GPS

How It Works

You've probably heard about GPS before, but you may not know how it actually works. Here's a brief explanation.

GPS stands for Global Positioning System. GPS was developed by the U.S. Department of Defense as a precise navigation system for military applications, but has since been opened up to the public.

Twenty-four GPS satellites orbit the earth, constantly emitting radio signals. The satellites are positioned in space so that at least four are visible from any point on earth, at any time. These satellites are the foundation of GPS. Because these GPS satellites constantly "rain" signals down on the earth, anyone with a "bucket" or GPS receiver can "catch" them. Three people could have GPS tracking devices or three billion. It makes no difference.

A GPS receiver needs to "know" where the satellites actually are in order to calculate the receiver's location. This isn't particularly difficult because the satellites travel in very high and predictable orbits. The GPS receiver simply stores information regarding the satellites' position at any given time. Things like the pull of the moon and the sun do change the satellites' orbit very slightly but the Department of Defense constantly monitors their exact positions and transmits any adjustments to all GPS receivers as part of the satellites' signals.

When a GPS receiver locates and "catches" GPS signals, it measures how far away it is from each of at least four separate satellites. By calculating several locations over time, the GPS receiver can also compute speed and direction of travel.

iSECUREtrac takes this technology several steps further by combining communication networks, both landline and wireless, with web-based management software. The company also incorporates several sub-systems to detect, record and report non-compliance and any attempts at monitoring circumvention.

iSECUREtrac GPS systems record location points several times a minute. These devices contact the iSECUREtrac monitoring center at regular intervals and "tell" iSECUREtrac's computers where the monitored individual is, where he's been since the last contact and whether or not he is in compliance with pre-established supervision parameters. The systems then place the updated information on the iSECUREtrac electronic management reporting website so that corrections personnel can check the individual's location and status. Supervising officers can also create geo-fences or boundary zones where the individual is prohibited from going (e.g., elementary schools, spouse's residence, known gang hangouts, etc.) or where his presence is required (e.g., his residence, place of employment, counseling offices, etc.). These boundary zones are more commonly referred to as inclusion or exclusion zones. If the offender violates these zones, the supervising officer can elect to be notified.

Both passive and active GPS can be set to warn the offender that they are getting home late or are too close to a place that is off-limits. With onboard intelligence, alerts to offenders take place immediately – even when the tracking unit cannot access cellular service to communicate with the host.

Active and Passive Systems

At the most basic level, there are two types of GPS systems: active and passive. An active GPS system uses a cellular communications network to report locations and violation status. Passive GPS provides the same information but on a delayed basis. Passive GPS usually downloads information a couple of times during a 24-hour period. An Active GPS system, on the other hand, provides location information much more frequently throughout the day and reports violations as they happen, assuming there is cell coverage.

Hybrid GPS Systems

There are GPS systems that can operate in both passive GPS mode (delayed notification) and active GPS mode (real-time violation notification). These are hybrid systems. Typically, they provide real-time notification of certain types of violations (e.g., exclusion zone violations) with delayed reporting of locations and all other violations a couple of times a day. These systems send information to the agency over a time period that is usually much longer than with active GPS, but more frequently than is typical with passive GPS. Hybrid systems typically use cellular technology to transmit the location and compliance status data.

There's a big difference, however, between hybrid systems that have onboard processing or intelligence and those that don't. Those that do will start reporting more frequently as soon as the tracking unit determines a zone violation has occurred. Those that don't may not start reporting more frequently for hours – depending on when the next time the unit was scheduled for regular reporting.

You could argue that a "Hybrid" system with onboard intelligence is more active than an "Active" system without it.

Assisted GPS

There is also something called "assisted GPS" or A-GPS. There are two types: network assisted and network based. Usually, A-GPS requires an active connection to a cellular communications network and an assistance server. With network assisted, the assistance server supplies orbital data to the GPS tracking unit enabling it to locate and lock on to GPS satellites much faster than would otherwise be possible. Once locked onto GPS satellites, most GPS systems calculate locations autonomously and without further assistance. However, there are some systems that continue to rely upon other technologies (e.g., cell phone or TV broadcast towers) to compute locations. It's iSECUREtrac's position that those devices provide less reliable and consistent data. In the absence of cell or broadcast coverage, for example, location data become less accurate.

