TrimTrac ProE Locator, Technical Manual

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TrimTrac ProE Locator Technical Manual v2.0e 21
Geofence Shape and Size
Once the centerpoint of the geofence has been determined, you must then define
the overall dimensions of the geofence area. In the case of rectangular geofences,
you will need to define the due East-West and North-South lengths. Alternately,
you would define the diameter of the circular geofence area.
Since the geofences used by TrimTrac are orthographic projections, latitude and
longitude distortions increase as distance from the center point increases. As
such, the maximum length of any given geofence dimension is limited to 1000
kilometers. For rectangular geofences, this means no side can be more than 1000
kilometers. The diameter of a circular geofence is similarly limited to 1000
kilometers.
Geofence Type
Finally, you will need to define the type of geofences that will be used. All
geofences in the TrimTrac ProE must be of the same type, of which there are
three choices: Boundary Crossing, Inclusive and Exclusive. In the case of
Boundary Crossing, the TrimTrac ProE will send a geofence-triggered report each
time the TrimTrac ProE detects it has crossed the boundary of an active geofence.
This report will be transmitted, along with a message indicating which geofence
had its boundary crossed, regardless of how the Report Delay Flag is set.
In the case of an inclusive geofence area used in conjunction with the Report
Delay Flag, the device will not normally transmit position or status messages
whenever it is located inside the defined geofence area. As soon as a position is
computed that is outside the geofence area, the device will commence
transmitting position and status reports as if the Report Delay Flag is set
“0=Transmit (‘Tx’) All Messages”. The device will continue transmitting in this
mode until the device re-enters the inclusive geofence area.
Conversely, the device will begin transmitting position and status reports
whenever the device is inside an exclusive geofence area.
The relevant parameters, settings, messages and commands used to define and
activate geofences are set forth in Table 8 on the following page and in Table 97
on page 196.