October 2013

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Overview

MassGIS' Level 3 Assessors’ Parcel Mapping data set, containing property (land lot) boundaries and database information from each community's assessor, was developed through a competitive procurement funded by MassGIS.  Each community in the Commonwealth was bid on by one or more vendors and the unit of work awarded was a city or town.  The specification for this work was Level 3 of the MassGIS Digital Parcel Standard.  As of October 30, 2013, standardization of assessor parcel mapping for 350 of Massachusetts' 351 cities and towns has been completed (however, data for Boston is not part of this project). MassGIS is continuing the project with the objective of providing updated parcel data.

This layer replaces the legacy Level 0 and Level II parcels.

MassGIS has assembled information and resources for those interested in maintaining standardized parcel mapping.

Digital Parcel Standard, Level 3

The standard establishes requirements for how parcel boundaries are compiled. It also requires creating a few attributes in the TaxPar and OthLeg feature class polygons that are unique to the standard.  In addition, the standard requires that a minimum selection of information from the assessor's database be included in a separate database table that can be linked to the parcel polygons.  Finally, the standard establishes very high percentage requirements for what percentage of parcels link to an assessor tax list record and vice versa.

One of the primary objectives in developing Level 3 in Version 2.0 of the digital parcel standard was revising the data model to eliminate situations in which one tax listing links to more than one polygon on the assessor’s map.  Sustaining this approach will, ultimately, depend on embedding a unique parcel identifier from the standard (the LOC_ID attribute) directly in the assessor tax list database.  Conversations with the four primary assessing database software vendors in Massachusetts indicate that embedding the LOC_ID in this manner can be accommodated in their existing database structures.  It always has been necessary to link multiple tax listings with one polygon (the most common example being condominiums), and the standard continues to model that relationship.

The standard calls for data stored in an ESRI file geodatabase (fGDB) with three feature classes, a database table, and two look-up tables.  These are all briefly described below and full details can be found in the standard.  The components of the Level 3 fGDB are:

TaxPar Feature Class (“tax” parcels) – this feature class comprises polygons or multi-part polygons, each of which links to one or more assessor tax records (unless it is a feature for which a tax record has not been established, i.e. public right-of-way, most water, etc…). In situations where two or more contiguous parcels have common ownership, the internal boundaries of these parcels have been removed, creating a single polygon corresponding to the tax listing that it represents.  Where two or more non-contiguous parcel polygons share common ownership, they have been converted to a multi-part polygon; each multi-part polygon links to one or more assessor tax listings.

OthLeg Feature Class - this feature class contains polygons representing other legal interests in land.  These other legal interests include representations of the “fee simple” property parcels that comprise the combined parcel polygons described above in the TaxPar feature class.  In addition, other legal interests in this feature class include various types of easements.

Misc Feature Class– this feature class contains map features from the assessor parcel maps needed to produce that tax map with the content that the assessor is used to seeing, such as water, wetlands, traffic islands, etc.

Assess Database Table – this is a standard extract from the assessor database containing about 25 elements including property valuation, site address, state use code, owner, owner address, and a selection of information about the structure. This table includes the FY (fiscal year) field, which stores the vintage of the assessed value of the parcel. The Fiscal Year Status Map pdf format of    Map of Fiscal Year of Assessed Level 3 Parcels  file size 1MB displays this information.

LUT Look Up Table – this is a look-up table for the MISC_TYPE attribute of the Misc feature class and the LEGAL_TYPE attribute of the OthLeg feature class.

UC_LUT Look Up Table – this is a look-up table for state use codes found in the assessing extract.

