Sunday, March 22, 2015

PLSS CadNSDI – PLSS First Division (Sections)

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

The PLSS First Division is most commonly the Section.  Almost all PLSS CadNSDI users will have sections for the first division and this is also the most commonly known name for these components of the PLSS CadNSDI.  For simplicity many implementations will name the first division Section, and that is perfectly compliant with the standard.  The feature classes can have whatever alias works well in any jurisdiction. 

But it is important to realize that not all townships are divided into sections and it is sometimes important to be able to recognize the variations and to identify these divisions correctly in land descriptions or in data use.

First divisions do NOT overlap and all of the first divisions in a Township should completely cover or completely account for all of the area in a PLSS Township, except meandered water areas.

Typically sections are numbered in Boustrophedon order from 1 to 36, nominally defining one mile square areas. Boustrophedon meaning the numbers move across the township back and forth from east to west and then west to east much as oxen would plow the ground.  However, as with most things cadastral, there are many exceptions.  Some of these being

·      Sections are not always numbered starting in the Northeast corner of the Township.
·      There can be more than 36 sections in a Township.
·      Section numbers may be duplicated in a Township.
·      Sections are rarely one mile by one mile in size.

A typical PLSS Township with normal section divisions is shown below

Typical PLSS Township and Section Division

The attributes in the standard for the PLSS First Division are listed in the table below.  And as with the other feature classes in the standard the field lengths and aliases are locally configurable.  Additional fields or attributes can be appended to the feature classes.

This is the unique identifier for the PLSS Township in which the first division is located. Concatenation of the principal meridian, township, range, and duplication code that form a unique identifier for the township.
Township Identifier
This is a unique identifier for the first division that is built by appending the first division elements on the Township identifier.
First Division Identifier
This is the type of first division and is commonly the section but may be a lot, parcel, tract or other division.
First Division Type Code
This is the first division type as a text field
First Division Type Text
This is the number, letter or designator for the first division of the PLSS Township
First Division Number
This is a code to indicate whether the first division is a duplicated area or identifier
First Division Duplicate
This is the label for the first division that is used for cartographic of web display purposes
First Division Label
Code for the type of special survey typically from the codes for the BLM data collection.  Used in this feature to indicate if the feature is unsurveyed or protracted.
Survey Type Code
The description of the survey type code. 
Survey Type Text
The date of the source document
Source Doc Date
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

The domains for the First Division Type are shown below.  In an implementation the type description is typically more important than the code.  Both the code and description are provided because we have found the codes alone can be a bit confusing for most users.  The codes are used in the Identifiers but it is compliant with the standard to list the type description only. 

First Division Type Code
First Division Type Description
Unsectionalized Area
Unsectionalized areas are lands that were never divided and no protraction or definition of division was generated.  Over time these areas are expected to have division types added
The section is the most commonly occurring first division and is nominally one mile on a side.  The section numbers are commonly 1 to 36 but section numbers as high as 48 have been identified.
These are lots that occur only rarely in non-sectionalized Townships.  In these cases the township is divided into lots, but again this is a rare occurrence. 
Protracted Block
Protracted Blocks are divisions that provide a defined division in unsurveyed PLSS Townships.  Protracted Blocks are defined by the coordinate values of the corners. These map also have been or be called protraction blocks.
FS **
Fractional Section
Fractional sections are sections that are invaded by water or a protraction such that at least one quarter corner cannot be established and the method for subdividing the section is modified.  The fractional sections may not have been identified in some of the early standard implementations.
Quarter Township
The quarter townships exist in Ohio only.  These are divisions that quarter the township and in some cases the quarter township is quartered again into four lots or parcels.
There are two uses of Tracts as a first division. (1) PLSS Tracts in the eastern states that should be in the PLSS Special Survey Feature Class but are included in the First Division as a transition to the fully compliant standard. (2) Paragraph 3-122 of the 1973 manual and 3-199 in the 2009 manual
 "when administration or disposal requires no subdivision, an island is given a tract number within a township.  In such cases, the section lines need not be extended to the island."  
UP *
Unsurveyed Protracted
Unsurveyed Protracted divisions are always a section but have not been measured by survey. The protraction diagram is a plan of survey.
UN *
Unsurveyed Unprotracted
Unsurveyed Unprotracted divisions are always sections but there is no survey or plan of survey.  These divisions have been termed extended PLSS or PLSS grids in some implementations.
If the type of first division is not known than this code and description is available as a placeholder until the type of first division can be established.
* The Unsurveyed Protracted and Unsurveyed Unprotracted values reference the survey status or survey condition of a Section.  The first division type for features coded as UP or UN is Section (SN). The Survey type code and description in the PLSS CadNSDI feature classes should be used to indicate the survey status of the feature.  These domains are included as transitional values and will be eliminated over time.
** The fractional section is a legitimate first division type, but thus far all fractional section sections have been identified as sections. 

Some of the more frequently occurring First Division types that are not sections are shown Lots, Protracted (or Protraction) Blocks, and Quarter Townships.  Examples of each are shown below.

Protracted Bocks in Utah (Protraction Blocks)

First Division Lots in Wisconsin

Quarter Townships in Ohio

There are many other anomalies and exceptions throughout the PLSS.  Things like duplicated section numbers, sections with numbers greater than 36 and many other unusual configurations.  If there is an unusually situation or configuration, ask the identified data steward for clarification.

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