- SPECIAL REPORTS
- THE MAGAZINE
Many POB readers are land surveyors and civil engineers who have a unique opportunity to offer GIS services to local governments and utilities. To set the stage for a discussion of those services in an upcoming article, let's first look at how a GIS might be used in a typical municipal government. Let's also discuss the ways things were done before the GIS was installed so that we can understand some of the benefits GIS produced.
Consider a typical town of approximately 20 square miles in area with a population of roughly 30,000. Let's look at the operations of the municipal government, assuming it installed a GIS several years ago. We'll visit the town hall and take a tour of several departments using GIS:
- Tax Assessment
- School Board
- Public Works
- Public Safety
- Tax Assessment
Tax AssessmentThe first stop on our tour is the tax assessor's office located on the ground floor. This department is responsible for assessment and collection of taxes on the town's 11,000 tax parcels. In the past, the tax assessor maintained two principal types of tax records: a set of tax maps and a set of real estate files. The tax maps were drawn in ink on mylar at a scale of 1" = 200'. Thirty map sheets were required to cover the town at this scale. These maps showed the city boundary, the rights of way, street names, the boundary lines of all property parcels, street addresses, lot numbers, block numbers and section numbers for all parcels. Parcel dimensions had been penciled in on a few of the larger and more prominent parcels.
These tax maps were first compiled about 20 years earlier by the state Department of Taxation from property records. The drafting section of the town's engineering department kept the tax maps up to date as new subdivisions were recorded, roads were built or town limits changed. After the revisions were made, the originals were copied and a new set of paper prints was distributed around town hall. Revisions were made on an irregular basis, but usually about every three months.
When the town bought a mainframe computer in the early 1980s, then a client-server system in the 1990s, the tax assessment system and records migrated to these new systems. The tax assessment office has a full-time data entry clerk who updates these real estate files daily. These updates are made necessary by new subdivision recordings, property transactions and the annual reassessment. The updates are made at a computer terminal in the tax assessment department linked to the minicomputer.
When the town installed a GIS, the tax maps were among the first to be digitized. The town hired a service bureau to take its 30 tax maps and digitize them in a format compatible with the GIS that was being purchased. As each of the tax parcels was digitized, it was also tagged with the parcel identification number.
After the tax maps were loaded into the GIS, the software was able to link the graphic files describing parcel boundaries with the real estate files containing tax parcel data, as illustrated in Figure 1. The parcel identification number made this linkage possible, even though these two sets of files are maintained on separate computers.
Very few people now require paper copies of tax maps. Instead, when someone calls or drops in for tax map information, they can call it up on a GIS terminal at the public information desk. Town employees can access the GIS data from the computers on their desks. Tax map and assessment data are also available over the Internet. The tax assessment office maintains a web page and provides tax maps and assessment data through a simple query screen. The GIS gives them a continuous map of the entire town.
The tax assessment department still updates the real estate files that reside on the town's first computer, just as it did before. But the annual reassessment of all properties is handled much differently. In the past, the tax assessor would sit with a tax map and a computer listing of the real estate files to conduct his reassessment. It was a very tedious process for him or her to correlate tax parcel data shown on the maps with tax records in the computer printouts. Today, that same person sits at a GIS terminal and obtains that same information in a fraction of the time. The tax assessor can ask the GIS to search the real estate files for properties with certain characteristics, and the GIS will not only find them in the real estate files, but identify them on the tax maps as well. For instance, a tax assessor may want to know all the properties in a neighborhood that have sold in the past year and their selling prices. The GIS can quickly find this information.
PlanningNow let's go to the Planning Department. In the past, the town planner used the engineering department's draftsmen to update the town land-use plan and zoning maps. The originals were drafted in ink on mylar at a scale of 1" = 1,000'. These maps showed the town boundary, streets, street names and major landmarks. The land-use map also showed planned land uses and the zoning map showed the current zoning of all parcels in the town.
One of the problems with these two maps was that, at this scale, it was not possible to show parcel numbers or street addresses. Therefore, the planning department also kept a set of paper tax maps and added the zoning boundaries to it using a felt-tip pen. The zoning boundaries were updated from time to time as the town council approved zoning changes. Unfortunately, there was the problem of conflicting information between the annotated tax maps and the "official" town zoning map.
Since the town's GIS was installed, the planning staff has added the zoning boundaries and land-use plan boundaries to the GIS database. This has given them several important benefits. When searching for routine information about a parcel, a planning department employee simply types in the parcel number or street address instead of trying to locate the parcel on the official plan and zoning maps or searching through the annotated tax maps. Moreover, special planning studies can now be done much faster than before.
