There are several ways to implement a multi- purpose GIS system, depending on the goals and objectives of the people who will use the information. However, many government jurisdictions have implemented GIS without understanding the fundamentals necessary to properly implement the system to serve current as well as future needs. This paper will review the process and procedures that the Polk County Property Appraiser set up for a successful multi- user and multi-purpose GIS, using survey accurate GPS points and tieing parcel maps to land corners using coordinate geometry. It will go over the essentials of how the project was started, the development of interlocal agreements, the construction of the pilot project, the "digital assembly line", and establishing committees to set policy, direction, and address technical issues.
Polk County, Florida is located between Orlando
and Tampa, and is one of the largest counties,
geographically. It covers almost 2,000 square
miles with 280,000 real estate parcels and a
population of 437,204. There are 155,969 owner
and renter occupied units. Polk has been the
largest citrus and phosphate producing county in
the United States, and one of the largest cattle
producing counties in the state. It is a major
warehousing distribution hub and serves as the
corporate headquarters for Publix Supermarkets,
Discount Auto Parts, and Babcock Furniture Stores,
as well as the regional corporate headquarters for
State Farm Insurance and Breed Technologies. The
County has 17 municipalities, with the cities of
Lakeland (pop. 73,794), and Winter Haven (pop.
25,126) being the largest. The winter months
brings an influx of winter residents from the
northern states and Canada. Recently, parts of
the county have become bedroom communities for
both Tampa and Orlando for residents who want to
enjoy a more relaxed way of living with less
congestion.
In Florida, nearly all the Offices of the Property
Appraiser(previously referred to as the Tax
Assessor)are elected offices with the duty to
locate and appraise all property in the county,
including tangible personal property. This
responsibility is not limited to the
unincorporated areas but also includes the
municipalities.
In an effort to more effectively manage
information, avoid redundancy, and to reduce the
expense for the constituents and customers of Polk
County, the Polk County Property Appraiser had the
vision to start the development of a county-wide
Parcel Geographic Information System that would
integrate maps, text, and photographic data.
Until January 1, 1993, the mapping process was a
manual one and involved maintenance of 8,500 maps
at different scales. There was no automated
method of performing spatial analysis, map
production, or map maintenance.
The State of Florida, and its counties, were
originally surveyed based on the rectangular
survey system, with the exception of Spanish land
grants. Township and Range lines were established
in the 1800's at six mile intervals, thereby
creating a grid of 36 square mile areas. Each
township and range area was further broken down
into its surveyed 36 sections ("square" miles),
which are again broken down to quarter and quarter
quarter sections. This forms the basis of the
land ownership system which the legal descriptions
are derived from. In our manual parcel mapping
system each section or "square" mile consists of a
cover section sheet at 1" to 400', followed by any
number of additional maps representing various
areas within the section, such as subdivisions or
enlargements, at 1" to 50', 1" to 100', or 1" to
200'. Any section could comprise from one to
possibly fifty individual map sheets. To convert
these maps to create a geodetically accurate,
seamless, contiguous digital map, in real world
state plane coordinates, would be a formidable
task.
The Property Appraiser, in October 1992, hired a
Director of GIS to start the conversion process.
The first task was to find out who in the county
or cities were already using or wanting to acquire
a GIS system. The County had started a digital
mapping project in the Planning department, but
the data and accuracy were not acceptable for a
multi-purpose/multi-user GIS system. The City of
Lakeland had started an AM/FM (Automated
Mapping/Facilities Management) system using
Intergraph and Microstation software for their
Electric Utility Service Department. The service
area is five times larger than the corporate city
boundary.
In 1991 Lakeland had contracted and obtained 240
square miles of rectified photo enlargements and
digital planimetric data. The planimetric data
consisted of street centerline, edge of pavement,
hydrography, railroads, and street names. This
data was based on sub-centimeter accurate survey
points that were targeted in the aerial
photography, thereby guaranteeing the overall
digital map feature accuracy to within a foot of
real world location. Additionally, the Department
of Environmental Protection had put in a high
precision, sub-centimeter accurate, 6 mile
geodetic grid covering the entire county in 1991.
Both the Lakeland and DEP surveys were Second
Order Class 1 accuracy, exceeding the Federal
Geodetic Control Committee's standard for using
GPS. The DEP survey was done with the written
understanding that the County would further
densify the control network. Over $400,000.00 of
excellent survey, planimetric, and rectified photo
enlargements were readily available to use without
the Property Appraiser having to reinvent the
wheel or duplicate what already existed.
