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 Shares It?

Some local, some state, some not at all.  Remember when Google first started and the one liner about them was “if you have it, we want it”.  That’s the story for parcel data too.

There are lots and lots of cities and counties that share parcel data with attribution on a regular or periodic basis.  Some update continuously others provide quarterly or annual updates.  A recent survey of parcel producers found there are approximately 6,500 parcel producers (cities, towns and counties) in the US (see Parcel Data - Who Builds it) and of these nearly 70% provided at least viewer or REST Service access to their data and a smaller percentage (around 50%) provided free download and/or open data access. Those that do provide open and/or downloadable access cover almost 80% of the US population and parcel count.

As awesome as digital parcel data are there are certainly understandable reasons why all parcel data is not shared for everyone to have.

The vendor made me do it or proprietary formats - It’s not the mapping formats, it’s the attributes.  Many local governments are tied into real estate tax system (or CAMA) software that has the attributes locked up in either a difficult to extract or expensive to extract data structure.  In a few rare cases the mapping and attribution is managed by outsourcing and the local government doesn’t even own it’s own maps or data.

Once bitten, twice shy - Many local governments have experienced sharing their data with an application or a customer only to be criticized because the supplied parcel data did not meet expectations.   As examples “Why doesn’t this data indicate which homes are owner occupied and which are rented?” “I wanted to see a recent inspection on condition of the structures, where is that information?” I checked this data against my iPhone and the coordinates you have are wrong, I am calling my councilman.” “Where is the mortgage amount in this data set?”  Many of the concerns downstream users have can be explained if the data producer has a chance and if the recipient wants to understand.  Unfortunately, there are too many instances where the criticism gets widely distributed and the explanation (metadata) not so much. 

Show me the money - This has several variants including - We paid good money for this; we are not going to give it away and I need this revenue to fund my office.  These are all, well mostly all, good reasons.  There are many jurisdictions that run short of allocations and automation is not enough to make up the shortfall.  In the Parcel Dial Tone, I mentioned the need for more rural counties and under budgeted offices in particular to charge for data.  Sadly data sales are not likely to be a sustainable revenue stream.  It’s just the way it is.  Consider the path imagery and addresses and elevation and building footprints and so many other data sets have taken.  As technology advances the data becomes more widely and more freely available.  This is not ridicule or undervalue the resource needs of local assessors and parcel mappers.  The needs are real; we just need to find more sustainable and effective funding sources.

It’s mine - Much like parenting sometimes it just comes down to you can’t go to the movies because I say so. Period.  Sometimes this rational is clothed in privacy concerns or “what are you going to do with it?” concerns (see once bitten, twice shy).  Sometimes it’s just that so much personal dedication and commitment has been put into the data, it’s hard to let it go. It’s hard to not take ownership of it.  I have always thought that parcel data is personal.  It’s the most personal of all locally maintained data sets.  The data producer’s fingerprints are all over this data set and having a sense of ownership is certainly understandable.

Who shares parcel data? The most recent detectable trend is more and more parcel producers are sharing, especially cities, lots of cities.  

Parcel Data – Who Builds It?

Local governments mostly.  And often the most local government meaning the town, city, township, or county.  In some cases, the state prepares parcel data on behalf of the local government. Parcels and addresses are the most local government data.  Constructed closest to the citizen. 

In addition to the obvious tax assessment, real estate billing, and real estate tax management, parcels, generally tax parcels, are used many local functions like permitting, land use planning, zoning management, land banks, public lands management, and many many more. 

Parcel data aggregation combines data from multiple data maintainers into single standardized data sets.  Most parcel data aggregation occurs at state or regional government levels.  There are also many cases where counties (and their equivalents) are aggregating digital parcel data from cities and towns).  County level aggregation often requires maintaining and reconciling common boundaries for a seamless representation.  Regional and state level aggregation is less likely to reconcile common boundaries. There is an increasing trend for states to build standardized aggregated parcel data sets to support statewide value equalization, state disaster response and recovery functions, broadband access management, and many other cross jurisdictional business needs.