For instance, the town manager frequently asks the town planner to research questions such as; Where are all the parcels that are larger than 5 acres and zoned for industrial use? Or a member of the town council may ask how much undeveloped land is planned for residential development. He or she now uses the GIS terminal in the planning department to answer these questions. (Figure 2.)
RegistrarThe last stop we'll make on the first floor of town hall is the Registrar's office. The registrar uses the GIS in two ways. When new citizens come in to register to vote, he or she can quickly determine in what voting district they reside. The registrar simply types in their address at the GIS terminal and the system searches for the address in its database and then compares this location with the overlay of voting precincts. Before the GIS was implemented, it was difficult to locate the citizen's house. This was usually because the citizen was moving into a new subdivision, and the new streets had not yet been added to the paper copy of the town street map. Today, these street-map changes are immediately available as soon as the engineering department updates the GIS database.
The registrar also uses the GIS to analyze voting districts. State law requires that the voting districts be re-examined after every census. The GIS can compare precinct boundaries with the Census Bureau population data and count the number of voters in each district. The registrar can try new precinct boundaries and immediately receive a recount of the population in the newly defined precincts. He or she can play this "what if" game to arrive at an even distribution of voters with a fraction of the effort that was required in the past.
School BoardNow let's walk upstairs to the office of the town's school board. The school board's facility engineer uses his or her GIS terminal to retrieve engineering and architectural drawings of the schools. All of the paper drawings were scanned into a digital format about 15 years ago. Since then, all new drawings have been submitted in CAD format, as required by town code. The engineer can display a map of the town, click on the location of a school and see a list of all the drawing sets available for that building. He or she then selects the drawing set and the drawing of interest, and it is immediately displayed on the computer screen. This system has replaced the large sets of flat files and hanging files that used to be in the engineer's office.
The school facility engineer also works with the town's public transportation manager to plan school bus routes (see Figure 3.) Because the GIS includes an overlay of U.S. Census Bureau demographic data, they have access to the most recent census data on school-age children. This data helps them to plan school bus routes that evenly distribute the student passengers on each bus. In the past, bus routing was done largely by intuition, and trial and error.
Engineering and Public WorksThe largest department of the second floor of town hall is public works. The director of public works is responsible for the town survey crew, the drafting operation, building inspection and permitting, maintenance and operation of the town's water and sewer systems, public transportation, solid waste removal, public buildings and general engineering design. He or she is also responsible for the maintenance of all the graphic data in the GIS database.
The town survey crew uses an automated survey data collector for its field survey operations. This device allows the crew to record measured angles and distances automatically. In the past, these data were recorded by hand in field survey notebooks. Instead, the data collector records the point being occupied, the backsight station, the foresight station, the angle turned, the distance to the station, as well as a code describing each of these points. The survey crew uses a keypad on the side of the instrument to record station identification numbers and other descriptive codes.
When the survey is complete, the crew brings the data collector into the office, connects it to a data port in their PC and uploads the survey notes from the data collector to a CAD system. The CAD program reads the data and calculates x, y coordinate values for all points surveyed, as well as their elevation. The program also plots the data in the CAD file, using symbology appropriate to the type of point surveyed. Thus, if a highway was surveyed, the curb lines, manholes, sidewalks, poles and so forth are automatically plotted by the system using the proper drawing symbols. This automated process eliminates the time-consuming and tedious process of "breaking down" field notes, calculating locations and plotting a drawing by hand. When the file has been checked and the drawing finished, this CAD data is used to update the mapping data in the GIS.
The survey crew also uses a GPS survey system. This system was first used in the 1990s to establish a network of ground control points around the town, all referenced to the state's mapping coordinate system. Ever since, it has been relatively easy to tie all new survey work into the state mapping system. Because the GIS uses the same coordinate system, these surveys can be registered to the data in the GIS.
Whenever digging permits are issued to utility contractors, the county "Miss Utility" service is called in. This service uses electromagnetic sensors to locate any underground utilities in the excavation area. These locations are then spray painted on the ground. The town survey crew uses this opportunity to survey the exact location of the utility line. Using its GPS system and employing a procedure similar to that used with the automated survey data collector, this survey data is automatically recorded and plotted in the CAD system. This data is then used to update the location of utility lines shown in the GIS. About half of the town's utility line locations have been verified and refined in this manner. As a result, both the town and the local engineers have come to rely on the utility locations shown in the town's GIS when designing new utility systems or improvements in the public right of way.
Public Utilities Department
The public utilities department uses the GIS to manage the town's water and sewer systems. In the days before the GIS, the department used two sets of maps: one showed the location of water mains and fire hydrants; the other showed the locations of sanitary sewer mains and manholes.
