CHAPTER ONE: BENEFITS OF GEOGRAPHIC INFORMATION SYSTEMS
An understanding of the management potential of geographic information systems in law
enforcement begins with awareness of what it can do. Twenty-one different functions of
geographic information systems (GIS) are now being implemented by selected law enforcement
jurisdictions across the country. While most jurisdictions implement only some of the possible functions
of GIS, all jurisdictions surveyed reported significant benefits from implementation of crime mapping.
None of the jurisdictions surveyed reported abandonment or even down-scaling of their experiments with
GIS. On the contrary, most reported plans to expand the number of functions implemented by their
agencies.
The policy implication of this research finding is that the North Carolina Governor's Crime
Commission and other leadership organizations within the North Carolina law enforcement community
should recognize the growing importance of GIS in crime analysis and must work to sensitize
jurisdictions in North Carolina not only to the overall importance of GIS, but also to the opportunities for
its employment beyond such initial functions as pin mapping of crime events. GIS can become a primary
crime prevention and community wellness tool which
can actually be used to help build neighborhood
strength. Furthermore, a GIS-based analytical function
has the potential to allow law enforcement to play an
expanded role in municipal leadership.
Functions of GIS Beneficial to Law Enforcement
Jurisdictions
Pin mapping of crime locations
Pin-mapping is often the initial GIS function
undertaken by law enforcement departments. Crime
locations can be represented as pinpoints on a map. A prominent example of this elementary form of
crime mapping, and the subject of a site visit, was New York City Police Department's CompStat Unit.
Located in the NYPD Command and Control Center, prominent among CompStat capabilities is
computerized pin mapping which displays crime, arrest, and quality of life data in comparative charts,
graphs, tables and other visual formats. Through the use of GIS software and other computer technology,
the CompStat database can generate precinct maps depicting virtually any combination of crime and/or
arrest locations, crime "hot spots," and other relevant information, all of which can be projected instantly
onto the Center's large video projection screens. These visual presentations are a useful and highly
effective adjunct to the CompStat Report since it permits precinct commanders and members of the
commissioner's staff to immediately identify, discuss, and explore trends and patterns as well as
solutions for crime and quality of life problems. (See
http://www.ci.nyc.ny.us/html/nypd/html/chfdept/process.html).
Mapping hot spots
Hot-spot mapping is the spatial representation of areas with high concentrations of crime. This GIS
technique uses contour mapping or spatial clustering methods. Captain Bazemor of the Cary, NC, Police
Department explained the benefits of hot spot mapping in crime prevention:
"If you can use crime mapping to show what areas are being targeted and what areas
actually don't have any problem, then you can assign your resources in those problem areas,
to actually focus on time of day, day of the week and so on. I think that if you saturate an
area with law enforcement, then you are eventually going to prevent something from
happening."
More complex forms of hot spot mapping use statistical techniques like standard deviational
ellipses and k-means clustering to give a statistical
basis to the drawing of hot spot areas on maps.
STAC, from the Illinois Criminal Justice
Information Authority, used by Baltimore County
and other jurisdictions, is a program for this
purpose, as is CrimeStat, from the NIJ Crime
Mapping Research Center (see Appendix B).
Mapping crime density
Mapping crime density values, through shaded
contour maps, involves interpolating crime levels
by using spatial analysis to estimate crime levels
between points of observed crime. A dot density
map shows location and through clustering of dots
can show density, but it has the problem of overlaying dots at the same location, obscuring the true
density. Density surface mapping is a type of contour mapping , with shaded contours linking points of
approximately equal density. Using a color gradient to display increasing density (ex., darker reds), it is
easier to see the true density of any area. The rationale for density mapping was articulated in our Austin,
TX, interview:
"One of the limitations on pin-mapping is that, say you have an apartment complex that
results in a lot of calls and if that address is 1212 Main Street, well, you'll get one dot on the
map, but if you use spatial analysis you'll see that you may have a higher density of crime, so
that density mapping is really good for quickly getting information out to people like patrol
officers and detectives."