An inventory map of the local governments that have digital parcel maps can be found at this link (http://fairview-industries.com/USParcelData/USParcelData.html).  This is a voluntarily maintained inventory and is not positively complete and accurate but it is a good indication that about 90 % of the 150 million parcels in the US have been mapped into a GIS or automated mapping software of some type.

That is just the mapping.  Real estate valuation and tax attributes are 100% automated at some level.  Yes, there are still jurisdictions that have hand written, hardcopy individual property assessment cards, but a recent national inventory did not find any jurisdiction that hand generated real estate tax bills.  Every jurisdiction was covered by or represented in a Computer Aided Mass Appraisal (CAMA) or similarly functioning system even if the most local officials did not have the software.

The attribute data are by no means standard.  Similar attributes are named and structured differently, data are collected or entered at different times, the basis of the attributes values, and extent of attribution vary greatly.  Adding to the variation, there are well over 75 software vendors each with local installation customizations.

Local governments build parcel data and each one builds it and maintains it uniquely. 

Authoritative Cadastral Data

Unlike other spatial data (hydrography, topography, orthoimagery, etc), cadastral data defines rights and interests in land. Cadastral data are also unique because it is created and maintained by over 4,000 separate entities across the country.

The vision for the National Spatial Data Infrastructure (NSDI) and the National Cadastre within the NSDI is to have a single source of authoritative cadastral data that is controlled and managed by designated data stewards. Access to this data is facilitated by compiling and integrating the data into trusted data sources at state or regional levels. This will reduce duplication of effort and assure that the best available information is used in decision-making.

Cadastral data includes assessment records that support the real estate property tax system, recorded land documents such as deeds and mortgages, indices and summaries of this data such as a grantor-grantee and tract indexes, and survey information captured in plats and surveys.

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.

Trusted data describes data sets that are published by someone other than the authoritative source and is often the compilation of multiple sources of authoritative data. It is “trusted” because there is an “official process” for compiling the data from authoritative sources and the limitations, currency and attributes are known. The data are often formatted into a standardized form and linkages to the originating source are provided with the data. This trusted source is recognized by the authoritative source as an “official” publisher of this subset. Typically a trusted source is established to integrate data from multiple jurisdictions and to compile it into a standard format. This trusted data is adequate, convenient and cost effective for users who need a regional view and have to deal with multiple sources of data, but there is an understanding of the necessity when final decisions are being made, particularly about rights and interests of specific properties, that the user must go to an authoritative source and acquire authoritative data directly to ensure that they have the most current an accurate data.

Data stewards have the responsibility to organize, collect, maintain and provide data. Data stewards are those closest to the data creation, they have recognized expertise in the field and follow professional standards.

When there is not a single source for data, such as nationwide assessment data which has over 4,000 local government sources, and the effort to acquire authoritative data from individual authoritative sources is impractical, then it is reasonable to acquire trusted data from a trusted source.

All cadastral data collections that do not come from authoritative or trusted sources are “unofficial” or “shadow” copies whose value degrades over time relative to the rate of updates to the authoritative data. Unofficial data is often duplicative and creates redundancy by re-publishing data that are already available from a trusted source. Unofficial sources create confusion among the general consuming public by providing un-maintained duplicative data and “unofficial” parcel-like data sets that can unexpectedly harm or damage property rights with inaccurate out of date information.

Recognizing the importance of authoritative sources for authoritative cadastral data that may be provided through a trusted source will be essential to protect individual land rights, to support local governments and other parcel producers in their authorized role of data stewards and to ensure that the user community has the best available and most current cadastral information.

The FGDC Subcommittee for Cadastral Data, following the directives in OMB Circular A-16, has developed a series of documents over the past ten years that describe the concepts and polices related to the creation, use and publication of cadastral data. There is more information on authoritative and trusted sources for cadastral and data stewards for various components of cadastral data at the FGDC Subcommittee’s publication site (http://www.nationalcad.org)