The NPRC parcel datalayer contains property (land lot) boundaries and select attributes about each property. NRPC compiled this information over many years from various sources including original tax maps that were subsequently georeferenced and digitized by the Commission. As such, the data is suitable for tax assessment purposes but is not survey-quality.

The datalayer contains discrete, non-overlapping polygons. Non-contiguous lot areas are modelled as multi-part polygons. Public rights-of-way and water bodies are stored as non-numbered lots to void the creation of null voids in the parcel fabric. Parcels are edge-matched along town borders. Along the MA state border parcels conform to the Towns from Survey Points datalayer available from MassGIS; in most other cases the parcels are matched to the 1:24K town border datalayer (pba) derived from USGS topo maps and available from NH Granit. In cases where GIS parcel information did not conform to the USGS town boundary linework, NRPC interpreted tax map geography and dimensions and mapped parcel boundaries accordingly.

Over time, NRPC has maintained this database by monitoring the Hillsborough County Registry of Deeds online database for recordings related to subdivisions, lot mergers, and lot line revisions. NRPC has maintained a very high match rate between the parcel database and corresponding assessing records. The cardinality between parcels and assessing records is 1:M. In some cases, the NRPC edit may precede the corresponding update on the municipal property record card. For this reason, some parcels may not yet have a matching assessing record, or the parcel attributes may not be exactly consistent with the assessing record.

Disclaimer: These data are an NRPC interpretation of original source maps and are appropriate for planning purposes; they should not be utilized where legal and surveyed property boundaries are required. The most current property information is on file within each respective City or Town. Edges between towns in this dataset are not authoritative delineations of town boundaries. NRPC and its member communities, respectively, do not make any warranty, representation, or guarantee as to the content, sequence, accuracy, timeliness, or completeness of any of the information provide herein. The user should not rely on the data provided herein without verifying its accuracy independently. NRPC and its member communities, respectively, explicitly disclaim any representations and warranties including, without limitation, the implied warranties of merchantability and fitness for a particular purpose. NRPC and its member communities, respectively, shall assume no liability for any errors, omissions, or inaccuracies in the information provided regardless of how caused and for any decision made or action taken or not taken by the user in reliance upon any information or data furnished hereunder.