Creating briefing maps
The creation of briefing maps for beat-level patrol
officers is the primary method of disseminating
information to the front line of law enforcement. The
strategic view of the analyst and managers must be
translated to the tactical level if GIS and crime analysis
is going to support the officer in the field. Sergeant
Harold Medlock of the Charlotte- Mecklenburg Police
Department made the value of briefing information clear
when he stated:
"GIS maps give us information on what we think we know, but what it tells us a lot of times
is what's going on when we're not working. The thing that officers have to remember is that
they may know what's going on in that response area or in that neighborhood. They're not
working 16 hours a day and two days off a week and they may be on vacation. So to get a
more global picture of what's going on in a neighborhood or geographic area, the maps often
can tell us that our assumptions aren't necessarily what we thought they were."
Likewise, Wilson, NC, Patrol Officer Mark McKenzie described the use of briefing maps in his city:
"We use maps in roll call, when we come in ... Our maps are of the whole city, which has four
districts, and the maps are divided and color-coded for district, and if something specific is going
on, different icons for different crimes, we can look on the map and see what's going on in the
north district, central, south, and whatnot ... Also, since we work four days on and four days off,
we lose a little bit while we're off, and when we come on, we can look and actually see what's
happened in the past week that we've been off, and that helps us to know where we might need
to concentrate our patrol a little bit more, if we're having a problem area."
Mapping for decision-making
Beat, sector, district, and city-wide level maps may be
used routinely for strategic decision-making meetings
in law enforcement. As an illustration, the Durham,
NC monthly crime abatement meeting was attended by
this project's Research Director. In this meeting Chief
Teresa C. Chambers met with all four of her district
commanders to discuss crime abatement. The
centerpieces for the meeting were crime maps provided
by the Crime Analysis Unit, interactively displayed
using a LCD projector. Chief Chambers consistently
focused on two types of analysis as she discussed
crime in Durham districts and the department's strategy
for reducing it: (1) pattern analysis to understand
where crime was located and where was it going
spatially and (2) temporal location analysis of the
crimes as tool for guiding the deployment of officers
at times when crime is most likely to happen. Likewise, from the Wilson, NC, Police Department came this
response on how that jurisdiction routinely uses mapping for decision-making:
"We use maps every week. We have a commanders' meeting where based on the information
from the crime analysis and the mapping, we discuss issues about where break-ins are increasing
in a certain area, or the motor vehicle theft increases, so we use maps daily and weekly. I guess
what the mapping does is, we anticipate the changes going on in a certain area, based on calls
for service, and the unit's home address, what area's given out, what officers are responding all
the time. With the mapping, it's specific about how many we have, what area are they in, and
are they more frequent than they were last month or the year before, compared to time, month
of the year."
The Durham and Wilson examples reflect on small scale the much larger-scale use of mapping as a decision-making aid in New York City's CompStat process, or imitators like Baltimore's CitiStat.
Mapping for pattern detection
Pattern detection maps detect specific, repeating patterns of particular types of crime for purposes of
allocating patrol resources. Criminals exhibit repeating sets of patterns or "MO's" (modus operandi) that can
be as distinctive as a signature. Identifying a criminal's MO and matching it to a pattern of crime often leads
to a successful arrest. In Cary, NC, the police department successfully used pattern detection to apprehend
a suspect for vehicular break-ins and then used the map generated by GIS to prod the suspect into identifying
the location of other cars he broke into:
"I did a map for an investigation that mapped out all the car break-ins. They had developed a
suspect from another agency, charged the suspect on some of the car break-ins and larcenies
from motor vehicles, and knew that he had done more. He said to the investigator, 'I know I've
done more than this but I can't tell you where they are.' So I made a map of all the car break-ins,
and he was able to point out on that map, yeah, I did this one, this one, this one, this one, this
one, which resulted in a lot more clearances for our department."
