Reference · 16 pages
Public Land Survey System
Townships, ranges, sections and aliquot parts as the BLM Manual of Surveying Instructions describes them — how the rectangular system was laid out, how corners were monumented, and how a retracement follows it.
- What the PLSS isThe PLSS is the rectangular survey that turned the American public domain into saleable parcels. Here is what it is, why it exists, and which states use it.
- Principal meridiansEvery PLSS survey begins at an initial point where a principal meridian meets a base line. How those lines were run, and why each system stands alone.
- Townships and rangesHow T3N, R2W, of the 6th Principal Meridian works: what a township and a range are, how they are counted, and what a normal township contains.
- Correction linesMeridians converge toward the pole, so a rectangular survey cannot tile the earth. Standard parallels and guide meridians restart the grid every 24 miles.
- Section numberingA township holds 36 sections numbered in a serpentine: 1 in the northeast, west to 6, then back east 7 to 12, ending at 36 in the southeast corner.
- Aliquot partsHow to read a PLSS aliquot description right to left, what each part contains in acres and chains, and which descriptions are not aliquot at all.
- Government lotsGovernment lots cover parts of a section that will not divide into quarter-quarters. What creates them, how they are numbered, and where the acreage comes from.
- Excess and deficiencyThe PLSS decides in advance where its measurement error will land. All excess and deficiency is placed in the north and west half-miles of a township.
- Types of cornersThe PLSS uses several kinds of corner, each with a different job. Confusing a closing corner with a standard corner will move an entire township.
- Monuments and accessoriesWhat the original surveyors actually set at a PLSS corner, how they marked it, and how accessories such as bearing trees let a lost-looking corner be recovered.
- Original versus retracementIn PLSS country the original survey is unimpeachable once title has passed. Retracement means finding what the original surveyor did, not improving on it.
- Lost or obliteratedAn obliterated corner has lost its monument but not its position. A lost corner has lost both. Which one you have determines whether you search or proportion.
- Single proportionSingle proportionate measurement restores a lost corner along one line, distributing the record-to-measured difference in proportion to the record distances.
- Double proportionDouble proportion restores a lost interior section or township corner from control in four directions, intersecting a north-south and an east-west proportion.
- Meander linesA meander line was run to compute area, not to fix a boundary. Where a PLSS parcel fronts meandered water, the water itself is generally the boundary.
- Subdividing a sectionThe original survey monumented only the section and quarter corners. The center of section and the quarter-quarter corners are established later, by rule.
Other sections
All reference- Datums & heightsHorizontal and vertical datums, the ellipsoid and the geoid, NAD 83 and NAVD 88, and the modernized reference frames that replace them.
- Coordinate systems & projectionsState Plane, UTM, low-distortion projections, and the grid-versus-ground arithmetic that decides whether a measured distance matches a published one.
- Survey types & practiceWhat an ALTA/NSPS survey is and is not, boundary versus topographic versus construction work, and the vocabulary a client, an attorney and a field crew each use for the same thing.
- FS exam guideHow the NCEES Fundamentals of Surveying exam is structured, what each subject area covers, and how to build a study plan around it.