Parcel Data - Authoritative Source and Fitness for Use

The authoritative source for parcel data depends on what type of parcel data.  For tax parcels, the most commonly aggregated and distributed data set, the real estate taxing authority that created them (see who builds parcel data) is the most widely accepted authoritative source. For legal survey boundaries, the land survey record is the authoritative source.  But do we really mean fitness for use?

Authority, authoritative, and authoritativeness always seem to trigger a fairly robust discussion, especially around cadastral data.  A few dictionary-based definitions may be a good starting point.  The following are gathered from various dictionaries and papers on this topic.

Authority and Authoritative - Authoritative is recognized as trustworthy, competent, reliable, and true.  Supported by an authority.  In the context of public agencies it is the legal responsibility provided by a legislative body to conduct business for the public good.

Official - A person invested with the authority of an office.

Authoritative Data – For publicly sourced data these are officially recognized data that can be certified by the public provider, such as a certified tax roll, and is provided by an authoritative source.

Authoritative Data Source – An information technology (IT) term used by system designers to identify a system process that assures the veracity of data sources. All geospatial data providers should follow these IT processes. The data may be original or it may come from one or more external sources all of which are validated for quality and accuracy.

Authoritative Source – An entity that is authorized by a legal authority to develop or manage data for a specific business purpose. The data this entity creates is authoritative data. Authoritative data comes directly from the creator or authoritative source. It is the most current and accurate and has been vetted according to official rules and policy. The data has a known accuracy and lineage and can be verified and certified by data stewards in the authoritative source. In some terminology this is termed the “primary” data source or the “official” data source.

Authorization – The result of an act by a legislative or executive body that declares or identifies an agency or organization as an authoritative source or grants the rights to an agency to act, such as an authorization to manage land or collect information.

Data Steward – An organization within an authoritative source that is charged with the collection and maintenance of authoritative data. The term data steward is often confounded with the term authoritative source. A data steward may be a designated point for the assembly and aggregation of data from authoritative sources.

Trusted Source and Trusted Data – A service provider or agency that publishes data from a number of authoritative sources. These publications are often compilations and subsets of the data from more than one authoritative source. It is “trusted” because there is an “official process” for compiling the data from authoritative sources and the limitations, currency, and attributes are known and documented.

In the discussions around a national parcel data set or national parcel data sources, It appears that a discussion and agreement on fitness for use, including some standard or consistent wording or perhaps even categories of fitness for use would come in handy.  We need to answer questions such as “are the values on this parcel from my local assessor and are they official or certified?” or “can I rely on these annexation boundaries as the official boundaries?” or “are these boundaries attached to their definitive source document?” Standard metadata templates include a field for describing intended use or use limitations.  Perhaps it is time to look at providing consistency for these fields.

Many local and state published data sets have a disclaimer that limit the liability of the publisher and provide some general fitness for use such as “not to be used for land transaction legal descriptions”.   A data publisher can never know all possible uses for a data set.  It is likely that some or most data sets will be misused.  Disclaimers try to limit the liability of the data producer if the data are put to some unintended or wholly inappropriate use or relied upon to support an application for which the data was never intended.  This is completely understandable.

As parcel data moves to more open formats and publication, perhaps this is a good time for the community to have some discussions and consensus on expected fitness for use.  This would be more exact and less misunderstood than using terms like authoritative or trusted. 

Parcel Data, Who Needs it

Just about everyone.  At a recent parcel gathering there was some discussion about re-discovering which federal agencies need parcel data. 

As our computing and analysis capability expands so does our need for more granular and more detailed information. An overview of the granularity of geographic units in the US shows the increasing density and decreasing size of the unit of land about which we can compile information.

50 states

3,200 counties or equivalents

40,000 functional governmental units

57,000 7 ½ minute quadrangles to cover continental US and Hawaii

66,000 Census tracts

3.8 million square miles in the US

11 million Census blocks

133 million residential housing units in the US

(5.6 million commercial buildings)

150 million parcels

324 million people in the US

Parcels are the logical division of land for compiling information about use, value, and ownership. And who and what agencies need to know about use, value, and ownership?  Almost every agency at some level needs this data.

In 2008 the Cadastral Subcommittee interviewed 30 federal agencies to ascertain their use of or need for locally produced parcel data and for the responding agencies 16 had a clear identified need.  (http://nationalcad.org/download/Federal_Agencies_-_final.pdf)

Since 2008 as agencies have become more familiar with the availability of more detailed information and the ability to use and analyze bigger data sets (think GIS big data) has arrived, the identified needs and uses for parcel data have grown.