Integrating interagency data
As crime mapping matures in an agency, data from other agencies may be integrated into the crime mapping
process (e.g., property ownership from tax databases, demographic information from the Census, street light
information from public works, alcohol sales information from the zoning department, etc.). This study's
respondent from the County of Los Angeles noted, for instance:
"From the workstation that I'm sitting on, I can, if I want, know where the street lights are,
where the fire hydrants are, where the sex offenders are, where the parolees live, what the
hydrology is, if I want to know, ad nauseam. If I wanted to tap into an ortho-photo library [a
library of aerial photographs on which map boundaries may be overlaid], I have it on my
workstation." (1)
Some
North
Carolina
agencies
are also
adept at
integrating
data from
other
agencies. Crime Analyst Belinda Pridgen relates how the
Durham Crime Analysis Unit integrated various data sets to
form a picture of how alcohol sales related to various
crimes.
"Sure, we wanted to look at areas where alcohol and beer was being sold in neighborhoods, and
we wanted to look at our demographic information such as income, race, employment levels, and
so forth. And so we took information from a state county planning department, the county tax
department along with other information and we mapped that."
Mapping time-series
Time-series maps can be used to detect seasonality or other time-dependent trends. A series of chronological
overlays can be compared and contrasted, or even animated, to show, for example, how patterns in crime are
or are not related to sequences of vacation days in the public school calendar. The Baltimore County Police
Department routinely uses time series analysis to assess crimes such as juvenile motor vehicle thefts, no force
residential burglaries, and robberies. Using GIS as a tool for preliminary analysis, Chief Statistician Phillip
Canter and his team have isolated both seasonal patterns and target communities of the previously mentioned
types of crime. Analysts were able to determine that juvenile motor vehicle theft, which previously peaked
in the summer, is now shifting to the fall season. This knowledge allowed the Police Department to more
efficiently allocate their resources. Mr. Canter's analysis also indicated that robberies in general tend to
increase in cooler months rather than the more intuitive perception that it increases in the warmer months.
Similarly, by using GIS in conjunction with statistical regression, Baltimore County was able to initiate an
effective crime prevention program for "no force" residential burglaries. The Police Department used an
autodialing system to provide public service messages to the projected target communities, warning about
possible burglaries.
Proximity mapping
Proximity mapping is the creation of spatial buffer zones around an area of interest such as a school, the
address of an offender or even a crime incident. Often a particular type of arrest or crime within a certain
distance from a school may carry a heavier penalty or warrant closer attention. Another use of offender
proximity mapping once used in Cambridge, MA is buffering the address of sex offenders
"In 1996, when we started ... we had somebody working on the sex offender laws in
Massachusetts ... we had a sex offender registry database and we would map radiuses around
their places, so that people could find out if sex offenders lived within a certain radius of their
homes, but that law has been suspended now, in Massachusetts, so it's not extensively
implemented anymore."
Buffering can also be used in a different way, showing the areas of likely criminal opportunity for purposes
of filtering suspects, as the Baltimore Country Police Department does:
"We look at the relationship between where an offense occurs and where the offender's last
known place of residence was, and then we construct a function that describes how far they
would travel to commit a crime. We use that as a guideline to extract out suspects. So we know,
for instance, for firearm robberies, there's so many percent of all offenders that live within about
six and a half miles of an offense location, so if you take a composite buffer that's six and a half
miles from an offense location, there's a good chance that the offender lives within that area."
Mapping spatial displacements
Mapping spatial displacement is tracking the movement of crime patterns over time. For instance, parole
release data may show spatial movement of concentrations of parolees by residence over time. Since in many
cases offenders seem to have a limited range and prefer to commit crimes close to their residence, one may
wish to track crime patterns over time to see if the two displacements correlate, suggesting a recidivism
problem among parolees.
Spatial tracking
Spatially tracking serial offenders is a function implemented, for instance, by the Wilson, NC, Police
Department as early as 1994. Crime mapping staff there noted:
"When there were several rapes in one neighborhood, and then we used GIS, they tracked that
pattern, and then they saw this pattern move to another part of town, so they then looked to see
that too, which led to arrests."