Although Lakeland had an accurate planimetric
base, they needed a complete parcel coverage that
would match their map accuracy requirements. In
January, 1993, Lakeland and the Polk County
Property Appraiser's Office entered into an
interlocal agreement. The City would provide the
planimetric base and two contract employees, along
with some hardware and software, while the
Property Appraiser would develop the parcel GIS
data over a three year period with his GIS staff
(Director, Unix System Administrator, and an
ArcInfo analyst), along with four cartographers.
The Property Appraiser would start the operation
with a combination of 2 SUN workstations and
several PC's tied together over a local area
network.
It should be pointed out that in states, like
Florida, that use the rectangular survey system,
it is not possible to develop a seamless, accurate
parcel base without section geodetic control.
Many local governments have used the process of
board digitizing paper maps or scanning maps and
performing digitizing on computer screens.
However, you have to evaluate the product going
into the conversion process as well as the
conversion process itself. The accuracy of the
geometry and legal descriptions must be referenced
to the geodetic control in order to validate the
positional accuracy in the real world. Good
planimetric and digital ortho-rectified
photography can assist in the placement process
but the geodetic control along with the coordinate
geometry is the most important feature for
geometric accurate placement of the vector data.
Although Lakeland's aerial photography and
planimetric data were tied to high precision
geodetic control points, there were little, if
any, section control points available with state
plane coordinates. Therefore, the initial plan
called for the Property Appraiser to scan each
section of map mylars, make them all the same
scale, use coordinate geometry to develop the
subdivision boundaries and perform a raster rubber
sheet of the scanned maps to the subdivision
geometric boundaries. The staff would also
perform heads-up digitizing of the interior lines,
text, and meets & bounds parcels, and place the
finished digital data on top of the planimetric
data primarily using the edge of pavement layer to
place the subdivision and parcel boundaries.
This appeared to be a good approach, considering
that we did not know or have access to the section
coordinate control points. A pilot project area
was selected and the results were both good and
not so good. The good news was the pilot
demonstrated that we could do the job in a
reasonable amount of time, and that the parcels
had a good relative fit to the Lakeland data.
However, the down side was that without the
section and quarter section coordinates to tie to,
the parcels were as close as two feet to a land
corner or as far away as forty feet where we did
not have a subdivision in a corner location.
Without tieing the legal descriptions to the land
corner geodetic coordinate control we could not
guarantee an exact real world fit in all areas.
The results of the pilot caused us to rethink our
methodology and make some strategic changes to the
program. We met with the County Administration
and the City of Lakeland to set up a coordinated
program to locate and obtain state plane
coordinates for all section and most quarter
section land control corners. Lakeland had
already purchased Trimble GPS survey equipment and
agreed to give the county the use of these
devices, provided that the Lakeland Electric
Utility Service Area was surveyed first. The
County agreed to allow the County GPS surveyor to
head up this program with a survey crew, working
under the leadership of the County Property
Appraiser's GIS Director as the Project Management
Agency. This meeting saved the project an
additional $80,000.00 by using the City's
equipment.
This proved to be the decisive turning point that
would enable the Property Appraiser's GIS system
to turn into a multi-purpose/multi-user GIS
system. Many of the County departments as well as
the cities have a real need for the Property
Appraiser's parcel maps, associated tax roll, and
appraisal data. We demonstrated the difference in
the pilot area between the accuracy of using
coordinate geometry tied to survey control points
as opposed to scanning, rubber sheeting, and
heads-up digitizing. The process of choice was
obvious if we were going to do the project right
the first time for long term benefits by all
participants. All coverages or "layers" would be
accurately placed with the survey control and
coordinate geometry using the planimetric base as
background coverages. Using the edge of pavement
and the hydrography proved to be a excellent way
of facilitating one level of quality control. We
could now deliver an accurate system for everyone
to use and build upon.