And what information about parcels is needed?  Other than guarded concerns about personally identifiable information (PII) the basic information needs are as originally defined nearly a decade ago (http://nationalcad.org/download/CadNSDI-Version2-Documentation.zip) and include use, value, and ownership.  Several agencies have expanded data needs, typically in more defined areas, such as urban areas, commercial parks, wildland fire interface areas, or farm program participation parcels.  Some of the extended attributes in more focused areas include, rental or owner occupied, mortgage status, tax bill payment status, farm field activity, new building activity, structure condition, and commercial lease values. 

Defining which attributes to aggregate and what standard field names and attribute types to use are not barriers to building a national parcel dial tone.  These things have all been studied and are known well enough to start.  There will be updates of course.  How many times a year does your mobile phone provider update your operating system or connection parameters? 

Who needs parcels?  There are enough needs and uses that they should just be there.

PLSS CadNSDI – PLSS Special Surveys (Non-Rectangular Surveys)

This is the seventh of a series of documents that describe the contents of the PLSS CadNSDI data set.

PLSS Special Surveys are non-rectangular PLSS surveys.  They are deviations from the hierarchical rectangular surveys, are often defined or guided by provisions of legislation or authorities.  PLSS Special Surveys can “sit on top” of rectangular surveys or they may replace the rectangular surveys, creating a “hole” in the rectangular surveys.  In some cases a nominal rectangular survey is extended through the special surveys. 

The PLSS Special Surveys are not populated for the many eastern states data sets because at the time of the PLSS Surveys in the eastern states, the non-rectangular survey types had not been well established.  Also in the eastern states many of the non-PLSS areas were defined before the PLSS and were never in the public domain.  However, for purposes of transition in some of the eastern states PLSS the non-PLSS data are in the PLSS special surveys, this will update over time.

The other item of note in western states lands that were not in the public domain, such as Land Grants, is in the PLSS Special Surveys, but may transition to the Survey System feature class over time.

Each PLSS Special Survey feature or parcel has one survey type designation.  The PLSS Special Survey parcels may overlap.  The attributes for this feature are listed below.

FieldName	Type	Length	Description	AliasName
SURVID	String	50	Unique identifier for a PLSS Special Survey feature	Survey Identifier
SURVTYP	String	2	Code for the type of special survey.	Survey Type Code
SURVTYPTXT	String	50	Special survey type text description.	Survey Type Text
SURVNO	String	50	Special survey number or designator that identifies the special survey polygon	Survey Number
SURVSUF	String	5	Special survey suffix designation that makes the identification of the area unique.	Survey Suffix
SURVNOTE	String	50	Notes about the polygon feature that are important for using or understanding the feature. From the BLM SurvNotes are A = Approximate Acreage, C = Conflict or Questionable, D = Non-added Acreage, R = replaced	Survey Note
SURVDIV	String	50	The name or designation for any division of a PLSS Special Survey such as Lot in a Tract	Special Survey Division
SURVLAB	String	50	Label that is used for cartographic output or web display.	Survey Label
RECRDAREATX	String	20	The record or recorded area as a text field. This may include the units of area as well.	Record Area Text
RECRDAREANO	Double	8	The record or recorded area as a numeric field	Record Area Number
GISACRE	Double	8	The area of the feature in acres - computed from the GIS, this is not the record area.	GIS Area Acres
SOURCEREF	String	100	The reference to the source document could be a reference to a map or plat or a deed. This could include document type.	Source Doc Link or Reference
SOURCEDATE	Date	8	The date of the source document	Source Doc Date

The Survey Identifier is included in this feature but it is not fully populated in the data sets.  The original intent was to define a unique identifier for each special survey type, for example, most mineral surveys are uniquely numbered in the state and tracts are uniquely numbered within a PLSS Township, but this work was not completed in the initial data sets.

The domain of values for the PLSS Special Surveys is listed below.  These codes and types come from the BLM records system and are used to match the special survey parcel to federal records.  Over time it is expected that the description will be relied on much more than the codes.

