FS Surveying common mistakes
FS Surveying · Understand the traps and how to avoid them.
Computes a horizontal distance or coordinate inverse directly from State Plane coordinates and reports it as the ground distance, never applying elevation or scale factors.
Grid coordinates look like ordinary plane coordinates, and the problem may hand you the zone scale factor and average elevation in a separate sentence that is easy to treat as background information.
What to do instead
Before any inverse, write 'grid' or 'ground' next to the number. Convert with combined factor CF = EF x SF, where EF = R/(R + h); carry the combined factor to at least six decimals and state the result's basis in the answer.
Runs a traverse adjustment by distributing the linear misclosure to latitudes and departures first, using bearings computed from unadjusted angles, and only afterwards spreads the angular misclosure.
Adjustment is learned as a checklist, and the angular step feels like a formality that can be tacked on at the end of the computation sheet.
What to do instead
Fix the order: (1) angular misclosure, (2) distribute it and recompute each azimuth, (3) compute latitudes and departures from adjusted azimuths, (4) linear misclosure, (5) apply the compass rule to lat/dep, (6) recompute coordinates and verify closure is zero.
Finds a monument that does not match the record distance and resolves the conflict by holding the deed distance and calling the monument 'off' or 'not the original'.
Record numbers feel authoritative and precise, while an old pipe or stone looks crude, so the candidate defers to the number.
What to do instead
Apply the hierarchy of evidence: natural monuments, then artificial monuments, then courses and distances, then area. Monuments control; distances yield. Use the record distance only as corroboration of the monument's identity, and state the reasoning explicitly.
Substitutes percent grades directly into vertical curve equations as if they were decimals (uses g = 3 instead of 0.03), producing elevations that are wrong by a factor of 100.
Exam statements give grades in percent while formula sheets and textbooks show g as a slope, and the unit is never written down during the calculation.
What to do instead
Convert every grade to a decimal at the moment you extract it from the problem and write the conversion on the page. Sanity-check by computing the elevation change over the full curve (g2 - g1)xL/2) and confirming it matches the PVI elevations within a few hundredths.
Inverts the photogrammetric scale relationship, dividing flying height above terrain by focal length when asked for the scale denominator, or multiplying when it should divide.
The relation S = f/H is simple, but the '1:S' convention and the need to use height above mean terrain rather than above datum invite a flip.
What to do instead
Write S = f/H with both terms in the same units to get a dimensionless ratio, then invert for 1:S. Check the direction: increasing flying height must make the scale smaller (larger denominator); a result that violates that check is wrong.
Reduces total station distances without confirming the prism constant and EDM offset in the instrument, or applies a -30 mm constant to a prism that is actually 0 mm.
Instruments ship with a default constant and the setting persists between jobs, and in the field the discrepancy is small enough to be absorbed by other errors.
What to do instead
Treat prism constant as a recorded observation: check and log the instrument setting against the prism label before the session, and verify with a known baseline or a check shot between two coordinated points. In exam items, state the constant you assumed.
Computes slope-stake catch-point offsets in a single pass using the cut or fill depth measured at the centerline, without accounting for the different depth at the actual catch point.
The centerline depth is the only elevation shown on the cross-section, and the one-step formula looks complete.
What to do instead
Recognize that cut/fill varies with offset: solve iteratively or algebraically for the offset d where the ground elevation equals the design elevation at that same offset, adding the half-width of the traveled way and shoulders first, then converging once or twice and rounding to the nearest 0.1 ft.
Computes a parcel area by the coordinate method from a list of corner coordinates without verifying that the traverse closes, then reports the raw algebraic sum of cross products as the area.
The shoelace routine is quick to apply mechanically, and the sign convention and the division by two are easy to drop under time pressure.
What to do instead
Close the coordinate list by repeating the first point, sum the cross products, take the absolute value, and divide by two; verify with an independent rough rectangle estimate and check that units are square feet before converting to acres by dividing by 43,560.
Answers professional-practice items by assuming a limitation-of-liability clause or a client's waiver removes the surveyor's duty to exercise reasonable care toward the public and third parties.
Candidates reason from the commercial relationship (the client pays) rather than from the statutory public-protection standard, and contract language sounds absolute.
What to do instead
Separate the two issues: a contract clause may allocate or cap risk between contracting parties, but it does not lower the standard of care or extinguish duties owed to the public, adjoining owners, and third parties who reasonably rely on the work.
Starts computing a boundary from the deed calls immediately, skipping the chain-of-title and adjoiner research and the field reconnaissance of found monument evidence.
Computation feels like progress and the research step produces no numbers, so it gets compressed or deferred until the computations disagree.
What to do instead
Do the research and reconnaissance first and document it: pull the subject and adjoiner deeds and plats, list every record and found monument with its position and condition, and only then begin the boundary resolution, using research to explain discrepancies rather than to patch them afterwards.