DC Land Surveyor Exam common mistakes
DC Land Surveyor Exam · Understand the traps and how to avoid them.
When computing a boundary line from record bearing and distance, the candidate calculates the bearing using the arctangent of ΔE/ΔN without regard to the signs of ΔN and ΔE, producing a bearing in the wrong quadrant and misplacing the corner.
Most calculators and spreadsheets return arctangent values only between -90° and +90°, so candidates who do not manually inspect the signs of ΔN and ΔE default to the first or fourth quadrant. The error is easy to miss because the distance and the numerical angle are correct.
What to do instead
Always compute the bearing from the signs of ΔN and ΔE using a quadrant check: NE (ΔN>0, ΔE≥0), SE (ΔN<0, ΔE>0), SW (ΔN<0, ΔE<0), NW (ΔN>0, ΔE≤0). Use atan2(ΔE, ΔN) when available, and verify by back-computing the northing and easting from the final bearing and distance.
When reducing a total station traverse, the candidate applies a compass-rule or transit-rule adjustment to the raw field angles and distances before reducing them, or adjusts only the latitudes and departures but not the coordinates, so the adjusted traverse does not close on the starting coordinate.
Candidates memorize adjustment formulas but lose track of the sequence: angles must be balanced first, then bearings computed, then latitudes and departures, then coordinate adjustments. Applying corrections in the wrong order or omitting the final coordinate update produces a traverse that appears adjusted but still has a misclosure.
What to do instead
Follow a fixed reduction sequence: (1) balance interior angles to the geometric sum, (2) compute bearings from the balanced angles, (3) compute latitudes and departures, (4) compute linear misclosure and relative precision, (5) distribute latitude and departure corrections (compass rule: correction proportional to length), (6) apply corrections to coordinates and verify the adjusted traverse closes exactly. Check relative precision against the project standard before accepting.
When converting between State Plane, UTM, and ground coordinates, the candidate treats the grid scale factor and the elevation factor as a single combined factor or ignores one of them, so the ground-to-grid distance conversion is off by tens of parts per million.
The combined factor is the product of the grid scale factor and the elevation factor. Candidates often remember only the grid scale factor or only the elevation factor, and because the numerical difference is small (often less than 0.001), the error is not obvious in a single distance but accumulates in large projects.
What to do instead
Compute the combined factor explicitly: combined factor = grid scale factor × elevation factor, where elevation factor = R/(R+h) using the ellipsoid radius at the project latitude and the ellipsoid height. Apply the combined factor to ground distances to obtain grid distances, and divide by it to go from grid to ground. Verify with a known baseline or a check between two published control points.
When evaluating a boundary retracement, the candidate applies the priority-of-evidence rules in the wrong order, for example elevating a record distance over a monument called for in the deed, or treating a later survey as controlling over the original grant.
Candidates memorize a list of evidence types (monuments, courses, distances, area, coordinates) but do not internalize that the order is hierarchical and that natural monuments generally control over artificial monuments, which control over courses and distances. The error is compounded when the deed is ambiguous or when a later survey conflicts with the original.
What to do instead
Apply the hierarchy consistently: natural monuments > artificial monuments > courses and distances > area > coordinates. In a retracement, the original survey controls; later surveys are evidence of where the original line ran but do not change the boundary. When evidence conflicts, document each item and explain why the higher-ranked evidence controls. Practice with deeds that mix monuments and distances to reinforce the order.
When performing a least-squares adjustment, the candidate reports the a posteriori variance of unit weight and the standard deviations of the adjusted coordinates without checking the degrees of freedom, or accepts an adjustment with a failed chi-square test because the residuals look small.
Candidates focus on the arithmetic of the normal equations and overlook the statistical diagnostics. A small residual does not guarantee a valid adjustment; the reference variance must be consistent with the a priori variance, and the degrees of freedom must be positive and correctly counted.
