Color by Number
Charlotte County in Florida, established in 1921, covers an area of approximately 859 square miles (2,225 km2) and is located on Florida’s southwest Gulf Coast. Situated on and around Charlotte Harbor, the county was dealt a significant blow by Hurricane Charley in 2004. However, it has since rebounded from that natural disaster and continues to experience considerable growth.
To aid in the management of land records that go along with that growth, the county had begun developing a GIS program intended to support the needs and operations of many departments within its local government enterprise. Like many other jurisdictions, Charlotte County had initiated manual and CAD-based procedures many years ago for mapping land records updates. However, increased user demand and other information deployments were putting a strain on its system, which lacked the enhancements available with newer technology. “While the county used other CAD platforms for performing certain tasks (such as parcel mapping), other departments were still using manual methods for updating geographic information,” explains Jeff Reese, information services manager for Charlotte County.
The County Zoning Office, key users of GIS technology, already made use of Esri shapefiles, but the administrative boundaries within these data were often not aligned with the rest of the county’s geographic information. In fact, many of the county’s datasets were in a legacy Esri coverage model, and steps had already been taken to begin moving several of these into an Esri geodatabase. Charlotte County’s Property Appraiser’s Office was one department still using CAD and manual methods for updating geographic data, and the County MIS/GIS Office and a few other departments were using the data produced by the property appraiser. “A key objective for the MIS/GIS staff was to align the Property Appraiser’s Office on the same GIS platform as all other county departments so as to be fully supported by one enterprise geodatabase system,” Reese says.
With the advent of a coordinated plan for a new GIS program, the Property Appraiser’s Office and County MIS/GIS Office had already begun to explore new workflows for automating the creation and history of parcel numbers. However, three main challenges existed in managing a conversion of the property appraiser’s existing system to the county’s enterprise GIS:
• Dealing with an outdated data model,
• Reconciling inconsistent/complex parcel numbering, and
• Improving the accuracy of the GIS data.
To address these issues, Sidwell suggested several improvements to the cadastral data model. First, in an effort not only to maintain but also to increase functionality and ease of use, the firm recommended that Charlotte County significantly overhaul its system by implementing a tagged/multiple feature data model--an innovative model used specifically for maintaining cadastral (parcel) data in an Esri geodatabase. “Cadastral data are unique in that multiple features can occupy the same geographic location (i.e., coincident boundaries),” explains Tom Ricker, GISP, director of project management for Sidwell. “This data model leverages a linear-based structure for efficient entry and processing of land records information. Use of the tagged data model allows for expedient maintenance of multiple data layers, thereby ensuring that data are consistent and current.”
From the single spatial features and multiple cadastral feature assignments, other countywide datasets can be generated to support other GIS operations within the county, including spatial analysis, end user deployments and data sharing. One of the most time- and cost-saving aspects of this data model design is the assurance of coincident boundaries for all extracted lines and generated polygons.
By converting to an Esri geodatabase, the county has simplified its editing workflow with fewer layers to edit. In addition, it has introduced an inherent spatial relationship between the many layers maintained by several different offices and is now able to enforce business rules about the relationships between geographic and tabular data (see Figure 3).
To satisfy the county’s needs and support growth for decades to come, Sidwell also recommended a parcel numbering component as part of the project. All 220,000 real property parcels in the jurisdiction would be renumbered to reconcile the county’s existing parcel numbering system, which was complex and inconsistent. Based on the Public Land Survey System, the entire parcel numbering system for all real properties, including condominiums, was assigned a specific range of numbers, which are broken down in Figure 4.
Condominium properties also required special consideration; with approximately 13,987 such properties in the county, a solution was needed that would allow for easy identification, maintenance and growth. Condos were organized into groupings (see Figure 4) that make identifying these parcels easier. The method for geographically managing the condos was altered to account for multiple ownership and common areas.
In addition to the enhancements made to the data model and parcel numbering system, Sidwell worked with the county to make spatial adjustments to improve the position accuracy of the data. The county provided Sidwell with multiple control points with which to tie and adjust the data. These enhancements would further support the growth management needs of the property appraiser and the county as a whole.
As a final enhanced component of this project, Sidwell worked with the county to identify and migrate thousands of annotation and dimension elements from its existing CAD and hardcopy mapping systems into the newly defined geodatabase format. Within the data model, annotation subtypes were designed and populated with annotations and text from the various sources. These tasks provided the county with more accurately placed linework and better representation of source information. “Internal county users and external businesses professionals using the county’s newly reworked parcel data now have better, more complete information to assist them with their daily operations and tasks,” Ricker says.
The county wanted all the subdivisions locked down and surrounding parcels adjusted to them. Charlotte defines its subdivisions using coordinate geometry (COGO) and felt comfortable with the accuracy; therefore, Sidwell placed a minimum average of nine control points per section upward to 50 points if needed. A total of 3,303 control points were placed to ensure the spatial adjustment was only adjusting the proper parcels. In all, 7,116 parcels were adjusted.
The county had significant mismatches between the parcel numbers in the GIS parcel layer and the computer-assisted mass appraisal (CAMA) system. The workflow analysis identified that duplicate entry of the PIN and other parcel-related data in multiple systems created the majority of the errors. To eliminate these errors, the county and Sidwell integrated the two systems.
Now, the county creates all parcels in Parcel Builder Administrator, developed by Sidwell, and populates the related parcel spatial data from the recorded document when the parcel is mapped. Once the quality control process is complete, the data are passed via SQL table (referred to as the “swap table”), and Charlotte County IT pulls the information into the county’s in-house system (RPInquiry) for the appraisal staff to post-process ownership information and values to the property.
During the course of the project, map maintenance needed to be suspended for several weeks to finish conversion of Charlotte County’s system from coverage to the geodatabase format and to fully populate the multiple features and renumber all the parcels within the jurisdiction’s tax roll. Upon delivery of the project data by Sidwell, the county’s mapping staff received specialized training from Sidwell’s project managers that enabled them to update the backlog of maintenance within a few days.
The county has also recognized benefits in the adoption of a new countywide parcel numbering system. “Our tax collector and our property appraiser love the new system because they can easily get the general location of a property based on the parcel number,” Reese says. “The whole concept is being perceived very well.”
The Sidwell Co. was honored with the 2010 MAPPS Geospatial Products and Services Excellence Award in the GIS/IT category for its work with Charlotte County. For more information about MAPPS, visit www.mapps.org.