The development of this data layer was initiated in the early 1990's as
a collaboration between the Society for the Protection of NH Forests (SPNHF),
the NH Office of Strategic Initiatives (OSI), and the Earth Systems Research
Center at the University of New Hampshire (ESRC). While the methodologies
used to develop the data set have evolved over a period of years, the
basic approach has remained relatively constant throughout this period.
As of 2001/2002, the entities responsible for the development of the data
set include: OSI (collection, compilation, and automation of state/federal
lands), the regional planning agencies (collection, compilation, and automation
of municipally-managed parcels), SPNHF (collection and compilation of
Forest Society Lands), and ESRC (collection, compilation, and automation
of all other protected lands, and integration of all contributions into
a seamless, statewide data set).
The process starts with the collection of source information (PARCELSOURCE)
from agencies protecting/managing parcels in the state. Protecting agencies
typically include state/federal organizations, county/municipal agencies,
land trusts, watershed associations, and other non-profit organizations.
The protecting entity is asked to provide the best available source map,
and the associated descriptive information, to the organization responsible
for parcel compilation (SPNHF, OSI, an RPA, and/or ESRC).
The organization recompiling the tract/parcel information must typically
re-scale the source maps to achieve the target compilation scale of 1:24,000.
This is accomplished via traditional copying machines with variable reduction
capabilities. (For data that is digitally transmitted (e.g. DXF/DWG files),
this step is omitted.) Once the source parcel is scaled appropriately, the
parcel boundaries are recompiled onto 7.5-minute quad-based mylars. Prior to
the late 1990's, these mylars displayed DLG-3 source data and any existing
parcels in the data base. More recently, the DOTROADS data have replaced
the DLG-3 roads.
During recompilation, tract/parcel boundaries that are coincident with any
base features are flagged appropriately. Color codes are used to
indicate whether the intended coincidence is with a base map road,
surface water feature, town boundary, etc.
When new parcels are mapped that share boundaries with existing
tracts/parcels, the compiler must select the best boundary to
utilize. In these instances, attribute data (e.g. SOURCE, ACCURACY, etc.)
associated with the existing and the new parcel are reviewed, and a
determination is made.
The recompiled boundaries are then digitized, using standard GRANIT
automation tolerances. This automation may take place at several
locations (as noted above). During the digitizing phase, all flagged,
coincident boundaries are replaced with the appropriate base feature
from the GRANIT database. This ensures consistency of the resulting
tracts/parcels with the GRANIT base layers. Boundary arcs and polygons
are then coded. If the automation is handled by OSI or a regional
planning agency, the new parcels are submitted to GRANIT for final
review and incorporation in the statewide layer.
Checkplots are generated as each quad is updated, to ensure the accuracy
of the linework digitizing and arc/polygon coding. Attributes are entered
and verified through visual checks and by processing against valid domains.
Note that certain attributes have been added since the original template was
defined. As a result, not all fields will be populated for all records.
As part of the June, 2017 update, a large number of boundary updates were made to
the White Mountain National Forest (WMNF) utilizing data provided by The Nature
Conservancy. In addition to edits made to the WMNF itself, the updates yielded
many changes to the boundaries of adjacent parcels.
In Spring, 2019, NH GRANIT partnered with UNH Cooperative Extension to capture
property ownership information. A new field (OWNERTYPE) was added to the
database to report on the type of land ownership (e.g. state, federal, private, etc.),
similar to the PPAGENTYPE field which speaks to type of protection. The primary source
used to obtain ownership information was the NH parcel mosaic dataset (NH
Department of Revenue Administration, February, 2019). If ownership information
could not be obtained using the parcel mosaic, ownership codes were assigned if
sufficient protection coding existed to make an informed decision. If still no
determination could be made, the communities in which these lands were located
were contacted to clarify ownership status.
Further information on the derivation of the data set and the standards
utilized may be obtained from the GRANIT database manager at ESRC.
