ESRI's Parcel Editing Solution (The Parcel Fabric)
The ArcGIS Parcel Editing Solution (the Parcel Fabric) is a revolution in Land Records management. For the first time, we can create, store and maintain all relevant information about Land Records in a single unified data structure and use tools optimized by ESRI to make parcel maintenance more efficient and less time consuming.
Prior to the Parcel Fabric, the best practice for parcel mapping was to keep the various structural elements defining the boundaries of parcels on separate layers, or feature classes, resulting in a great deal of effort and procedures to attempt to maintain the "topologic" integrity of the features on these layers. This approach resulted in separate polygon layers to define the area encompassed by the sections within the Public Land Survey System, and separate layers for recorded and unrecorded subdivisions, block, lots, tax parcels and easements.
In addition to the polygon layers, each of these layers required a corresponding line layer to define and store information about the boundaries for each of these elements. These layers, while implicitly connected to one another, provided no easy way to manage the lines and polygons as cohesive entities - workflows had to be developed to handle this. This means that, even if you possessed a good GIS database of parcels, if you do not have mapping personnel who are following tested procedures for mapping and maintaining the parcels; you may be depreciating the quality of the stored data.
Weaknesses of our Current Data Models
While this layer based approach provides a logical way to capture and store information about the elements that make up and define parcels, and the structure is relatively simple to understand, this approach has many weaknesses: there is no easy way to associate the boundary lines with the polygons they define. In addition, the vertex coordinates for the lines and polygons are the sole elements defining the spatial position of the parcels and their corresponding boundary lines. No real information about how they relate to adjacent parcels is stored in the database. This causes a major issue when one attempts to perform maintenance on any parcel that includes upgrading or changing the geometry of the parcel, such as, when introducing more accurate information collected from a survey or new subdivision.
The Parcel Editing Solution ( the Parcel Fabric) Data Structure
ESRI’s new parcel editing solution, (the Parcel Fabric), solves these problems by using a database structure that understands every line that is associated with every polygon, even those lines that do not define the boundary but are used to define the location such as the lines from “Point of Commencement” to the “Point of Beginning” of a parcel described by metes and bounds or the lines that define how the boundary of a subdivision is linked to the sections in the Public Land Survey System. In addition, the Parcel Fabric stores all information captured from the source document, including dimensions, bearings, mathematical closure, and adjustments applied to the parcel when created. It also explicitly stores links to adjacent parcels and polygons on other layers to define how the fabric is interconnected. This “joining”, or linking, of adjacent parcels allows the fabric to understand how to apply upgrades to the location of physical elements such as PLSS section corners or new survey data without destroying the geometric integrity of the parcel.
Because of the integration of this ancillary joining information into the data structure, every parcel stored in the database remembers how it is supposed to relate to adjoining parcels and can be upgraded without requiring a “remapping” of the adjoining parcels. This alone provides for on-going sustainability of the data into the future as more and more information is collected, or made available, to the Property Appraiser’s office. In addition, when large areas of parcels are adjusted, the individual parcels retain their relationship with adjoining parcels and adjust according to these joined relationships.
Who should be using the Parcel Editing Solution ( the Parcel Fabric)?
The Parcel Fabric is maintenance component ESRI’s complete solution to Land Records Management, providing a complete data model built on best practices, together with new maintenance tools that work directly against this data model. This complete maintenance solution is optimized for those individuals responsible for the creation and maintenance of Parcels. If properly implemented, all other users of Parcel Data see no difference in the data structure with which they view or interact. In other words, no one except the Parcel Mappers are required to convert to this new data model and all other existing systems can remain unaffected.
Once your conversion is complete, you will have one set of data stored in the Parcel Fabric that is maintained using this very rich set of tools and structural rules to keep track and store the information important for maintenance and parcel definition and everyone else will have a separate set of the data that is stored in a simple feature class structure that is optimized for display and analysis speed.
How Does the Parcel Fabric differ from my Current Data Model in Defining a Parcel?
This is perhaps the most interesting component of the Parcel Fabric. In our existing data models, the individual parcels were defined by the coordinate values assigned to the vertices of their polygons. Lines storing the boundary information were implicitly stored on top of these vertices, but there was never any real definitions of how a single polygons was related to an adjoining parcel other than these shared coordinate values on the vertices.
The Parcel Fabric changes this relationship. It stores the geometric definitions of the parcels, and then store linkages, or "join data links" that explicitly define how the parcels are related to each other. When data is first imported into the Parcel Fabric, the import routines examine the vertices coordinates and builds assumed linkages. From that point on, all parcel maintenance and parcel creation uses the "join" links to define how the parcels are displayed, adjusted and exported.
What is Involved in Converting My Data?
Converting your existing data model into a optimized Parcels Fabric, while somewhat similar to the conversion from coverages or shapefiles to a geodatabase, is conceptually simple: 1. Analyze your existing structure, 2. Preparing your existing data for conversion, 3. Setting up a Staging geodatabase for the conversion, 4. going through the process of importing your data into the staging geodatabase, 5. testing the imported data for completeness and consistency, 6. adding any missing attribution or features. However, since the Parcel Fabric is a radically different structure, you will need experienced help to guide you through this process avoiding the many mistakes you can make along the way. Finally, since your workflow will be different, you will also need help in developing efficient workflows with the new tools and software.
This is where Panda Consulting can help, contact us if you wish additional information.