NSPS CST Level III flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Angular misclosure formula

For an n-sided closed traverse, the sum of interior angles should equal (n-2) times 180 degrees. The difference between measured and theoretical sums is the angular misclosure, distributed equally before azimuths are computed.

Traverse linear misclosure

The linear misclosure is the square root of the sum of squared latitude error and departure error. Relative precision equals total traverse length divided by that misclosure, reported as a ratio such as 1:10,000.

Latitude and departure

Latitude equals distance times the cosine of the azimuth; departure equals distance times the sine of the azimuth. North and east values are positive, south and west negative, and their sums reveal closure error.

Curvature and refraction correction

The combined correction in feet is 0.0206 times the square of the distance in thousands of feet. Refraction bends the line of sight downward, offsetting roughly one-seventh of the curvature effect.

Average end area volume

Volume equals length times the average of the two end areas. It is accurate for gradually changing sections but overestimates volume where the cross section changes abruptly, such as at a culvert.

Prismoidal volume formula

Volume equals length times (A1 plus 4Am plus A2) divided by six, where Am is the mid-section area. It is more accurate than average end area for rapidly changing sections.

Cut and fill stake marking

On a grade stake, the cut is written above the grade line and the fill below it. The stake also shows station, offset distance, and the elevation difference to finished grade.

Two-face angle observation

Observing the same direction in face left and face right and averaging the readings cancels collimation error, trunnion axis error, and horizontal circle eccentricity. The spread between faces is a check.

Balanced sight distances

Keeping backsight and foresight distances nearly equal cancels residual instrument centering error and collimation error in a traverse. Unbalanced long foresights amplify the effect of any setup error.

Resection geometry weakness

Resection from three known points gives position and orientation, but points clustered on one side produce weak geometry. Small residuals then understate the true positional uncertainty of the setup.

RTK fix versus float

A fixed solution has resolved carrier-phase ambiguities and is typically centimeter-level. A float solution has unresolved ambiguities and is roughly an order of magnitude less precise, unsuitable for boundary or control work.

Dilution of precision

DOP expresses how satellite geometry multiplies ranging error. PDOP combines horizontal and vertical effects, HDOP covers horizontal, VDOP covers vertical, and a high value invalidates an otherwise clean fix.

Leveling loop misclosure

A leveling loop must return to its starting elevation within a tolerance, often scaled as a constant times the square root of the loop length in miles. Misclosure is distributed in proportion to accumulated distance.

Monument stability for control

Control should be set on deep-seated, stable marks rather than pavement or backfill. Existing control is re-observed at project start so movement since the last epoch is detected before it propagates.

Azimuth and reference marks

An azimuth mark fixes the orientation of a primary station, while reference marks allow the station to be recovered by intersection if the monument is disturbed. Both are tied by measured bearing and distance.

Offset staking convention

Stakes are set a constant distance off the design line so equipment does not disturb them, and the offset is written on the stake. The offset must be reapplied when the stake is used to set the work.

Slope stake offset

The horizontal offset from the design line to the catch point equals the vertical difference times the side slope ratio. A 4-foot fill at 2:1 requires an 8-foot horizontal offset.

Trigonometric leveling grade check

Elevation difference equals horizontal distance times the tangent of the vertical angle, plus instrument height, minus target height. Curvature and refraction are negligible on short construction shots.

One-call utility tolerance zone

Before excavation, the one-call service is notified and the marked tolerance zone around each utility is respected. Markings expire, so long projects require refreshed locate requests before digging resumes.

Field note correction practice

Field notes are written in ink; errors are struck through and initialed rather than erased. Notes may be produced as evidence, and erasures invite challenges to the integrity of the record.

Record evidence hierarchy

Written record documents control over monuments, monuments control over courses and distances, and courses and distances control over area. This ordering resolves conflicts among deed calls and physical evidence.

Deed closure check

Convert each bearing and distance to latitude and departure, sum them, and compare the resultant to the perimeter. A large misclosure points to a transcription error or a misread bearing rather than a field problem.

Combined factor and ground distance

Grid distance times the combined factor equals ground distance, where the combined factor is the state plane scale factor multiplied by the elevation factor. Distances must be converted before comparing to field measurements.

Shoelace area formula

Twice the area equals the sum of X(i) times Y(i+1) minus the sum of Y(i) times X(i+1), taken around the closed figure. The result is signed, so the absolute value is used.

Least squares residuals

A residual is the adjusted value minus the observation. Standardized residuals much larger than about three suggest an outlier worth investigating, but deletion requires justification, not convenience.

Adjustment degrees of freedom

Degrees of freedom equal the number of observations minus the number of unknowns. A network with zero redundancy cannot detect blunders and provides no independent check on the solution.

Reference variance interpretation

A least squares adjustment reports a reference variance, ideally near 1.0. Values far from 1.0 mean the assumed measurement weights do not match the actual data, so the uncertainty estimates are unreliable.

Uncertainty propagation for sums

For a sum or difference of independent measurements, variances add. Total uncertainty is the square root of the sum of squared individual uncertainties, never the simple sum of absolute values.

Metadata for a deliverable

A defensible dataset states datum and epoch, coordinate system and units, survey date, instrument and method, positional uncertainty, and the responsible surveyor. Missing metadata makes the dataset incomplete.

Metes and bounds components

A description includes a commencement, a point of beginning, a series of calls giving bearing, distance, and monument, and a closing call returning to the point of beginning. Each call must be internally consistent.

Scrivener error in a description

When a deed fails to close by a significant amount, a transcription error is likely. The office documents the discrepancy and the basis for any correction instead of silently adjusting a call.

Seal and professional responsibility

The surveyor's seal attests to personal responsibility for the work. Applying it to work the licensee did not direct or review is a violation even when the technical content is accurate.