This is the third of a series of
documents that describe the contents of the PLSS CadNSDI data set.
The Public Land Survey System (PLSS) was
first and foremost an inventory of public domain lands designed to determine
what the land assets and uses existed on the vast public holdings. The measures and divisions on the land were
used to parcel these holdings so they could be offered for sale or held for
national use. The public domain lands
(sometimes called PD lands and the 30 states where these lands exist are
sometimes called the PD states) are lands owned by the Federal government for
the benefit of the citizens of the United States. Within the PD lands are
non-PD lands such as land grants, tracts, and other lands that were occupied or
owned prior to U.S. acquisition or prior to PLSS survey. The original land inventory and surveys have
become the basis for legal land descriptions.
There are many technical considerations
and impacts to land rights that depend on when and how lands came into public
or private ownership. This document is
not that description. This document and
all of the documents in this series describe the PLSS CadNSDI polygons
(parcels) and the attributes and non-nominal configuration of these surveys and
polygons.
The PLSS may appear to be a relatively
simple system of hierarchical squares but in fact it is a very complex and
highly variable system. For every rule
there are a myriad of exceptions. For
example, the simple fact that all PLSS Townships are defined as being north or
south of a baseline is not even universally true as there are many PLSS
Townships that are referenced East and West.
One of the most common misconceptions
about the PLSS is that it covers all thirty states with a continuous and
uniform grid of six-mile squares that are then further divided into one-mile
squares. This couldn’t be further from reality.
The PLSS is NOT a mathematical
system; it is a legal land division that is defined by corners on the ground
that were established according to sets of instructions to surveyors that
evolved over time. The “rules of
engagement” for land surveyors establishing the PLSS changed as the PLSS
evolved. What was true in one area may
be different in another.
The PLSS is not all rectangular. There are important components of the PLSS
that are non-rectangular. The
rectangular PLSS is a simultaneous land description meaning that all of the
lands covered by a rectangular survey were described in one survey and all of
the lands within that described area of equal standing, meaning there are no
junior or senior rights among equal levels of division. The condition is commonly called a
simultaneous conveyance or simultaneous creation in the parlance of land
surveyors.
The elements of the rectangular PLSS are
described in Chapter 3 of the 2009 BLM Manual of Instructions (The BLM 2009
Manual of Instructions is not available in digital form but information on
ordering the Manual can be found at this link (http://www.blmsurveymanual.org/ (last accessed March 2015)). These are
surveys where the PLSS contains elements that are defined with the nested
hierarchy. An irregularly shaped PLSS
Township, fractional townships and half townships are all rectangular surveys.
Non-rectangular PLSS surveys are called
special surveys. They are described in
Chapter 10 of the BLM Manual of Instructions, 2009 edition. Special surveys are
created when it is necessary to protect an existing interest or pre-existing
condition, such as when particular rights or interests have been designated by
legislation and require a special surveying method or to separate federal
interests from private or other non-federal interests. In most cases the special surveys create
“holes” in the rectangular data. That
is, in areas where a special survey is created, the underlying rectangular
information is either no longer valid or never existed. There are exceptions, as there are with all
things cadastral.
General Rules for the Rectangular PLSS
·
The rectangular survey is a
simultaneous conveyance
·
The polygons are created as a
nested hierarchy
·
Surveys are not segregated
·
Lost corners within rectangular
surveys can be re-established by proportionate methods because of equal rights
among polygons
General Rules for Non-Rectangular PLSS or Special
Surveys
·
They protect an existing private
right
·
They carve out a new right
·
They may be measured by metes and
bounds and may have crossing closing corners
·
They have a junior/senior right
relationships for rights among themselves and with the rectangular PLSS
·
They may be segregated
Segregation is the process of defining
lots (sometimes called government lots) around a non-rectangular PLSS survey to
provide land descriptions for land that does not follow the regular quartering
and halving for aliquot parts but are still lands in the rectangular PLSS land
description system.
If the lands have never been in the
public domain (non-PD lands) the survey measurements and divisions are
described in the Survey System feature class.
Polygon Identification Codes
Every polygon in the standardized data has a
unique identifier or identification code.
These identifiers are “intelligent” in the sense that they are built
from the polygon type and location. The
Subcommittee recognized that a sequentially assigned non-intelligent identifier
is a preferred approach in database design references and texts, but given the
volume of existing data, the preferences of users, and the challenge in
building a nationwide systematically assigned non-intelligent identifier that
would be recognized by the multitude of data producers would be difficult and
costly to build and then effectively maintain.
Many states and local government have internal identifiers that can be
used to construct the national standard identification code.
There are
many online documents that provide extensive descriptions and discussions on
the PLSS and its many nuances. Some of
these include
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