With network-based, the location is actually computed by one of the ground based GPS servers. The tracking unit passes the data it receives from the satellites to the server over the cellular network. Then the server sends the location back to the tracking unit where it is stored until the next time it sends data to the host computer. These systems cannot compute their GPS location when they are outside of a cellular coverage area.

Two Piece GPS Systems from iSECUREtrac

iSECUREtrac two piece GPS systems are comprised of two main components: an ankle bracelet or cuff and a Personal Tracking Unit (PTU). The ankle cuff is electronically tethered to the PTU via a radio frequency (RF) signal. If the PTU does not receive an RF signal transmission from the cuff, the PTU records a violation. This violation may indicate that there was an attempt to abscond or circumvent electronic monitoring. Numerous strategies are used by agencies to investigate these violations – including violation resolution by iSECUREtrac's Monitoring Center staff.

iSECUREtrac two piece GPS systems consistently take, compute and store multiple tracking points every minute, not just when the individual is in a violation status. These stored points are complete with time/date stamps and velocity information. This is extraordinarily useful when the monitored individual is in an automobile and can change location, speed and direction in less than 60 seconds. Systems from other companies may take a single point as infrequently as once every 10 minutes.

The more often the system takes points, the fewer and the smaller the gaps in tracking data. This is particularly true when the offender is in an area with spotty cellular coverage and the system relies upon Assisted GPS. However, it's also true when the offender is traveling through areas where buildings, tunnels, bridges and other obstructions along the route are likely to block GPS satellite signals. The savvy offender may be able to take advantage of systems that track infrequently or those more likely to miss tracks – creating a tracking history that provides far less certainty about offender behavior than systems that record tracks frequently and are less subject to "missing" tracks.

In addition, storing multiple points every minute provides necessary detail on the location and movement of high-risk individuals, including the direction and speed of travel. With more points, it's easier to more accurately discern patterns of travel and travel routes. If there is a deviation from a firmly established pattern, it may warrant further investigation by the supervising officer.

For more information or to request an on-site demo of iSECUREtrac systems, services and software, email or call toll-free at 866.537.0022.

Ultra-Active GPS: The System 5000

iSECUREtrac offers agencies two, two-piece active GPS options: regular active and active GPS with landline capability (ultra-active). Ultra-active GPS can be defined as a GPS monitoring system that has both onboard intelligence AND the ability to use both land-line and cellular communications networks in communicating with a monitoring center.

Personal tracking units (PTUs) with onboard intelligence are able to autonomously compute a GPS location without calling into a server to determine the compliance of the program participant with inclusion or exclusion zone rules. If the individual is in violation, an immediate alert is sent to the computer server and the agency, Command Center and/or the iSECUREtrac Monitoring Center. The speed with which these alerts are generated provides officers with minutes or perhaps hours of more response time which is a unique feature of systems with onboard intelligence.

On board intelligence combined with the ability to record multiple points per minute even when no violations have been detected gives iSECUREtrac's active GPS systems the fastest response time in the industry. As soon as the individual is in violation, the GPS system communicates with the monitoring center over a cellular network which processes the information. According to pre-established protocols, the monitoring center alerts the supervising agency/agent, makes the information available online, and archives the information for later reference. The supervising officer can use any Internet-ready device (e.g., laptop) to see where the offender has been and when he was there. iSECUREtrac electronic management software provides agencies with updated information in easy-to-understand, easy-to –adjust formats including maps with aerial overlays, violation reports, tamper and equipment status and much more. When unable to access the Internet, a call to the monitoring center can provide the necessary information.

Advantages of the System 5000 ultra-active GPS include:

  • Dependable, consistent tracking performance when in or out of cellular coverage.
  • More tracks, less gaps.
  • The fastest "Immediate Alerts" in the industry.
  • Immediate offender warnings and acknowledgements with or without cellular coverage.
  • In the absence of cell coverage, reporting of participant status and tracking data through a traditional land-line or when the program participant is back within cell coverage.

The agency uses a single electronic management software program for GPS, House Arrest/Curfew Management and Alcohol Monitoring. This software can be accessed from virtually any PC connected to the Internet. No additional software is needed. While logged on, an officer can access and change participant information and can create edit, and delete schedules/curfews, and establish inclusion and exclusion zones.