Special Survey Type Code	Special Survey Type Description	Notes
2	Tract - Other than cadastral survey	A tract other than a cadastral survey tract is a piece of land that has the term tract as its designated land description on a survey document.  The lands will typically have a number, name, or letter designation.
D	Allotment Survey	Allotment Survey is an allocation of discretionary assignment of lands.
E	Metes and Bounds	Metes and bounds surveys are required to define the boundaries of irregular areas of land, which are not conformable to rectangular subdivisions. Metes and bounds PLSS Special Survey Types are coded as a metes and bound if no other non-rectangular survey type can be identified.
F	Farm Unit Survey	Farm Unit Survey
G	Land Grant	A Land Grant is a portion of land that was claimed and occupied by a foreign power or government prior to survey.  Land Grants are not the same as Grants of Land made to individuals prior to survey.  Neither the Land Grant nor Grants of Land are part of the PLSS as the rights to these lands existed prior to the public land survey.  The boundaries of these lands form a closing line for the PLSS surveys.
H	Homestead Entry	Homestead Entry is a metes and bounds survey made under the Homestead Act defining lands acquired under an entry for the purpose of acquiring title.  Homestead Entry Surveys are numbered sequentially and uniquely within a state.
I	Indian Interest	This code and domain was originally Indian Allotment but has been expanded in the standard domains to include all Indian Interest lands including allotments, reservations, and other lands.
J	Small Tract, Small Holding Claim	The survey made to delineate the tracts differs from a townsite survey in that it normally follows a pattern of progression subdivision down to the desired lot sizes without block designations or the segregation of streets and alleys. Regulations provide for reserving rights-of-way in the patents or leases.
M	Mineral Survey	A Mineral Survey is a lode claim, placer claim, or mill site established to mark the extent of public lands claimed for the development of minerals and intending to become a private interest.  Not all mineral surveys complete to a patent and those that do not complete are reverted back to federal ownership in most cases.
N	Townsite Survey	There are many provisions for the executive withdrawal of public lands for townsite purposes. A townsite survey is a survey made within one or more regular units of the township subdivision by which the land is divided into blocks, streets, and alleys as a basis for the disposal of title in village or town lots.
K	Townsite Block	A Townsite Block is a block within a townsite.  The Townsite Block needs the townsite designation to uniquely identify it.
Y	Townsite Outlot	A Townsite Outlot is a lot designated for public or community use within a townsite.
P	BLM Parcel	BLM Parcel
Q	Donation Land Claim	Donation Land Claims are portions of land that are 160 or 320 acres in size granted under the Donation Land Act of 1850 to citizens who resided in the Oregon Territory.  These are not the same as donation lands that were public lands donated or granted as an incentive for construction, such as railroad donations.
S	United States Survey - Alaska Only	United States Surveys exist only in Alaska.  These are similar in form to Townsite Surveys and provide for the disposal of public lands for occupation and settlement.
T	Tract	A tract is portion of land that protects a bona fide right.  Tracts are metes and bounds surveys that define the perimeter of lands settled between the time of the plan of survey and the actual field survey.  Settlement occurred following the boundaries intended to be as defined in the rectangular survey but do not conform to the actual rectangular survey.  Tracts are always contained within a PLSS Township and PLSS Township lines encompass the tracts.  Tracts are numbered within the Township taking the next highest number available after the highest section number.
X	Exchange	An exchange survey is a portion of land that has been described to support the exchange of private lands and public lands.  These are metes and bounds surveys.

The image below shows a cluster of mineral surveys and the surrounding rectangular lots and aliquot parts

 

Mineral Surveys and Rectangular Surveys

This same area without the special surveys appears to have “hole” in the second division.  This same “hole” will not be apparent in the Township and first division, at least for the mineral surveys.

 

"Hole" in Rectangular Survey

In other cases the non-rectangular surveys will sit “one top” of the rectangular surveys and the rectangular portions will continue under the special surveys.

 

Rectangular Areas Under Special Survey

The image below shows a Tracts and PLSS first divisions (Sections).

 

Tracts and Sections

The Tracts are non-rectangular parcels that typically start with number 37 in a township to distinguish them from sections.  Technically, Tracts are metes and bounds surveys that delineated lands that have an established right established prior to the rectangular survey typically by occupation.  This occurs when the land was settled prior to survey and the occupants intended to occupy a section or other parcel of land described from an unsurveyed plat.  When surveyed measurements of the protected rights determined that the occupied land did not conform to the rectangular survey, a tract is defined.  By definition the tract is described by PLSS Township and the Tract number.  The PLSS Township boundary should encompass the outside boundary of the tract.  However, this can create a “notch” or “protrusion” on the township boundary and in some cases the theoretical township line is extended through the tract.  Tracts numbering begins with the number 37. In the image above Tracts 38 to 40 are PLSS special surveys. 

Another PLSS Special Survey is the Townsite, coded as special survey type N in BLM records.   The polygons labeled in the figure below as “K ##” are the Townsite blocks, special survey type code K in BLM records.  In the PLSS a Townsite survey is a special survey that divides the land into blocks, lots, streets, alleys, rights of way, and reservations forming land descriptions for the disposal of title.  The key word is disposal.  Townsites, through a variety of acts and authorities, are intended to pass the land from federal to private ownership.  However, there may be parts of Townsites that remain in federal ownership or are re-acquired back to federal ownership. 

 

Townsite Survey

In this case the roads (coded as Townsite survey) plus the Townsite blocks would form the complete Townsite survey. 

There are many other types of non-rectangular surveys in the public domain and each will have a designated authority and survey rules.  Not all special surveys are found in all states.  It is best to consult with the state BLM Office or the state data steward for special survey situations that are irregular or not clear in the PLSS CadNSDI data sets.