In ArcSDE, MassGIS stores the components of this data layer as follows:

    • TaxPar feature class: L3_TAXPAR_POLY
    • OthLeg feature class: L3_OTHLEG_POLY
    • Misc feature class: L3_MISC_POLY
    • The assessor data extract: L3_ASSESS
    • The two look-up tables are L3_LUT and L3_UC_LUT
    • A relationship class has been built to link the TaxPar feature class polygons to the assessing extract database table, named L3_TAXPAR_POLY_RC_ASSESS.
    • A spatial view was created that links the assessor records to the the TAXPAR polygons, named L3_TAXPAR_POLY_ASSESS.
 Complying with Level 3 of the Standard

Assessor’s parcel mapping is a representation of property boundaries, not an authoritative source.  The authoritative record of property boundaries is recorded at the registries of deeds and a legally authoritative map of property boundaries can only be produced by a professional land surveyor.

Representation of Parcel Boundaries - Users of parcel data, which MassGIS has approved as meeting the requirements for Level 3 of its standard, may find places where the boundaries conflict with visible features on orthoimagery.  This is common and reflects a variety of circumstances.  Often the discrepancy between the tax map and the visible road right-of-way on the orthoimagery base map is correct, as roads are not always constructed the way they were shown on the original plan.  Other factors accounting for discrepancies between the boundaries and visible features on the orthoimagery are buildings that may “lean” in the imagery because of camera angle, making them appear as if they are crossing parcel lot lines.  Also, while rights-of-way ordinarily have a standard width, that is not always true.  In fact, we have seen countless instances where right-of-way widths are irregular.  Similarly, the fence, wall, or shrub line visible on the orthoimagery is not necessarily the property boundary.  In some cases, houses are built so that they straddle lot lines.  Also, while MassGIS' quality assurance process is extensive and rigorous, it is not perfect and it is possible that we have missed some boundary compilation or other errors.

Municipal Boundaries - The standard requires that MassGIS’ representation of the official municipal boundaries be incorporated into the standardized assessor mapping.  Checking for that is part of our QA process.  However, there are discrepancies between municipalities where they share a boundary that follows a stream channel; without engaging the services of a surveyor, there is no way to determine where those boundaries are and we did not require that MassGIS’ mapping of that boundary supersede the boundary from the tax mapping. Also, MassGIS has allowed communities to represent the coastline as it is in their tax mapping.  Finally, this requirement from the standard uncovered numerous discrepancies in municipal boundary lines that will require further discussion with the communities involved.  Known outstanding boundary discrepancies include portions of the boundaries between the following communities: Andover-Lawrence, Lawrence-Methuen, Cohasset-Scituate, Attleboro-Rehoboth, Avon-Stoughton; Easton-Stoughton, and Dracut-Methuen.

Assessing Data Extract - The assessing data extract is an “as is” copy of the records maintained by each assessor. There are errors and discrepancies.

Assessing Data Match Rates - The standard sets very high requirements for the percentage of parcels that must match to an assessing record, as well as vice-versa. Full details are in the standard. However, these match rates were not always achievable.  In some communities, assessors do not know who owns some properties. These are almost always small fragments of land with no structure or small lots in wetland or forested areas.  The NO_MATCH attribute of the TaxPar feature class has been used to track these circumstances.  Although much less common, there are also occasionally records from the assessing extract beyond the allowed percentage that do not match to a parcel polygon.

Production

For each community, vendors delivered an ESRI file geodatabase to MassGIS. MassGIS staff reviewed the parcel boundary mapping, identifying potential errors.  Situations that were commonly called out in the boundary QA included lot lines running through structures, inconsistent right-of-way widths (unless the mapping was known to have been compiled from deeds and plans), discrepancies compared to visible features on the orthoimagery, and discrepancies relative to the official representation of the municipal boundaries maintained by MassGIS. Additional checks include: attribute names and domain values, consistency between “TAX” and “FEE” polygons included in the TaxPar and OthLeg feature classes, linking percentages from the parcel map polygons to the assessing data extract and vice versa, and review of situations where multiple tax records link to a single parcel and one or more of the tax records is not a condominium.

