far away from the actual location, which may cause the server to make false alarms, false alarms, or delayed alarms. In addition, if the device uploads the location data at large intervals (for example, every 30 minutes), it will also reduce the accuracy of the electronic fence alarm. Considering that increasing the positioning frequency usually leads to large power consumption, it is necessary to comprehensively consider the actual use scenario of the wearer and the battery capacity of the device to set the appropriate positioning frequency.
In addition, when the device is in a small street between buildings, culverts, valleys, mines, or tall buildings, the GPS signal will be blocked and the positioning will fail. If the positioning accuracy obtained through Wifi positioning is insufficient here, you can consider using Bluetooth beacons to assist positioning.
Thinkrace has developed Bluetooth beacon-based positioning and electronic fencing capabilities, please contact us for more information.
Introduce Our Products
ThinkRace, a leading manufacturer, specializes in comprehensive electronic monitoring solutions for the justice industry. We offer a range of products, including electronic restraints and smartwatches, designed to cater to the needs of offenders, law enforcement officers, and command personnel. Our hardware and software solutions are tailored to meet the critical business requirements of various stakeholders within the sector. Choose from our diverse product lineup to address your specific monitoring and security needs.