The cities of Auburndale (pop. 9,132), Winter
Haven (pop.25,126), and Eagle Lake (pop. 1,923),
signed interlocal agreements with the Property
Appraiser's Office on September 9, 1993, October
27, 1993, and March 9, 1995, respectively. The
Polk County Board of County Commissioners signed
an interlocal agreement on August 30, 1994, to
assist in developing a total system with all
participants. The City of Lakeland is also taking
the lead providing digital street addressing
program, and will share that data with the
Property Appraiser, saving the County an
additional estimated $300,000.00. The formulation
of these interlocal agreements allow each
participant to receive a state of the art GIS base
system for the least amount of cost, with one
project management agency being the hub of the
organizational wheel.
The core project team was subsequently expanded.
The Property Appraiser added an additional
cartographer and the Board of County Commissioners
supplied two regular employees as cartographers
along with one contract person. The cities of
Auburndale and Winter Haven jointly supplied a
contract professional land surveyor to work as a
cartographer. This turned out to be an
outstanding working example of how local
governments can partner with each other, avoiding
redundancy and high costs, for the best return on
their investment.
The Property Appraiser's GIS/CARTOGRAPHY section
was reorganized based on the additional personnel.
We developed an "assembly line" approach for the
digital conversion process, and firmed up a
maintenance team of five cartographers to
concentrate on the tax roll deed changes, with
some overlap responsibilities. The conversion
team consists of the ArcInfo Analyst, a
professional land surveyor/cartographer, two
mappers, and two text/annotation digitizing
personnel. Each stage of digital map conversion
is quality controlled before it moves along the
digital assembly line.
After each section is fully digitized it is
brought into the active ArcInfo system for any
subsequent maintenance changes. The new digital
section is also inserted into a map library for
total seamless contiguous coverage for inquiry and
analysis. At that time all sections and coverages
are available to all local county departments over
a fiber optic computer network. The cities will
receive their updates monthly via tape transfer
until a high speed network is in place.
The initial project consists of building the
following coverages and associated "layers":
Geodetic
GPS points
Meander lines
Section points
Quarter section points
Reference text
Government lot text
Hydrography
Edge of lakes, rivers, streams, and
canals
Water body names
Culverts
Drainage ditches
Parcels
Parcel boundary lines
Parcel number
Parcel dimensions
Lots
Lot lines
Lot number
Lot dimensions
Subdivisions
Subdivision boundary lines
Subdivision name
Subdivision number
Municipal
Municipal boundary lines
Municipal text
Miscellaneous
Right of way centerline line
Street Name
Right of way easement
Right of way text
Right of way dimensions
Electrical easements
Electrical easement text
Railroad lines
Site tract lines
Site tract dimensions
Site tract text
Misc. Text
Misc. Lines
Arrows
Problem
Problem lines, text, etc.
Edge of Pavement
Edge of hard surface
Edge of dirt road
Bridges and overpasses
Roads
State roads
Major collectors
Major collectors unpaved
Minor collectors
Minor collectors unpaved
Local county roads
Local unpaved county roads
Private roads
City streets
Routine only maintenance roads
New roads picked up from the photography
Road Intersection Nodes
Intersection with traffic light
Intersection of road and driveway with
traffic light
Cul de Sac
Double Boulevard
Railroad intersection
Intersection without traffic light
Node for street name change
Each coverage contains data elements to further
define its features, including point, line, and
polygon topology, and associated attribute data.
For instance, the parcel lines are coded so that
the lines can depict whether they are lakefront or
road frontage. Standards have been set for overall
symbology and schema. Each coverage has from one
to sixteen "layers" defining the feature. In
addition digital ortho-rectified photo can be
viewed as a separate or background coverage. The
photography, at one, four, and eight foot pixels,
is placed into an image catalogue for quick
reference. For detail viewing users can call up
the one foot pixel images. For large area
viewing, like a complete city, users can use the
four or eight foot pixel photography. And we are
currently in the process of linking the digital
map to selected tax roll and appraisal
information. This process involves moving the
data to a relational database so the GIS system
can query the data and graphically show the
results in the map, like showing where all
properties with homestead exemption are that have
a mailing address that is different from the
physical street address for follow up action.
The project timetable covers a period of eight
years, start to finish. The county has been
broken down into 4 major areas for completion (see
fig. 1). The areas and timetable were selected
based on population and parcel density, selected
city participation, and the need for digital map
data for emergency management, traffic
engineering, roadway maintenance, utilities, and
natural resources. The completion of each area
allows the delivery of a working GIS system for
comprehensive usage. The completion of each
section into the system allows complete use of
that area regardless of overall area or project
completion. This methodology allows the system to
be used as it is being developed over the project
timetable.
