Tuesday, July 17, 2007

GPS requires extra manpower, budgets to implement

Reacting to this Grits post on the limits of GPS tracking, Bexar County probation officer Bryan Shreve describes his personal experience with the limits of GPS systems at the Texas Council on Probation blog:
The antiquated Radio Frequency (RF) system currently used by caseload officers in Bexar County is less costly and looks good on paper. However, the RF does not provide real time GPS tracking and alerts. GPS monitoring along with many other duties (field visits and other contacts) for the officer is a good tool to monitor the whereabouts of the offenders. That being said, GPS requires a great deal of manpower and specific monitoring with a dedicated staff to be on-call to respond to the alerts. It also requires offenders to plan and submit schedules to the officers for approval. Sounds good, but this cost money and effects budgets.
Shreve concludes that "GPS is an important tool, but the officer actually performing random field visits and conducting searches of offenders homes and vehicles for illegal items and possible victims should be the most important duties of our profession."


Anonymous said...

GPS usage also requires some reality-checking.

Once while using a Garmin Etrex handheld while walking in a residential neighborhood in Los Angeles County, I got an average speed of 127 km/hr.

There was no sign of loss of signal, so clearly there was pronounced multipathing ('ghosting'), which introduces correlated noise into the signal processing. While the timing may be tightly fixed, anomalous positional errors obviate the utility of GPS as a precise tracking system.

Someone with an ankle-tracker, under house arrest, could be asleep in his own bed, yet the gadget could report him as being kilometers away (and moving at high speed).

I suspect the authorities will routinely cover up tracking errors, which means that a gadget can bear false witness without being subject to perjury laws.

Anonymous said...

Experience and training on how to use the GPS system along with recognition of those "ghost" points, is extremely important. Those who rely on one alarm or a bad set of points to judge an entire system really doesn't have the proper training. This is a technical field that requires formal training. When I first supervised a GPS caseload, I had the same questions and concerns. After I gained the experience and learned the map system, it became a valuable tool. When thete are GPS alarms and errors, it is monitored and tracked to assure the accuracy in reporting. Those sitting on the sidelines may not truly understand the man hours spent to set up and "calibrate" the equipment. It's a job. The alternative is not knowing where the offender goes when he or she leaves your office. It is not a perfect system and like cellular phones can't be tracked 100% of the time everyhwere on the planet. A person would need to use some walking around sense to interpret real alarms with loss of signal alarms. This is why it is important to not rely on one specific alarm or signal. Using multiple points, times, speed, etc., will give anyone reading the tracking a clear picture as to where the offender travels.