61 reference pages

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.

Horizontal and vertical datums, the ellipsoid and the geoid, NAD 83 and NAVD 88, and the modernized reference frames that replace them.

• What a datum isA datum is the agreed reference surface that turns a measurement into a coordinate. Surveying uses two kinds — horizontal and vertical — for two different reasons.
• Three surfacesGeodesy uses three surfaces — a mathematical ellipsoid, the gravity-defined geoid, and the physical ground. Confusing them causes most height errors.
• h = H + NThe single most useful equation in GNSS elevation work. What each term means, which sign convention applies, and where the error in the result comes from.
• GRS 80 and WGS 84GRS 80 and WGS 84 share a semi-major axis and differ in flattening only in the ninth digit. The practical difference is a tenth of a millimeter.
• NAD 27 vs NAD 83The shift from NAD 27 to NAD 83 changed the ellipsoid, the origin and the adjustment. Coordinates moved by tens of meters, by differing amounts.
• Realizations and epochsNAD 83 (2011) is not the same as NAD 83 (1986). A datum has versions because the network is readjusted and the ground itself moves — hence realizations and epochs.
• NGVD 29 and NAVD 88Two national vertical datums built on different principles. The difference varies across the country from roughly −0.4 m to +1.5 m, so no single conversion exists.
• NSRS modernizationNAD 83 is being replaced by NATRF2022 and NAVD 88 by a gravity-based geopotential datum. What is changing, why, and what a surveyor should do now.
• Geoid modelsA geoid model is a grid of geoid heights that turns GNSS ellipsoid heights into elevations. Hybrid and gravimetric models are not interchangeable.
• Height systemsLevel surfaces are not parallel, so a levelling loop does not close on raw height differences. Orthometric, dynamic and normal heights each answer that.
• CORS and OPUSBehind every published coordinate is a chain of observation, processing and adjustment. CORS and OPUS tell you how far to trust the number you hold.
• Datum transformationsThree tools for three problems — horizontal datum change, vertical datum change, and motion through time. Using the wrong one produces confident nonsense.
• Reading a datasheetAn NGS datasheet packs the provenance, accuracy and history of a control mark into a dense text format. Here is how to read it and what to distrust.

State Plane, UTM, low-distortion projections, and the grid-versus-ground arithmetic that decides whether a measured distance matches a published one.

• Why projections existYou cannot flatten a curved surface without distorting it. Every projection chooses what to preserve and what to sacrifice — surveyors pay in distance.
• State Plane zonesState Plane exists so surveyors can use plane coordinates over a whole state. Zones exist because a projection can only stay accurate over a limited width.
• Lambert vs TM vs obliqueThree conformal projections cover the United States. A zone's shape decides which it uses, and that decides whether scale varies with latitude or easting.
• Grid scale factorThe ratio between a distance on the grid and the same distance on the ellipsoid. Where it comes from, how it varies across a zone, and how large it actually gets.
• Elevation and combined factorThe elevation factor reduces a measured distance from the terrain to the ellipsoid. Times the grid scale factor it gives the combined factor you actually apply.
• Ground vs gridMultiply to go from ground to grid, divide to go back. The direction of the correction is the most common error in State Plane work, and it is systematic.
• Survey foot vs international footTwo feet differ by exactly 2 parts per million. On a State Plane northing of 2 000 000 ft that is 4 ft of position error, and nothing in the data will look wrong.
• UTMSixty zones, each 6° wide, with a fixed central meridian scale factor of 0.9996. Uniform worldwide, and about ten times more distorted than State Plane.
• Low-distortion projectionsA projection designed so grid distance equals ground distance to a few parts per million over a project area — removing grid-to-ground arithmetic entirely.
• Convergence and the three northsThree different norths, and the angle between the first two is the convergence of meridians. Where it comes from, how large it gets, and the sign people reverse.
• Latitude and longitudeLatitude and longitude, the three notations they are written in, how far a second of arc really is, and the formatting slips that move a point across the planet.

What 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.

• Boundary surveysA boundary survey locates the corners and lines of a parcel on the ground. What the work involves, what it can settle, and what it cannot.
• ALTA/NSPS surveysAn ALTA/NSPS Land Title Survey is a boundary survey tied to a title commitment, built to a national standard for commercial transactions.
• Topographic surveysA topographic survey maps the shape of the ground and what sits on it. How to specify accuracy, contour interval, features and file format.
• Construction stakingHow design coordinates become marks in the ground: calculating from plans, offsets, cut sheets, curve layout and the checks that prevent expensive rework.
• As-built surveysAn as-built survey measures what was built rather than what was designed. What it captures, who requires it, and why the timing matters more than the accuracy.
• Control surveysControl is the framework every other survey hangs on. How horizontal and vertical networks are designed, observed, adjusted and checked.
• Route surveysRoads, pipelines, transmission lines and rail are surveyed along a centerline. How stationing, alignment geometry and right-of-way work fit together.
• Subdivision plattingDividing land creates new parcels that must survive for centuries. How a subdivision moves from concept to recorded plat, and what the plat must carry.
• Hydrographic surveysSurveying beneath water adds sound speed, motion and tides to every measurement. How depths are measured, corrected and reduced to a vertical datum.
• Photogrammetry and lidarRemote sensing produces enormous amounts of data quickly, and none of it is accurate without ground control. How these methods work and where each belongs.
• Surveying glossaryOver fifty surveying terms defined plainly, grouped by theme, with notes on where the everyday meaning and the technical meaning part company.

How the NCEES Fundamentals of Surveying exam is structured, what each subject area covers, and how to build a study plan around it.

• What the FS exam isThe FS exam is the first licensure examination in surveying, normally taken near graduation. What it tests, who sits it, and what passing gets you.
• Format and appointmentThe FS is computer-based at a test center, with a searchable on-screen reference and a permitted calculator. What that means for how you prepare.
• Subject areasThe FS spans mathematics, measurement theory, boundary principles, geodesy and geospatial topics. How to read the specification and allocate study time.
• Eight-week study planA concrete eight-week schedule for the FS exam, built around diagnosis, targeted study, timed practice and a deliberate taper before the appointment.
• Math prerequisitesTrigonometry, coordinate geometry, angle handling and basic statistics underpin most FS exam questions. A checklist of what fluency actually means.
• Pacing and guessingMost FS candidates lose marks to the clock rather than to ignorance. A pacing method, a flagging discipline, and the arithmetic of guessing.
• Common mistakesUnits, the wrong foot, degrees versus radians, PT = PC + L, and the sign of a latitude. The recurring errors that turn understood problems into wrong answers.
• Exam dayTest center procedure, identification, permitted items and the shape of the day. Removing the logistical surprises so you can spend attention on questions.
• After the FSPassing the FS is the first of four stages. How experience is typically accumulated and documented, and how the professional exam differs, in general terms.
• Free resourcesFederal manuals, geodetic publications, state DOT survey manuals and USGS material are free and substantial. What each covers and where it falls short.