The Ins and Outs of CAD Systems


Law enforcement managers take note—your database can play a more important role than you realize in achieving safe and effective inter-agency sharing. The high-profile Pima, Arizona shooting of Congresswoman Gabrielle Giffords and 18 citizens that occurred on Jan. 8, 2011 offers a great example.

At 10:11 a.m. Southern Arizona’s Pima County Sheriff’s Department started receiving what would become several hundred calls for help, where dispatchers entered the calls into computer-aided dispatch (CAD) software, including assailant details, and quickly assigned nearby units to respond. Deputies used laptops to see the address and location of the shooting on a map, the status of all responding units, and a list of real-time call comments describing both the attack and the assailant. The first deputy arrived at the scene at 10:15 a.m., four minutes after the initial call was received.

As the severity of the incident became apparent, dispatchers called for backup from neighboring agencies, including the Oro Valley Police Department and Marana Police Department, eventually ten total agencies. These departments had CAD system sharing arrangements with Pima County, giving officers access to real-time updates on the address, location, responding units and call comments.

By 10:16 a.m., Jared Loughner had been arrested, and medical personnel were treating the injured. Deputies identified the shooter, recovered his driver license, entered his name into the shared records system and discovered a record from the Pima County Community College Police Department from September 2010, when he was suspended for being disruptive in class and posting inflammatory videos on the Internet. From that record, deputies could see Loughner’s address, previous criminal incidents, known associates, and vehicles registered in his name.

Pima County’s Public Information Officer Dawn Barkman characterized the role of the database in the CAD system: “This incident would have been a complete chaotic mess if communications had to deal with it in the old CAD system that did not directly interface with a relational database, or even scarier, [deal with it] on paper.”

Benefits of CAD, and what to look for

Advanced CAD systems deliver information that ensures greater safety and improved situational awareness for officers responding to emergency calls.

Real-time versus cached

In 2000, the U.S. 911 system handled an average of 500,000 calls daily (about 183 million annually), according to the Center for Problem-Oriented Policing, and how calls are handled varies throughout North America. For example, when 911 calls or texts come into an emergency call center, a dispatcher enters the information into the CAD system, then determines which field unit should respond. Systems set up to cache data may cause a delay of critical seconds between entering the call and assigning the field unit. However, when a CAD system can deliver data in real-time, officers may see the call data as it is entered, even before the dispatcher selects the available unit to respond. In the field you may realize that you are closest and respond, shaving off vital seconds.

The database also determines whether the CAD and the mobile systems access the same database or data sets, or requires an interim step to move data between the two systems, slowing communications.

Inter-system and inter-agency sharing

CAD systems extend beyond computing devices and software, and may link to other systems such as alarm inputs, mobile data systems, time synchronization sources, records management systems, other agencies; and local, county, state and federal criminal justice databases.

Since 9/11, the focus has been on improving information-sharing between agencies and jurisdictions. Federal Guidelines for Governance Agreements in Public Safety Information Sharing Projects state, “Advancements in public safety CAD, records management systems , and other associated systems have made it efficient and safe for multiple agencies to share the administration and support of these systems. Meanwhile, the development and wide adoption of the National Information Exchange Model (NIEM) standard have made it technically easier to share data.”

Database admin

Beyond how they control speed and access to data, databases influence overall CAD system costs. A PricewaterhouseCoopers study reported 70 percent of database costs occur after implementation. Databases fully integrated within the application eliminate ongoing licensing, support, and upgrade costs, and can eliminate the need to hire an experienced database administrator.

What’s new in CAD data?

Data access and retrieval

Originally developed by IBM for mainframe computers, the Indexed Sequential Access Method (ISAM) offers an efficient central data access approach. ISAM has evolved to allow developers to use an application programming interface (API) to search indexes and locate records in data files.

Applied to CAD systems, combining ISAM and master tables allows individual records to be retrieved without searching the entire data set. For example a “Master Names Table” allows a single name to be quickly retrieved, regardless of where the name is used or referenced in the overall system.

Without ISAM or master tables, name information for a single individual may be located in multiple places, like incident records, vehicle records, warrant or arrest records, etc., making the search time-consuming at best. At worst, search results may miss vital information needed for an arrest. During a traffic stop you might not see an outstanding arrest warrant or other relevant criminal activity.

Speed of search

A central data repository contributes to faster search speeds. ISAM’s precise control of index structures returns fast search results because ISAM allows CAD systems to control which elements are searched, according to how the data has been indexed.

New advancements have shattered information access barriers across multiple data formats (relational and non-relational), by layering ISAM and SQL into a single database. The database engine maps the non-relational data into a relational (or tabular) model on-the-fly, providing SQL access to this data. Public safety agencies particularly favor CAD systems with this dual capability when their personnel are proficient using SQL to run reports, but want faster performance possible with ISAM.

Furthermore, ISAM was designed to embed the database directly into applications or data files, a unique feature that stands apart from SQL-only databases like Oracle and Microsoft SQL Server. ISAM maintains data index integrity by collectively describing hierarchical data and index file relationships, which permit a single call to the data engine to then update a record and all of its key values. Then when new information is entered and associated with a name, the database updates all records associated with that name, regardless of where it is used or referenced.

Advanced CAD systems help officers responding to emergencies and crime scenes by increasing safety and situational awareness. They contribute to the nationwide effort to increase inter-agency sharing. But not all CAD systems are equal. Ask yourself: Does the CAD system allow for creation of precise indexes for quicker searching? Does it deliver information as it is happening, or does it cache and refresh it only periodically? Will there be added costs for maintaining the database?

To best understand these systems, you must consider the database. Like the engine of a car, it powers CAD systems and plays a key role in determining its levels of speed, performance and cost.

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