PLSS CadNSDI – PLSS Townships

This is the fourth of a series of documents that describe the contents of the PLSS CadNSDI data set.

The PLSS Townships are the primary unit of survey for the PLSS, nominally six miles on a side, usually containing 36 sections. PLSS Townships are numbered from base lines and principal meridians. This feature class provides the polygons for the PLSS Townships. The diagram below illustrates the basic PLSS Township referencing and numbering.

(from http://geology.isu.edu/geostac/Field_Exercise/topomaps/plss.htm last accessed March 2015)

A fairly typical set of Townships with their sections is shown below.  The Townships are designated with the Township (Tier) number and direction and the range number and direction.  For example the Township in the middle is Township 30 North Range 31 East.

But to be complete the Townships also need a principal meridian reference.  The list of Principal Meridians (PM) and their national two digit codes are listed at the end of this article.  A map illustrating the principal meridians can be found at this link

http://www.blm.gov/style/medialib/blm/wo/MINERALS__REALTY__AND_RESOURCE_PROTECTION_/lands_and_realty.Par.1381.File.dat/meridianmap09.jpg

A detailed text describing the history and development of each principal meridian and baseline (Initial Points) can be found at this page (Click on Al White for a link to the book).

http://www.pmproject.org/index.htm

The attributes for the PLSS Township are listed in the following table.  The field lengths for the attributes may be adjusted in some implementations; this is compliant with the standard intent.  The field names and intended content are the focus of the implementation standard.

PLSS Township Attributes

FieldName	Type	Length	Description	AliasName
STATEABBR	String	2	State abbreviation code two letter postal code	State Abbreviation
PRINMERCD	String	2	Principal meridian code from the BLM PM Code list	Principal Meridian Code
PRINMER	String	40	Principal meridian name as a text	Principal Meridian Text
TWNSHPNO	String	3	Township number. The Township Number indicates the number of rows of townships, north or south from a Public Land Survey System Origin.	Township Number
TWNSHPFRAC	String	1	Township fraction. Township Fractions are created when there are gaps between surveyed Township boundaries or due to excess size in Townships that arose from executing original surveys.	Township Fraction
TWNSHPDIR	String	1	Township direction. The direction of a row of Townships from a Public Land Survey System Origin. These are typically North and South in the West but may be East and West in Ohio	Township Direction
RANGENO	String	3	Range number. The Range Number indicates the number of columns of townships, east or west from a Public Land Survey System Origin.	Range Number
RANGEFRAC	String	1	Range fraction. Range Fractions are created when there are gaps between surveyed Township boundaries or due to excess size in Townships that arose from executing original surveys.	Range Fraction
RANGEDIR	String	1	Range direction. The direction of a column of townships from a Public Land Survey System Origin. These are typically East or West in the west but may be north or south in Ohio	Range Direction
TWNSHPDPCD	String	1	If there are multiple townships in a Public Land Survey System Origin, State and Survey Name, the Township Duplicate Status is used to establish uniqueness. When more than one Public Land Survey System Township has the same Township and Range numbers and directions and fractions, and is in the same State, this attribute is used to distinguish among duplicate values.  A is the first duplicate, B the second etc.  A 0 in this field indicates no duplicates	Township Duplicate
PLSSID	String	50	Concatenation of the principal meridian, township, range, and duplication code that form a unique id.	Township Identifier
TWNSHPLAB	String	20	Township label that is used for cartographic output or web display	Township Label
SRVNAME	String	60	A common or otherwise recognized name for a portion of area of a PLSS Survey, for example the refugee lands in Ohio or in cases where a PLSS Township has a recognized name.	Survey Name for PLSS Areas
SURVTYP	String	2	Code of the type of special survey, typically these are the codes described in the BLM data collection as survey type codes	Survey Type Code
SURVTYPTXT	String	50	Special survey type text description, for interpreting the codes	Survey Type Text
SOURCEDATE	Date	8	The date of the source document	Source Date
SOURCEREF	String	100	The reference to the source document could be a reference to a map or plat or a deed. This could include document type.	Source Doc Link or Reference

Why is the state included in the PLSS Township Table?  This is because in some cases, notably along the Colorado-Kansas boundary, the Principal Meridian, numbers and directions for two “columns” of townships are repeated, with the only unique designation being the state.  Also many state boundaries in the west are coincident with Township boundaries.  Townships that are split by state lines are divided into two polygons for the standardized data.

The survey type is used to identify unsurveyed townships and townships that have been defined on a protraction diagram, which is a plan of survey.  If the survey type is blank, the township boundary has been surveyed.  The source date and source reference are optional fields that can be used to identify the first date of survey and the source document, typically a General Land Office (GLO) or BLM plat.

The figure below illustrates some fractional or half township and half ranges in Nevada. Fractional parts can be half, quarter, or three quarters.  Fractional townships may not be familiar to many of the PLSS data users, but they occur in almost every state.

The other exceptional coding are the duplicate townships.  This happens when the Township tier, range, and PM are duplicated within a state.

The image below is from a portion of the Ohio PLSS from the Ohio River Base PM.  The Township labels have the duplicate code at the end.  The first duplicate has an A indicating that another Township with the same designation exists.  The convention is to assign the first duplicate code, A, to the township closest to the baseline or PM.

The Principal Meridians included in the PLSS CadNSDI standardized data are listed.

Principal Meridians

Principal Meridian Code	Principal Meridian Description
01	1st Meridian
02	2nd Meridian
03	3rd Meridian
04	4th Meridian
05	5th Meridian
06	6th Meridian
07	Black Hills Meridian
08	Boise Meridian
09	Chickasaw Meridian
10	Choctaw Meridian
11	Cimarron Meridian
12	Copper River Meridian
13	Fairbanks Meridian
14	Gila-Salt River Meridian
15	Humboldt Meridian
16	Huntsville Meridian
17	Indian Meridian
18	Louisiana Meridian
19	Michigan Meridian
20	Montana Meridian
21	Mount Diablo Meridian
22	Navajo Meridian
23	New Mexico Meridian
24	St. Helena Meridian
25	St. Stephens Meridian
26	Salt Lake Meridian
27	San Bernardino Meridian
28	Seward Meridian
29	Tallahassee Meridian
30	Uintah Meridian
31	Ute Meridian
32	Washington Meridian
33	Willamette Meridian
34	Wind River Meridian
36	Between the Miamis
37	Muskingum River
38	Ohio River Base
44	Kateel River Meridian
45	Umiat Meridian
46	Extended Fourth Meridian
47	West of the Great Miami
48	Base Line of the US Military Survey
99	Not Applicable

PLSS CadNSDI – PLSS and CadNSDI Basics

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

http://nationalcad.org/download/PublicationHandbookOct2014.pdf

http://nationalmap.gov/small_scale/a_plss.html

http://www.blm.gov/wo/st/en/prog/more/cadastralsurvey.html

http://proceedings.esri.com/library/userconf/proc03/p0414.pdf