Attributes

Complete descriptions of the attributes for the Level 3 feature classes, database table, and the look-up tables are found in the parcel standard. Attribute table fields and domains (valid values) and selected definitions are listed here:

Field NameTypeSizeDec. PlacesValid ValuesNullRequired
Tax Parcel Attributes
MAP_PAR_IDC26 Parcel ID appearing on the original assessor's map YES
LOC_IDC18 M_<X>_<Y>(for meters), F_<X>_<Y> (for US Survey Feet) YES
POLY_TYPEC15 FEE, TAX, ROW, WATER, PRIV_ROW, RAIL_ROW YES
MAP_NOC4 Assessor's original map sheet number  
SOURCEC15 ASSESS, SUBDIV, ROAD_LAYOUT, ANR, OTHERNOYES(1)
PLAN_IDC40 Identifying information for plan used to update the digital file YES(1)
LAST_EDITN8 Format YYYYMMDDNO 
BND_CHKC2 null value, CC, NR, OK  
NO_MATCHC1 Y, NNO 
TOWN_IDN3 MassGIS town identifier (1-351)NOYES
 
Other Legal Interests Attributes
MAP_PAR_IDC26 Parcel ID appearing on the original assessor's map YES
LEGAL_TYPEC15 FEE, PRIV_ROW, RAIL_OVER, RAIL_ROW, ROW_OVER, EASE, CR, APR, CRX, APRX, OTHER YES
LS_BOOKC16  Registry of Deeds book for last sale YES(1)
LS_PAGEC14  Registry of  Deeds page for last sale YES(1)
REG_IDC15 The equivalent to Registry of Deeds book and page information but for registered or probate land. YES(2)
TOWN_IDN3 MassGIS town identifier (1-351)NOYES
TAXPAR_IDC18    
 
Miscellaneous Features Attributes
MISC_TYPEC15 WETLAND, ISLAND, TRAFFIC_ISLAND, WATER, OUTSIDE, BLDG YES
TOWN_IDN3 MassGIS town identifier (1-351)NOYES
 
