Parcel
Identifiers
A
Review of Standards and Practice
There are many systems and specifications for parcel identifiers. Most of these are associated with real estate
tax systems but there are also parcel ownership identifiers, real estate
improvement identifiers land transaction identifiers, generally on publicly
managed lands. This document reviews
some of the recent standards and some best practices for parcel identifiers.
Standards
The International Association of Assessing Officers (IAAO) has an
established standard for cadastral mapping and parcel identification systems.
This standard was revised in January 2012.
This standard provides recommendations
on the development and maintenance of digital cadastral assessment maps, parcel
data layers in a geographic information system, and parcel identifiers.[1]
IAAO is one of the standard making bodies for property assessment and
valuation. The IAAO recognized the importance of parcel numbers across
municipalities and developed a set of core recommendations for creating these
PINs.
· Compliance with Standards - The PIN should conform to
defined standards including national, state and local standards.
· Uniqueness – The most important aspect of the PIN is
that it be unique.
· Permanence – PINs should be permanent and only be
changed in extreme circumstance.
· Simplicity and Ease of Use – PINs should be as short
as possible, uncomplicated, and easily understood.
· Ease of Maintenance – The PIN should be easily
maintained and accommodate changes such as a split or merge operation.
· Flexibility – The PIN should also be flexible to
accommodate not just land but multi-family dwellings, sub surface rights,
leases, etc.
IAAO defines a parcel, a feature that is assigned a
PIN, as a
single, discrete piece of land having defined physical boundaries and capable of being separately
conveyed.
In another national standards effort, Mortgage
Industry Standards Maintenance Organization (MISMO)[2]
has formed a working group to develop a national parcel identification system.
MISMO was formerly a part of the Mortgage Electronic Registration Systems
(MERS) and has recently been brought under the Mortgage Bankers Association
(MBA). The
mortgage industry currently uses a combination of postal addresses, legal
descriptions, assessor parcel numbers and geospatial coordinates to track
homes. The MISMO Development Working Group (DWG) will focus on the development
of universally accepted system parcel identification for the future mortgage
market.
There is no universal standard for identifying a
property, resulting in greater risk for mistakes and fraud. This proposed DWG
seeks to bring together industry representatives to talk about current
challenges, and possible enhancements for improving data standards in the realm
of property location definition, verification and best practices. [3]
Another standard’s body is the Property Records Industry
Association (PRIA), which was founded on the concept that government and
business can work together to address issues of common concern in the world of
property transactions.[4] PRIA has established a GIS working group that
has the following charge.
A recent estimate shows
approximately 70% of all local governments have implemented some form of GIS.
Yet in many cases GIS is not integrated with the recording office. The
PRIA GIS Workgroup has been chartered to establish standards, procedures and
best practices for data exchange between GIS systems and land records systems.
This will allow the exchange of information while taking into account
performance, security, and revenue implications.
This group has not completed standards development but is
working toward a national parcel identification system that will allow linkage
between GIS features and source documents.
The FGDC Cadastral Data Content Standard and the core parcel
publication guidelines derived from that standard also calls for a nationally
unique parcel identifier. In the case of
the FGDC standard the national standard leaves the local parcel identifier in
tact and appends the jurisdictions Federal Information Processing System (FIPS)
code to the front of the local identifier.
The FIPS code assigned is determined from the supplying data steward.
The Open Standards Consortium for Real Estate
(OSCRE) statement of purpose is “effective open standards are crucial
for sharing information across boundaries and for systems that more easily
interconnect. Standards play a key role
in innovation by giving businesses more choice in the software they use by
reducing vendor lock-in and reduce the cost of IT by enabling a more
competitive and diverse market.”[5]
OSCRE is a more international standards
body than the others. In 2005 DoD adopted an agency wide real property unique
identifier (RPUID) that was endorsed by OSCRE as a commercial best practice.[6] The DoD’s RPUID is assigned to structures
rather than land. Every DoD building and structure
is assigned a single number for its entire lifecycle. RPUIDs are tracked
centrally in a registry and any authorized system in DoD can obtain information
about a building by using the RPUID and web services to check the registry.
Each of the standards bodies has a slightly different need for a
national identifier. The activities and
lessons learned from these standards organizations provide guidance on
developing a parcel identification system.
One of the most important lessons seen throughout all of these standards
organizations is to complete and unambiguous definitions of the feature being
identified. MISMO is focused on
features that are identified in mortgage and loan documents, IAAO is focused on
features that are assessed or taxed, PRIA is focused on connecting land
descriptions to conveyance and other recorded documents, FGDC Cadastral
Subcommittee is focused on maintaining the data steward’s identification number
while allowing for national uniqueness, and OSCRE is focused on identifiers in
the system architecture and business processes.
DoD’s implementation focused on buildings and structures.
Public Lands
None of the existing standards reviewed specifically address how public
lands (non-taxable from a local government perspective) are assigned a parcel
identifier and what defines the extent of the publically managed parcel. In some areas of the public domain lands
there are vast areas that have neither a survey nor a case transaction. In these cases what is the best method for
assigning a unique identifier to the land area that will define and relate to
the land in a meaningful way and also be maintainable over time. Should every permit
or transaction generate a new parcel identifier or should the parcel identifier
be based only on the underlying land description and land survey?
Two federal land management agencies, the Forest Service (FS) and the
Fish and Wildland Service (FWS), currently use parcel identifiers. In the FS system a master geodatabase is
stored in a centralized location in Kansas City and is accessed through
Citrix. The updates are in real time
using Oracle Spatial and the geodatabase is not versioned. FS uses FME scripting to translate the
production data into the publication data sets.