As a second example, Cary, NC, Police Department successfully combined several other functions with
the spatial tracking to locate a suspect responsible for a rash of car break-ins, as noted:
"We also had a case of car break-ins ... They had a suspect, and they said, 'Well, we've got a
clump of car break-ins in one area, and we've got a clump of break-ins in another area.' We were
able to overlay suspects' information, suspects in car break-ins, on that map, and found that there
was a suspect that lived in an area where a bunch of car break-ins were occurring, and then the
other area where a bunch of car break-ins were occurring, the was where suspect's girlfriend
lived, so they were able to clear those cases as well."
Resource allocation
Resource allocation involves using spatial analysis to create service zones or patrol areas, or using network
analysis to establish emergency response routes or patrol routes. Our interviewees in Charlotte-Mecklenburg
were able to manage overall police workload more efficiently with this function of GIS technology:
"Through the redistricting effort that we did, GIS enabled us to use a number of different data
sources that we hadn't used in the past and did it in a more effective manner, and we were also
more efficient because we cut down on the number of hours that it actually took ... we basically
sat in a room with all the district captains and in one day, accomplished what took two people
six to nine months to accomplish in the past."
Our Cary, NC respondent also reported similar success in using GIS to redistrict police beats. When asked
to relate a success story she considered a "best practice" for others Jennifer Morgan said:
"Our beat redistricting maps ... made redistricting our beats a simple process rather than
something that was extremely complicated."
Additionally, the Charlotte-Mecklenburg department, which other analysts in the state acknowledge as the
state's leading innovator in methods and technology, uses GIS as a tool for resource acquisition: Officials
there noted:
"We only had six officers in Mecklenburg County dedicated to ABC enforcement, but by using
GIS we showed them what the problem was and they (ABC Enforcement) allowed twelve of our
officers, which did not cost the state any
additional revenue or anything like that, to
have those powers. We pretty much tripled
our coverage in a short time."
Real-time response mapping
Real-time response mapping is implemented in
Surry County, NC, for instance, where an E911
system and CAD software allow the dispatcher
to capture the address of the caller and generate
a digital street map showing the quickest route
to an incident (Newcombe, 1995). There is a
perceived need for real-time mapping in North
Carolina as elsewhere. (2) From the Winston-Salem, NC, interview, in response to the
question about how crime mapping services
could be improved in the future:
"More timely, current, accurate information ... to have things set up on in-car computers ... I can
see when an officer goes out and investigates a break-in, he says, 'I wonder how many
break-ins we've had in this area before?' ...and say 'Here's five other break-ins just like that,
and then how many of them broke in the front window, and keep narrowing it down."
Mapping in community policing
In a community policing context, maps are an effective way of sharing information with Neighborhood
Watch and other community groups to encourage community-police cooperation in law enforcement. From
the Winston-Salem, NC, interview:
" We're incorporating the community ... ministers, community
representatives, activists in the
community, probation and parole. We've
identified areas that are hot spots
involved in that. This is really the first
thing that we've really done with GIS
mapping, and based on that we're getting
the community involved, to go out ...
we're going out in the community, with
community members. We're getting the
community involved in this and they see
the maps, they see the power of this and
why it's important. There's no end to
what we can do with that, and it fits right
in with problem-solving policing."
Similar use of crime mapping for Neighborhood Watch and other community outreach efforts was reported
in Wilson, NC. In Durham, Captain Beverly Council noted how crime mapping can correct community
misperceptions:
"You have a perception that you've got a drug problem, you have a perception (that) has to do
with crime, but the map and the information
we've got shows otherwise, and they can use it
in that manner to get them started to help lay
some groundwork for community policing."