The project requires densifying the high precision
geodetic control network, obtaining digital ortho-
rectified photography and selected planimetric
features for the parcel mapping process. The
reconnaissance and obtaining state plane
coordinates of the land corners is an ongoing in-
house function. These activities are coordinated
by the GIS Director, with overlapping schedules to
balance the project requirements (see fig. 2). A
maintenance program is established to keep all
data up to date.
Perhaps the most technically challenging aspect of
the project is placing the subdivision and parcel
boundaries using state plane geodetic reference
points and plats and legal descriptions. It is
one thing to write a separate legal description,
with bearings, angles, and distances for a
subdivision or parcel without regard as to the
real world fit of that polygon into the larger map
picture and quite another challenge to accurately
place that polygon into the larger map puzzle.
Often there are overlaps and gaps that need to be
reconciled. Decisions need to be made based on
original intent, errors in legal descriptions, and
insufficient or erroneous survey information.
These decisions require good judgement and common
sense together with expertise in mapping real
world parcel data. A consistent set of standards
and procedures must be adhered to in making these
decisions, as well as providing research to
realize justified solutions.
Additionally, the County GPS Surveyor and his crew
must locate the best evidence found in the
vicinity of the section and quarter section
corners. At times they will find several markers
in close proximity to each other. This requires
the Property Appraiser's conversion staff to check
out the points in relation to the legal
descriptions and plats, thereby verifying the
one(s) which provide the best fit for the overall
immediate map area. Additionally, it can be
challenging for the survey crew to obtain
permission to enter properties, let alone finding
the corner evidence. Of course there are times
when no corner evidence is possible (lakes), or
the corner no longer exists. In these cases we
require the survey crew to locate points on the
nearest subdivision(s) for proper section
placement, while referring to adjoining sections
for verification of a quality controlled fit.
The most challenging organizational issue was
bringing different and separate departments and
political entities together to create a united
front to obtain the necessary funding and support
for the project. This took over a year to
accomplish. By interlocal agreement, the Property
Appraiser's office, under the direction of the
Director of GIS, became the Project Management
Agency for the development of the base and parcel
data. Under a directive from the Property
Appraiser and the County Administrator, the
Director of GIS established three GIS committees:
the Policy Committee, the Steering Committee, and
the Technical Committee. The Policy Committee is
concerned with securing the funding and overall
policy issues. The Steering Committee is
concerned with specific GIS direction and
developing data and applications. The Technical
Committee is concerned with the necessary
technical issues needed for the day to day
implementation and development of the program.
These Committees co-exist with a more loosely
organized relationship between the Property
Appraiser's office and each participating city.
This structure has proven to be productive in
obtaining the necessary equipment, software,
hardware, personnel, contracts, and funding to
support the goals and objectives that the Policy
Committee has established.
Our current GIS usages are parcel mapping, traffic
engineering, natural resources and drainage,
addressing, public information, comprehensive
planning. In the fourth quarter of 1996 the
County Property Appraiser will install the Public
Inquiry and Plotting capability, allowing the
public to access the GIS for viewing and plotting
sections, subdivisions, and parcels. Future plans
call for the use of lap-top computers in the field
by appraisers, public safety, and engineering
personnel. Applications have been planned for
roadway maintenance, production engineering,
development review, E911, human resources, parks
and recreation, and water utilities. Internet
access to view the data is also being evaluated.
In summary, the success of the GIS project is
based on the fact that it works in its most
practical sense for local government and for the
public. It is cost justified, with costs being
defrayed by several agencies working together.
The Property Appraiser is responsible to develop
the core system, and allows access to the data
over a local and wide area network, or, if
requested, will periodically make available the
most up to date information on tape for users not
on the high speed computer network. And for users
that may use a different GIS software, like the
City of Lakeland, a program is in place to
periodically send translated data to their
computer system.
With one responsible project management agency,
coordination is easier. With the GIS committees,
decisions are made on various levels to help
support and manage the implementation and usage of
the system. Project deliverables are kept on
schedule, with specific delivery items that are of
immediate use. Under the leadership of the Polk
County Property Appraiser, Polk County is well on
its way to completing a successful GIS system by
eliminating redundant data collection, and
providing more effective and efficient service to
the public.