The Parcel Data Model - The Ownership Types

Last week we looked at the Parcel Data Model, a comprehensive way to store and manage information about Land Records that divides the layers of data, or "Types" into two distinct classes: those types that define how the lands are "partitioned or divided" and those types that define the various forms of land "ownership".  Let's continue our review by exploring the Ownership types.

The Ownership "Bundle of Rights"

The Ownership "Bundle of Rights"

Ownership Types

The remaining polygon types within the Parcel Data Model cover the various ways in which land can be owned. The following discussion is not intended to be a treatise on land ownership in the United States, but a generalized discussion of how these ownerships are stored with the Parcel Data Model.

Ownership interests within the United States are not a single right, but are often referred to as a "Bundle of Rights." As such, one can possess a a majority of the rights (this is often referred to as "fee simple ownership", or a single temporary or permanent right.

Type 7 - Right to Pay Taxes - Tax Parcels

The first ownership type stored in the Parcel Data Model is intended to store and manage information about the "right to pay taxes". This is the polygon type most often mapped and maintained by Property Appraisers (Assessors) offices through the country. One general misconception by the general public equates these parcels to "ownership" of the parcels, without realizing these polygons represent the tax obligation, or those properties on which ad valorum taxes are paid and may not represent true ownership.  This is especially true where there are long term lease interests that contractually have been obligated to pay the taxes on this lands under lease (think shopping malls, etc.)

Type 8 - Fee Simple Ownership - Ownership Parcels

The second ownership type, and the eighth polygon type in the Parcel Data Model is intended to store and manage Fee Simple Ownership. Specifically, this is often used to map and maintain surface rights and neither subsurface rights such as minerals or gas nor air space rights. While most agencies at the moment do not maintain information on these ownerships, I envision a time when it will become increasingly important.

Type 9 - Less than Fee Simple Ownership - Encumbrances

The next ownership type is that of Encumbrances. Black's Law defines encumbrances as the right of use over the property by another. In this sense, any use of the property by anyone other than the fee simple landowner can be considered an encumbrance. Encumbrances are often limitations of the use of the land by the fee simple owner. Various types of encumbrances include: rights of way or road easements, drainage or flowage easements, conservation easements, fishing easements, grazing rights or utility easements.

Type 10 - Separated Rights

The next ownership type is that of Separated Rights. As noted in the Cadastral Data Content Standard for the National Spatial Data Infrastructure: separated rights are rights and interests in land ownership that can be disconnected from the primary or fee simple surface ownership.  For example, mineral and oil rights are often separated from the surface ownership.

Type 11 - Other Rights

The final polygon type is intended to cover those other ownership interests that do not fit into any of the other polygon types.


Over the past two blog posts we have examined the various polygon "Types" in the Parcel Data Model used by the ArcGIS Parcel Editing Solution (formerly referred to as the Parcel Fabric.) I hope this helps you understand the manner in which the Parcel Data Model is used.



Curves in the Parcel Fabric

There are many ways in which the Parcel Fabric differs from our current mapping concept, some of them are obvious, such as the tools we use and the way we store land records data. But there are also subtle differences that we need to understand to make the most of the Parcel Fabric - We need to especially recognize that the Parcel Fabric stores curves differently.

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Feature Class Curves

Within a standard feature class, the curve is a variation on a single line vector. Albeit, the curved line has specific properties that define the amount that the curve is "bent". In fact, when we interact with the curve using the standard editing tools, we are actually just changing those specific properties that define the curvature.  

Because of the way the curve (arc) is stored, there are many tools in ArcGIS to help you define those specific properties to cause a curve to pass through start, middle and end points (arc function) or through specific endpoints (endpoint arc function), tangent to a previous course (tangent arc) or even a bezier curve (bezier). 

A Curve as defined in the Parcel Fabric

A Curve as defined in the Parcel Fabric


Parcel Fabric Curves

However, within the Parcel Fabric, curves are constructed and stored as geometric definitions and the actual point of curvature (PC), point of termination (PT), the radius point (RP) and radius lines are constructed and stored. These points and lines define how the curve is drawn. Interestingly, because the actual arc of the curve is constructed within the Parcel Fabric, you cannot join or link to the actual curve - you must join or link to the defined points (Point of Curvature, Point of Termination or Radius Point.)

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The implications of this difference in the way curves are stored are important to understand. For example, if two curves are stored in the Parcel Fabric and are supposed to be concentric and there are any variations in the location or geometry stored with those curves, they will create differing points and will not be drawn as concentric. Instead, there will be two different points stored as illustrated to the right. In this example, the two curves were stored and there was a difference in the radius length stored ( this was not necessarily an error, this difference could have been simply a rounding error on the original information.) But, having these two points stored as different values will result in the curves not being drawn concentrically. 

To remedy this issue, you must force those two points to be stored as one.  To accomplish this, you use the Mean Points tool in the Parcel Editor Toolbar. 

The Mean Points tool in the Parcel Editor Toolbar

The Mean Points tool in the Parcel Editor Toolbar

Dragging a box around the points to be "meaned" (averaged) will move the points together and result in having the curves drawn as concentric, even if they have differing COGO information stored in their respective geometries.

Remember, within the Parcel Fabric, the actual joins to points and linepoints is critical to how your data is drawn.  Be sure to check to make sure the points are joined correctly and that all three points in the curve (PC, PT and RP) are correct.