What to do instead
After the adjustment, compute the a posteriori variance of unit weight, σ₀² = (VᵀPV)/(n−u), where n is the number of observations and u is the number of unknowns. Compare the square root to the a priori standard deviation and perform a chi-square test at the chosen confidence level. Report the degrees of freedom and flag any adjustment where the test fails. Check for blunders using standardized residuals before accepting the solution.
When classifying a water boundary or tidal boundary, the candidate applies the ordinary high water mark or the mean high water line without confirming which line the relevant state law or deed establishes, and without accounting for avulsion versus accretion.
Water boundary rules vary by jurisdiction and by the nature of the water body (tidal navigable, non-tidal navigable, non-navigable). Candidates often apply a single rule learned from one example and miss that avulsion (sudden change) does not move the boundary while accretion (gradual change) does.
What to do instead
Identify the water body classification and the controlling state law first. For tidal boundaries, confirm whether the state uses mean high water, ordinary high water, or another line. Distinguish accretion (gradual, boundary moves) from avulsion (sudden, boundary stays at the old line) and from erosion (boundary moves). Document the legal basis and the evidence (aerial photos, historical surveys) in the boundary report.
When preparing an ALTA/NSPS Land Title Survey, the candidate omits Table A optional items that were requested by the client, or includes items that were not requested, and does not show the required note about the surveyor's responsibility for the accuracy of the survey.
The ALTA/NSPS standards require the surveyor to state which Table A items were provided and which were not. Candidates often treat Table A as a checklist to complete in full or ignore it entirely, and they overlook the required notes and the certification language.
What to do instead
Read the client's written request and the current ALTA/NSPS standards. On the plat, list each Table A item and mark it as provided or not provided. Include the required note that the surveyor is responsible for the accuracy of the survey and that the survey was made in accordance with the standards. Verify the certification matches the requested form and that all easements, rights-of-way, and encumbrances are shown as required.
When computing a subdivision lot layout, the candidate uses the record plat bearings and distances without checking the closure of the parent tract, and then forces the lots to close by adjusting only the last lot, creating an irregular lot that does not match the approved plat.
Candidates focus on the individual lot geometry and forget that the parent tract must close within the allowable tolerance before lots are created. When the parent tract does not close, the error is pushed into the final lot, which is then not buildable or does not meet zoning requirements.
What to do instead
First, compute the closure of the parent tract from the deed or record plat and compare the misclosure to the applicable standard. If the parent tract does not close, resolve the discrepancy before designing lots. Design lots to meet zoning requirements (minimum area, width, setbacks) and distribute any necessary adjustments proportionally across all lots, not just the last one. Verify each lot closes and that the sum of lot areas plus rights-of-way equals the parent tract area.
When using a GNSS receiver for a boundary survey, the candidate reports coordinates from a single-base RTK solution without checking the horizontal and vertical precision, without confirming the coordinate system and epoch, and without a redundant check against a published control point.
RTK solutions can appear fixed while still containing errors from a bad base position, incorrect projection parameters, or a wrong geoid model. Candidates trust the fixed solution indicator and skip the independent check, especially under time pressure.
What to do instead
For every GNSS survey, record the coordinate system, datum, epoch, projection, and geoid model. Check the reported horizontal and vertical precision against the project standard. Occupy at least one published control point and compare the GNSS-derived coordinates to the published values. Use a second base or a network solution for redundancy on critical points. Do not accept a single-epoch fix for boundary corners; repeat observations and average.
When writing the legal description for a new parcel, the candidate describes the parcel by coordinates only, or by a bearing and distance that does not close, and omits the basis of bearing, the point of commencement, and the area.
Candidates treat the legal description as a simple list of calls and do not verify closure or include the elements that make the description locatable and unambiguous. Coordinates alone are not a sufficient legal description in most jurisdictions because they depend on a specific datum and epoch.
What to do instead
Write the description with a clear point of commencement tied to a monument or recorded point, a basis of bearing, and a series of calls that close within the allowable tolerance. Include the area, the parcel identifier, and the basis of the coordinates if used. Verify closure by computing the latitudes and departures. Have a second surveyor review the description for ambiguity before it is recorded.