For more information or to request an on-site demo of iSECUREtrac systems, services and software, email or call toll-free 866.537.0022.

Active GPS

iSECUREtrac Active GPS is a two piece system that includes onboard intelligence and utilizes a cellular communication network in communicating with the iSECUREtrac Host Computing Center. In areas with adequate cell coverage, iSECUREtrac delivers the fastest violation alerts on the market. If cell coverage is inadequate, the PTU processes and stores locations and violations. It continues attempts to report data to the Host Computer until cell coverage is adequate and the data download is complete. Meanwhile, delayed reporting is not apparent to the offender as he continues to receive real-time zone violation warnings. In addition, iSECUREtrac active GPS can be switched to cellular House Arrest remotely and with the virtual flip of a switch.

The advantages of iSECUREtrac active GPS includes:

  • Dependable, consistent tracking performance when in or out of cellular coverage.
  • More tracks, less gaps.
  • The fastest "Immediate Alerts" in the industry.
  • Immediate offender warnings and acknowledgement with or without cell coverage.

The agency uses a single electronic supervision case management application for GPS, House Arrest/Curfew Management and Alcohol Monitoring. This software can be accessed from virtually any PC connected to the Internet. No additional software is needed. While logged on, an officer can access and change participant information and can create edit, and delete schedules/curfews, and establish inclusion and exclusion zones. When a PC isn't available, the monitoring service center provides customer support 24 hours a day, 7 days a week.

For more information or to request an on-site demo of iSECUREtrac systems, services and software, email or call toll-free 866.537.0022.

Passive GPS

iSECUREtrac Passive GPS utilizes the same advanced technology as iSECUREtrac's Active GPS Systems. For example, the Personal Tracking Unit (PTU) utilizes onboard intelligence to autonomously compute GPS locations and compare those locations to compliance parameters stored in the unit, to assess the individual's compliance status. The individual can then be notified in real time that he/she is non-compliant. Rather than report violations to a Command Center in real time, however, iSECUREtrac Passive GPS provides delayed reporting a couple times during a 24-hour period while the PTU is docked within a charging base that's connected to landline communications.

Agencies may prefer delayed reporting when:

  • Zone rules aren't relevant to the case plan or there is no expectation for immediate response to zone violations.
  • GPS is being used as a crime deterrent and crime solving tool.
  • The least restrictive form of supervision is being applied and the purpose is to provide an audit trail of location behavior with few or no schedule/locations restrictions (except those necessary to keep the equipment charged and operating.
  • Staffing resources are not available for off-hour response to violations and there are inadequate funds for outsourcing violation investigation to, for example, the iSECUREtrac Monitoring Center.
  • There is little cellular coverage and it is critical that all tracking points are available for review at the end of the day

The same detailed reporting available through iSECUREtrac's active systems is available with iSECUREtrac's Passive GPS. For example, iSECUREtrac Passive GPS system consistently takes, computes and stores multiple tracking points every minute and not just when the individual is in a violation status.

Most agencies use a combination of systems in their community supervision programs. To determine which iSECUREtrac systems (Ultra-Active GPS, Active GPS, Passive GPS and Alcohol Monitoing) are most appropriate for your agency, it's recommended that you and your iSECUREtrac representative discuss supervision goals, the risk to public safety from individuals participating in the program, and other program parameters.

The advantages of iSECUREtrac Passive GPS include:

  • Autonomous GPS for dependable, consistent tracking performance.
  • More tracks, less gaps.
  • Offenders receive immediate warnings for behavior that can be addressed the next day.
  • Tracking points and compliance status are available for officer review as soon as the client comes home and docks the Personal Tracking Unit in its charging base.
  • Avoidance of officer stress and burnout when sufficient staff or budget levels aren't available to support a 24 hour alert response.

The agency uses a single electronic supervision case management application for GPS, House Arrest/Curfew Management and Alcohol Monitoring. This software can be accessed from virtually any PC connected to the Internet. No additional software is needed. While logged on, an officer can access and change participant information and can create edit, and delete schedules/curfews, and establish inclusion and exclusion zones.

For more information or to request an on-site demo of iSECUREtrac systems, services and software, email or call toll-free 866.537.0022.