The enterprise data warehouse supports generating publication data and
web-based services to support the decision support needs of the FS. The
publication database is designed to support regular reporting needs such as the
Land Area Report (LAR). The original FS withdrawal is assigned a parcel number
and subsequent acquisitions or withdrawal actions are added with an assigned
separate parcel identifier. FWS does not
maintain a BLM Case Serial number for acquisitions or withdrawals but does have
a nationally internal unique parcel number for all parcels. The original defined acquisition
authorization area has a parcel identifier, as do all subsequent acquisitions
with each conveyance or land ownership change assigned a new parcel
identifier. There was a large
reconciliation project that worked through the FWS Lands database and the GIS
to finalize and establish the unique parcel identifier across all systems.
In the Montana Cadastral System the publicly managed lands did not have
a parcel identifier at the start because these lands were exempt from property
tax systems. But as the CAMA and GIS
grew the need for an identifier for public lands (state, federal and county
managed lands) became more apparent.
Attributes about the management agency and any actions on the lands had
to be linked to the spatial feature in the GIS.
The publicly managed lands, including federally managed lands, are
assigned a parcel identifier that is in part a geocode that identifies the county,
the PLSS Township, section and if applicable, quarter section. No parcel is larger than a section. Federal lands smaller than a section are
identified to either the quarter section and then further divisions according
to the state DOR system for tagging areas smaller than a quarter section.
This system has worked well in Montana and although it is not
synchronized with BLM records, as parcels are exchanged or apparent parcel
configurations are changed, parcel identifiers are updated. Montana recognized that the BLM often has a
more granular definition of their land based on case actions. Although desired, the state does not have a
link to records in LR2000 that would facilitate a more complete representation
of land transactions on federally managed lands in the Montana Cadastral System.
State Systems
Many state departments of revenue or taxation have some guidance on tax
parcel identification; Florida, North Carolina, and Utah are three examples. The state guidelines may or may not be
enforced and there is significant variation in local governments even with
state guidelines. Utah’s state parcel
identification guidelines provide three system or methods for parcel
identification and summarizes these three commonly used systems.[7]
Proper identification of properties is essential to accurate
valuation. A parcel identification system provides a method for referencing
land parcels or data associated with parcels, using a number or code instead of
a complete legal description.
It
is important that the parcel numbering system allow the user to locate the
parcel by means of the unique number. There are three kinds of numbering
systems, which are suitable for this purpose.
Map-base
In
a map-base system, the first number sequence is assigned to a map, the second
number sequence to a block or other organized map division, and the last to the
individual parcel. An alternative map-base system is called a book-page system.
The first number sequence is assigned to a book of maps, the second number
sequence to a map page within the book, and the third to a parcel on the map.
Government
Survey
The
government survey takes for a base the existing land survey system of townships
and ranges. The numbering sequences correlate with sections, quarter sections
and other such subdivisions as necessary until the last number sequence, which
refers to the individual parcel.
Geographic
Coordinate Code (Geocode)
The geocode system is typically used on a computerized
(GIS) system where the approximate center (paracentroid) of each parcel is
identified. The parcel is numbered based on its x (east-west) location and y
(north-south) location. Although the geocode system is accurate and quick, the
parcel numbers do not tie directly to any given map or block. When a GIS
mapping system is utilized, coordination with the AGRC is required to
facilitate uniformity, data transfer, numbering schemes and formats used in
parcel identification.
Local Systems
There are almost as many variations in local parcel identification
systems as there are local systems.
Although the emergence of national CAMA vendors such as Thomson Reuters, Tyler Technologies, and Orion have reduced
the number of local variations as these system each enforce consistent parcel
identification requirements. It is not uncommon for a county to maintain
several parcel identifiers with municipalities, the assessor, the treasurer and
the planning agency each assigning a separate identifier.
From a national perspective organizations that consume parcel data from
many local jurisdictions especially across state lines are often confused about
the formats and content of the parcel identifier. While it is often possible to make each
county’s parcel identifier unique by appending a local jurisdiction code to the
front of the number, the structure of the parcel identifier, the content,
special characters such as dashes or periods, and inconsistent usage such as
the reuse of parcel numbers creates uncertainty when other data is connected to
the local parcel data sets. This
typically happens with value added commercial data providers but can also occur
in many other situations when the parcel data is used as base data for an
application or to support a business need.
Conclusion
The basis for the identification number, whether it is computer
generated or based on the parcel location or the parcel characteristics, was
not found to be as critical for success, as the following.
(1) The
parcel being identified is well defined, recognized, and unambiguous. For example are parcel identifiers attached
to ownership parcels or to tax parcels?
(2) The
identification system, whether a number or intelligent key, must be unique
across the entire system, never duplicated, and be easily generated.
(3) The
parcel identification remains unchanged throughout the parcel’s life cycle, such
as if the geometry of the parcel does not change than the parcel number should
not change, and
(4) The
parcel identifier must be able to be used to link to related records and
documents.
[2] MISMO®, the leading technology standards development body
for the residential and commercial real estate finance industries, is a wholly
owned subsidiary of the Mortgage Bankers Association. From http://www.mismo.org last accessed 10-2-2012.
[3] http://www.mismo.org/files/PressReleases/NewDWGPressRelease9_14_2012.pdf, last accessed 10-2-2012.