Mapping recovery operations
Recovery operations mapping is the overlaying
the locations of theft and recovery of stolen
vehicles or other property. This is done, for
instance, in Winston-Salem, NC, where a
patrolman described how recovery operations
mapping works:
"[Using crime mapping] every two weeks, officers know right now
certain areas that suspects will frequently dump stolen vehicles, and that's what we're concentrating
on now ... and we're also coming out with showing recovery locations along with theft locations to
show that, if the pattern changes ... say five vehicles
were stolen from Hanes Mall, and all of them have
been recovered on the east side, by New
Walkertown Road ... officers may head straight to
that area ... if he's not there, then, great, but if he is,
then we're there also."
Spatial situational analysis
Situational analysis is the analysis of types of crime by types
of setting. For example, crime mapping may focus on
analysis of crime in abandoned buildings; analysis of crime
in establishments serving liquor; analysis of crime in high
schools; overlaying setting maps to understand possible
interaction of settings. 
Spatial situational analysis includes target profiling, as in comparing convenience
store locations with actual convenience store robberies. For instance, the Lenexa, KS, Police Department
applied spatial situational analysis to construction sites:
"We had a big problem with construction site theft, and so we plotted the locations of the
sites that had already been hit, then went into our building permit files, in the Planning
Department, and overlaid all the permits that had been issued. We did some surveillance on
the sites that hadn't been hit yet, and were able to capture the folks as a result of that."
Similarly, the city of Wilson, NC, used situational analysis to successfully stake out targets and apprehend
criminals when it had a problem with crime in abandoned buildings, and again when it had a problem with
crime in churches.
Spatial historical analysis
GIS may involve historical analysis of non-crime events in relation to crime events (eg., producing spatial
profiles of crime related to sporting events, for purposes of allocating patrol resources for future scheduled
sports events). While this form of crime mapping analysis is still rare, in Greensboro this method is planned
for fall, 2000, in relation to that city's major stadium.
Multivariate pattern analysis
Multivariate pattern analysis is the comparison of multiple variables and their spatial patterns based on
incident reporting with patterns determined by some other database, such as based on dispatch data, warrant
data, or crime victimization survey data. For instance, the Winston-Salem, NC, respondent noted:
"We look at where we've got our intensive probationers and we've got access to the jail lists,
and we even look at who's been arrested for house break-ins and watch these, and who's in
custody and who's not, and where they live, and where they're found burgling at. Based on
that, we developed a trend just recently where my break-ins went up 75 percent when they
see particular people got out of custody, and when they went back
in, they dropped about 75 percent and the MOs are the same every
time ... We found out that our case management system,
unfortunately, looks at each case, when the case is referred, on a
case by case basis ... [but with GIS] we were able to develop a
pattern, a trend, and suspects, that we were able to focus on those
key individuals, and make arrests, and both of them are in custody
now with charges of several break-ins. We wouldn't be able to that
without mapping."
Tactical crime analysis using suspect databases
Tactical crime analysis uses suspect databases to understand the
spatial relation of distribution of suspects for a crime category in
relation to the distribution of actual crimes in that category. Tactical analysis includes linkage analysis listing
known suspects within a given distance from selected incidents. C. K. Lamm of the Wilson, NC, Police
Department reported:
" I've set up several maps, on a monthly basis, where we'll check our field interviews that we do,
and put them on top of the maps where our crimes are occurring and see what the relationship is between
whoever we were doing our field interviews with and where we're having crime."
Orthophotographic mapping
Orthophotography is integrating aerial photographs as detail backdrops for map projections. The city of
Wilson, NC, for instance, used orthophotographic mapping in its alcohol-related enforcement campaigns
to allow ALE agents to see the area surrounding targets of interest better when looking at maps.
Spatial modeling
Spatially modeling is modeling crime based on the past history, poverty, or other determinants of crime
using a structural equation simulation or other statistical methodology. This advanced technique was rarely
undertaken by any of the cities in the North Carolina or national survey. Mesa, Arizona, however, was an
exception where basic correlation analysis was undertaken: (3)
"Yes, we had a request to look at some socioeconomic grouping in a specific section of the city,
and so we had Census data and some socioeconomic data, and put that together with some crime
density mapping, and were able to show some great tendencies towards hot spots in the lower
socioeconomic areas ... Upper management was looking at developing some community policing
projects in the area and also looking at possible neighborhood grants for developing some
projects to help reduce the crime in those areas."
