By now, most GIS professionals interested in maintaining Land Records in GIS have heard of the ESRI Parcel Fabric but, considering the adoption rate I've been witnessing, many are still reluctant to fully adopt the concept and implementation. Many of you have heard me speak in the past few years about the benefits and challenges involved in moving your data to the Parcel Fabric. Future posts will discuss options for implementing the Parcel Fabric, but in this post, I will attempt something a little less challenging and introduce the various components of the Parcel Fabric.
Conceptual Data Model - The Design
Within the Parcel Fabric, features are defined by the "type" of polygon they represent. For example there are: Legal definitions of how land is divided such as the Public Land Survey System Townships, Sections, Quarter Section, Special Surveys, or by the legal subdivisions of the land such as subdivisions or condominiums and the interior subdivisions inside these legal entities (lots), or they are defined by "types" of interests in the land such as: taxable interests, ownership interests and other partial interests such as easements or leasehold interests. By far, this approach is the most comprehensive attempt to map all components of land interests in decades and the initial concept can be found in GIS and Land Records by Nancy von Meyers of Fairview Industries. This approach provides a logical place for all types of interests in land and tracks how the land is defined and ownership of interests in that land.
Logical Data Model - The Way it Works in ArcGIS
The Parcel Fabric is a complete land records data model that consists of several standard feature classes in a geodatabase that are "tied together" similar to a geometric network. When I first introduce the structure to my students, I almost always describe the Parcel Fabric as a "geometric network for polygons."
As a matter of fact, the entire Parcel Fabric data model revolves around the polygon as the primary geometry with all other information being related to that polygon geometry. This is very different from the cartographic data model that many organizations are still using where everything revolves around lines.
The Parcel Fabric data model, and specifically the Local Government Information Model, provides the polygon feature class as the primary record and then has corresponding lines that define that polygon and corners that define how those lines are joined to one another. It also includes a table to store information about the document that created the polygon (the plan table) and a feature class to store control points that define the spatial locations of the points relative to the surface of the Earth.
Local Government Information Model (LGIM) - The Standardization
The Local Government Information Model is ESRI's attempt to develop and promote a standardized data model to allow greater consistency across organizations sharing similar needs, but also having that standardized data model adopted to allow the development of enhanced and complex maintenance functions that make Land Records maintenance more efficient. In other words, by having everyone, or at least those organizations seeking more efficiency, adopt the LGIM, ESRI can develop sophisticated tools that allow us to perform standard maintenance tasks in fewer steps with fewer mistakes.
Tools - Let's Make it Easier
While I plan on having many posts directly relating to specifics of the Tools available for the Parcel Fabric, I can say that, with each new release of ArcGIS for Desktop, ESRI continues to improve the quality of the parcel editing tools, making them more and more efficient and making the job of the Parcel Mapper easier.
For example, some of the new tools included in the Parcel Editor functions in ArcGIS for Desktop can do things such as: take an existing parcel polygon, calculate a portion of that "parent" parcel, calculate and input all lines required for that portion and the parent parcel, store and create two new parcels and mark the existing parcel historic so we can go back and see what the parcel looked like before we perfumed that split. ESRI has also integrated these tools into Automated Parcel Editing Workflows that will identify and guide you through step involved in parcel maintenance. These workflows are a great first step in making the software easier to use and, while still needing refinement, you can see the commitment of ESRI towards building a complete solution for Parcel Maintenance.
These tools are only available once you adopt and implement the Parcel Fabric as your parcel maintenance solution. The LGIM and the enhanced parcel maintenance tools go hand in hand and make the maintenance of land records better.
Hopefully this short post helps with your understanding of the Parcel Fabric, or maybe just piqued your interest to learn more. If you have questions or comments, please share them below.