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