Chapter summary
In summary, each of the 21 functions of GIS illustrates a significant way in which crime-mapping with GIS
technology benefits law enforcement and plays a significant role in crime abatement. These various functions
embody a range of difficulty of implementation, with very few surveyed jurisdictions having introduced all
of them. The simplest function is pin mapping, which is the first function that most jurisdictions implement.
Pin mapping is the gateway to the other crime mapping functions in part because the ability to implement
good pin maps implies the jurisdiction has successfully addressed its data needs and has reliable base street
maps. As skill and experience increase, crime analysts must go beyond pin mapping to more challenging
functions with greater payoffs. Making communities aware of the range of possible GIS functions in law
enforcement is a helpful step in laying the basis for strategic planning for GIS and was recognized as such
by the respondents in our survey.
Notes:
1.
Interagency data cooperation is also noted by Bryan Hill of the Phoenix, AZ, police department: "Our data and information on crimes and traffic problems are also shared with other city departments for support of numerous other programs and work done within the city. (i.e. traffic crash data supplied to streets and engineering to assist their analysis of roadway design, grid crime counts provided to planning, liquor licensing, and other departments for use in quality of life research and studies in those departments.)."
Note: The March 2000 Juvenile Accountability Incentive Block Grant Bulletin, titled "Establishing and Maintaining Interagency Information Sharing," includes a model interagency information sharing agreement (Publication No. NCJ 178281)from the National Criminal Justice Reference Service, Office of Juvenile Justice and Deliquency Prevention, http://www.ncjrs.org/ncjpubs.htm. Other examples of interagency data sharing agreements: the Baltimore-Washington Regional Crime Analysis System has a memorandum of understanding which includes rules for data sharing and information exchange, contact: Wes Westerfeld (tel. 410-333-2595; wwesterfeld@baltometro.org); the Cincinnati Metropolitan Housing Authority has a Law Enforcement Agreement with the Cincinnati Police Division, contact: Charlie Murray (tel. (513) 977-5347); Orange County, CA Chiefs' and Sheriff's Association data sharing agreement, contact Prof. James W. Meeker of the University of California - Irvine (jwmeeker@uci.edu). Also of interest, the U. K. governmental guide to sharing data between the police and other agencies: http://www.homeoffice.gov.uk/cdact/guidcrp.htm. The Mobile, AL, Police Department has data sharing agreements with the Corps of Engineers, DOT, FEMA, the county school board, EPA, FBI, and others; contact Lt. Eddie Burrow, Police Planning, (334) 208-1914).
2. To take another example, the Delaware State Police, Real Time Crime Reporting (RTCR) Mapping
System, is integrated with police vehicles equipped with mobile data computers, GPS receivers, and
printers.+ (Contact Pam Harrison, pharrison@state.de.us; tel. 302-739-596). Another example of real-time mapping exists in the Baltimore County Police Department:
"Each police car has an AVL, an Automatic Vehicle Locator, that's using a global positioning
system, and that transmits a signal to a CAD computer that has a mapping capability to it, and
they can see where the car is located."
In Boston, police officers reported that their new real-time CAD system
"is a lot better than using a pin map ... We get information right now, not when headquarters gets
around to sending it to us" (Nesbary, 2000: 17).
3.
Another form of spatial modeling was carried out by the Baltimore County Police Department:
"We did [spatial modeling] with domestic violence, and attempted to identify areas where we
thought these types of crimes may be under-reported. We've developed something called Public
Safety Indicators, and by using timely information, primarily obtained through CAD data, we've
been able to identify communities that we feel are going through some sort of transition, and it's
sort of like a community distress model, but it works very, very well, and it allows us to be
somewhat pro-active in that sense. You know, where a lot of it's based on social disorder theory,
for example, but we look for certain symptoms that a community might be exhibiting, that could
suggest that it's going through some sort of change, one way or the other. It might be a positive
change, too."