Extract from Assessor
PROP_IDC30 Unlike the items below, this attribute may not come directly from the assessor’s database.  It may sometimes be constructed from information typically found in multiple columns in the assessor’s database (see definition for more information).  It must be unique within the city or townNOYES
LOC_IDC18 M_<X>_<Y> (meters), F_<X>_<Y> (US Survey Feet); use to join to parcel polygonsNOYES
BLDG_VALN9 Current assessed value for the main building(s) on the property YES
LAND_VALN9 Current assessed value for land YES
OTHER_VALN9 Other structures or physical improvements that are separately valued YES
TOTAL_VALN9 Current total assessed value for land and structures. Because some databases include other categories of valuation not included above, this may not represent the total of the fields above YES
FYN4 Fiscal year of assessed value formatted as YYYY (number, 4; cannot be null). See the Fiscal Year Status Map pdf format of    Map of Fiscal Year of Assessed Level 3 Parcels  file size 1MB based on this attribute.NOYES
LOT_SIZEN112Deed area in EITHER square feet OR acres, but not both YES
LS_DATEC8 Last sale date formatted as YYYYMMDD YES
LS_PRICEN9 Last sale price YES
USE_CODEC4 Land use code as set by Dept. of RevenueNOYES
SITE_ADDRC80 This field will contain the complete original site address as listed in the tax record YES
ADDR_NUMC12 This field will contain address number information, either a single house number with suffix (e.g., 25, 103 ½ or 12A) or a range of numbers (e.g., 12-16 or 12A–12B). YES(2)
FULL_STRC60 This field will contain the full street name, which may be stored in separate fields in the assessor database.  YES(2)
LOCATIONC60 This is the place to put secondary location information.   Frequently, descriptors such as “Side”, “South Side”, “Rear”, “Basement” as well as building and unit descriptors such as “#1” or “Unit A” are found in assessor data  YES(2)
CITYC25 City or town where the property is located YES
ZIPC10 Zip code where the property is located, if available  YES
OWNER1C80 Name of first owner of record YES
OWN_ADDRC80 The complete owner mailing address, including the street number, name, etc.  Where the tax bill is sent. YES
OWN_CITYC25 The city for the property owner’s address YES
OWN_STATEC2 For US addresses, the state where the property owner lives, using the postal service abbreviations for state YES(3)
OWN_ZIPC10 The zip code of the owner’s address  YES
OWN_COC30 The country where the owner lives YES
LS_BOOKC16 Last sale Registry of Deeds book  YES(1)
LS_PAGEC14 Last sale Registry of Deeds page YES(1)
REG_IDC15 This is the equivalent to Registry of Deeds book and page information but for registered or probate land  YES(2)
ZONINGC8 This is the code to indicate the zoning district within which the property lies not including overlay zoning districts  YES
YEAR_BUILTN4 format YYYY YES
BLD_AREAN9 Applies primarily to apartment buildings and commercial/industrial properties; assessor’s data is based on exterior building measurements.  Building area may be recorded as gross square-feet, adjusted gross square-feet, or finished area. Basement area may or may not be included in finished area.  Partial story-heights and attic areas may be treated differently by different CAMA systems.  Gross area may include non-living areas such as porches and decks, or attached garages. YES(2)
UNITSN4 Either living units; single-family=1, three-family=3 or number of residential or commercial condominium units within a GIS parcel.  YES(2)
RES_AREAN7 Applies primarily to 1, 2 & 3 family dwellings based on exterior building measurements or residential condominiums based on deeded unit areas.  Building area may be recorded as gross square-feet, adjusted gross square-feet, or finished area.  Basement area may or may not be included in finished area.  Partial story-heights and attic areas may be treated differently by different CAMA systems.  Gross area may include non-living areas such as porches and decks or attached garages.  YES(2)
STYLEC20 Code indicating style of structure (“colonial”, “ranch” etc.) YES
STORIESC6 This is not the wall height.  Story height is typically recorded as a full story for each floor, except under roof-line floors, which are adjusted by factors ranging from 10% to 90% of a full story depending on roof slope and wall height; examples include one-half stories and attics. Note that in the Patriot AssessPro database, letters (e.g. A, H) may be assigned to indicate partial story heights. YES
NUM_ROOMSN3  Total room count as determined by the assessor; primarily applied to residential properties. YES
LOT_UNITSC1 S (sq. ft.) or A (acres) (Added by vendor, not from assessor database) YES
TOWN_IDN3 MassGIS town identifier (1-351), added by MassGISNOYES
MA_PROP_IDC60 Unique identifier for ASSESS record, added by MassGISNOYES
 
(1) Only required if information is available
(2) Only required if information needed is available in the assessor's database
(3) Not required for owners with non-US addresses unless needed

Display and Download in OLIVER

To download data for a single municipality when viewing the Level 3 parcel data in OLIVER, add the "Political / Administrative Boundaries > Assessors Parcels > Parcels Level 3 FTP Download Links by Town" layer. When you identify on a town, you will see hyperlinks in the SHAPE_LINK and FGDB_LINK fields, for the shapefile and file geodatabase downloads, respectively. Click on the hyperlink to download a zipped file containing all the data for that municipality. Adding the "Parcel Status" layer will display the level of parcel data for each town. This permalink will bring up OLIVER with these layers added. Click on the image at right for an illustration (PDF). (Note: the zip files you may download in this manner are the same files downloadable from the Level 3 Parcels download page.)

Maintenance

These data are current to state fiscal years 2011 or 2012.  MassGIS will be vigorously encouraging communities to maintain their standardized digital assessor parcel mapping in compliance with Level 3 of the digital parcel standard.  From our discussions with companies that maintain assessor tax mapping for municipal clients, we know that maintaining Level 3 compliant data will be no more expensive than maintaining other forms of parcel mapping.  We also have discussed the standard with the Department of Revenue’s Bureau of Local Assessment and expect the Bureau will recommend that assessors maintain their mapping in compliance with Level 3 of the standard.

MassGIS has assembled information and resources for those interested in maintaining standardized parcel mapping.


Last Updated 10/30/2013