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New method to implement Geofencing Disclosure Number: IPCOM000246445D
Original Publication Date: 2016-Jun-07
Included in the Prior Art Database: 2016-Jun-07
Document File: 3 page(s) / 320K

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Du, Q.W.: INVENTOR [+2]


1). To devide the erea of goe fence into rectangle blocks 2). To decide whether one block belonging to the geo fence or not 3). To use a bitmask/bitmap to stand for geo fence definition 4). To link multipe pieces of such geo fence definition together to generate a complex geo fence definition 5). To broadcas multile versions of one geo fence with different accuracy under different system busy state.

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New method to implement Geofencing

Quawen Du, Huakun Yang, Phoenix Wang

Motorola Solutions



This disclosure introduces a new method to define a geofence. The method divides a geofence area into multiple blocks, uses array of bitmask to indicate whether one block is in the range of one geofence. With this new approach, there is smaller footprint and less MIPS requirement to calculate whether one position is within a geofence border or not. The method is beneficial to embedded devices with limited resource to save the geofence area definition or calculate whether a location is in range of a geofence. The method is also suitable to transmit the geofence definition across narrowband network with higher speed because of its smaller footprint.   


The existing definition of one geofence is typically a circle or polygon. The accuracy of a circle geofence and the size of footprint to hold the irregular polygon are known challenges for embedded devices. The situation becomes worse when delivering a polygon geofence through a narrowband network such as LMR.

In either circle geofence or polygon geofence, it is complex for devices to determine whether one location is within one geofence or not. The devices execute complex arithmetic calculation which requires much MIPS, which is always a problem for embedded devices.

In short, we need a new method for an improved precision of a geofence, smaller footprint and easier for devices to determine whether one location is within one geofence or not.


In the solution, we define a fence as the collections of multiple smaller blocks. To use a traditional geofence via polygon as example below:

In the new solution, we divide the geofence into rectangular blocks as below:

Based on the layout above, we define the geofence as:

·         Anchor location: the top-left point to coordinate the blocks

·         Size of one block: the width & height of each block

·         Number of blocks: the numbers of blocks on X-axis and Y-axis

·         Bitmask array: to indicate whether one block is within the geofence or not

According to the shape of one user defined geofence and the precision requirement of the geofence, the user is able to define all these parameters above. Given one area, the size of each block impacts the precision of the geofence definition, number of blocks and bitmask array size so impact the footprint to represent one geofence.


With the solution, the footprint is calculated as below:

For anchor location, assume 3 bytes are enough to stand for a location X or Y respectively, then total 6 bytes are good enough to stand for one anchor location. When deploying the solution, the anchor location is possible to be relative to a fixed and known point, 4 bytes are enough.

For block size definition, according to different deployment strategy, the footprint requirement is different. In some embodiments, if the subscriber and infrastructure share the same and known block size definition, the block size can be zero....