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I am creating a GUI for input of PLSS data (Township, Range, Section). There will be 5 pull down or spinner components:
Township, North/South, Range, East/West, Section

The North/South component will have 2 selections: North, South
The East/West component will have 2 selections: East, West
The Section component will have numbers 1-36

What are the range of numbers for Township and Range?

This is the meridian of concern https://en.m.wikipedia.org/wiki/New_Mexico_meridian

PolyGeo
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Al Lelopath
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3 Answers3

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To start with, Sections in a PLSS Township range from 1 through 36, not 32. The number of Townships varies according to the Principal Meridian they are referenced to.

Rudy Stricklan
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To add what Rudy Stricklan states, the nominal township is a square, six miles on a side, containing 36 evenly-divided sections. However, townships and their subdivisions may deviate - both in number and in shape - for a variety of reasons, from the difficulties encountered while surveying through rugged terrain to fraudulent 1800's era survey reports compiled not in the field, but at the local watering hole (or so I've been told - I'm not a surveyor).

For example, in Washington State, half-townships were added to "fill in the gaps" between different initial survey projects that did not properly meet up. Additionally, there are other types of subdivisions in addition to sections (including donation land claims, federal tracts, and protracted blocks). To see this complexity first-hand, Washington state townships/section data can be downloaded here, and here's the metadata.

Perhaps your area of interest will not include any of the anomalies I've mentioned. On the other hand, you may want to account for all potentialities.

Stu Smith
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Building further off of Stu's answer: You can download PLSS data from BLM here. All the information you want is likely in those attribute tables. For the range of possible Township #'s, for example, select by attribute on the meridian you are interested in and then find all the unique values in the "PLSS Township Number" field. To account for those 'half townships' Stu mentions, look at the "PLSS Township Fraction" field. You could similarly find unique values for this field and add an additional GUI component for the fraction, or perhaps use the field calculator to concatenate the two fields before searching for unique values.

Looking at the tables for the Sections layers and Second Divisions Layer may help you figure out if you need to include options for some of the other types of subdivisions mentioned by Stu

Nick
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