These two utility-system maps were drawn by hand at a scale of 1" = 1,000'. They showed pipe sizes and slopes where appropriate, but they did not have more detailed information such as pipe inverts, date of installation, pipe materials, manhole rim elevations, water pressures, etc. This detailed information had to be found by searching through construction drawings.
Unfortunately, there was often confusion, even conflicts, in these drawings because not all as-built information had been collected or kept up-to-date. So, it was often necessary to verify utility data in the field. This required the survey crew to spend half a day or more gathering or verifying utility data.
Today, utility department personnel can use their GIS terminal to research utility data. For information about a particular manhole, they might call up the sanitary-sewer system map for the town and window the area in which the manhole is located. They then identify the manhole in question by pointing to it using the workstation's mouse. The system responds with a report on the manhole's attribute data, including invert elevations, rim elevation, date of installation, etc.
Moreover, they can ask the GIS to search for information using questions such as, Where are all the storm sewer lines larger than 24" in diameter? Or, where are all the water valves installed before 1950? The system will search its attribute files to locate these facility items and then display them on the workstation screen.
The public utilities department found that one of the great unexpected benefits of implementing the GIS was that it required a total clean up of all utility data. To load the GIS database, all unknown information had to be researched and all conflicts in the existing data had to be resolved. This was a major effort, but today the operation runs much more smoothly because the data is readily at hand and reliable.
In the future, the public utilities department plans to add programs that link the engineering and topographic data in the GIS with standard engineering analysis programs. These include hydrology programs for performing rainfall runoff computations and hydraulics programs for analyzing the flow in pipe systems and performing flood-plain computations.
The engineering department is responsible for utility and roadway design. This department was successful in convincing the town to get relatively detailed topographic mapping at 1" = 100' with a 2' contour interval (see Figure 4). Although this cost more than the less-detailed mapping required by other departments, it has been very beneficial. The detailed topographic data provides a much better base for registering the utility and tax map data that was added to the GIS. Also, less field survey work is required for engineering designs.
The engineering department was also successful in convincing the town to require that all plan submissions to the town, such as for new subdivisions or for new utility systems, be made in a digital format compatible with the town's GIS. This has made it much easier to incorporate new data into the database and keep it up-to-date.
The public works department first established a GIS department when the system was installed. The GIS manager is responsible for overall GIS promotion, maintenance and operations. The GIS system manager is responsible for supporting the GIS database. This includes daily file backup and archiving, contact with hardware and software vendors and establishing user access privileges.
A GIS cartographer is responsible for maintaining the graphic files in the GIS database. This job involves updates to the tax parcel boundaries, topographic and planimetric data, utility data, and planning and land-use data. The town recognizes that as it grows and the GIS database grows, some or all of these database maintenance functions may have to be decentralized to the user departments.
The GIS system manager also provides user training for new employees, advanced training for existing employees and technical support to the users. This technical support includes troubleshooting, answering routine questions, referring problems to the vendor and minor programming tasks. Programming is done chiefly to customize the basic capabilities of the GIS for the GIS users. This programming is done principally using the GIS macro programming language.
Public SafetyOur final stop on this tour takes us to the police department's public safety center, which is across the street from town hall. The town's chief dispatcher is responsible for the operation of the public safety center. In the past, his or her dispatchers used a variety of reference materials to direct responses to police, fire and rescue incidents. These included a collection of United States Geological Survey (USGS) maps, a town street map and a collection of hand-drawn subdivision map sketches. The reference materials also included a directory of street address ranges and an index card file. This card file contained important phone numbers, property owners' names and addresses, and an inventory of hazardous materials and buildings with invalid occupants. New dispatchers required several months on the job to master this eclectic set of references.
Shortly before the GIS was installed, the town installed an E911-telephone capability. When the GIS was installed, it was linked to the E911 system. Today, when a call is received through the system, it transmits the caller's address to the GIS (Figure 5.) The GIS then automatically locates the address and displays the tax map for the surrounding area on a console in front of the dispatcher. A target in the middle of the display pinpoints the caller's location. Thus, while the dispatcher is responding to the incident and directing response units, he is also presented with a map of the surrounding area. Information regarding the address, such as the presence of hazardous materials, is provided from the E911 database.
The GIS also assists the dispatcher in routing the responding unit. The dispatcher points to the location of the available unit or units, and the GIS calculates and displays the route that each unit should take to report to the scene. Either the shortest distance traveled, the shortest time required to make the trip, or the fewest number of left-hand turns can determine these routes. The GIS will even display and printout directions for the responding unit to follow to the incident.