NE Land Surveyor flashcards

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

Monument priority rule

In boundary retracement, undisturbed original monuments control over courses, distances, and area in the record; artificial monuments rank above courses and distances, which rank above area.

Adverse possession elements

Actual, open and notorious, exclusive, continuous for the statutory period, and hostile use. The statutory period is set by state law and commonly ranges from 10 to 20 years.

Accretion versus avulsion

Accretion is gradual, imperceptible deposition that moves a riparian boundary with the water. Avulsion is sudden, perceptible change that leaves the boundary where it was.

Meander line

A line run to compute the area of a fractional lot along a water body; it is evidential only and is not the boundary of record. The water boundary controls.

Double proportion corner

A method of restoring a missing section corner using two known corners on each of two intersecting lines, weighting the position by the record distances along those lines.

Horizontal curve tangent

The tangent distance from the PC or PT to the PI equals R times the tangent of half the central angle: T = R tan(Δ/2).

Vertical curve K value

K equals the curve length divided by the algebraic difference in grades in percent (K = L/|A|); it sets the rate of grade change per station.

Superelevation equation

In US customary units, e + f = V²/(15R), where e is superelevation rate, f is side friction factor, V is design speed in mph, and R is radius in feet.

Average end area volume

Earthwork volume equals the length between sections times the average of the two end areas: V = L(A1 + A2)/2, with a prismoidal correction for three-level sections.

Station equation

A notation where the stationing ahead differs from the stationing back at the same physical point, used at line changes or to remove accumulated stationing.

Distance-distance layout ambiguity

Two distances from two known control points intersect at two possible positions; the correct solution must be specified by side of line or by a third check measurement.

Height of instrument

HI equals benchmark elevation plus backsight reading. A stake elevation is then HI minus the foresight reading to that stake.

Layout check shot

An independent measurement of a laid-out point from a different instrument setup or control pair, used to detect orientation and coordinate blunders before construction proceeds.

Stake offset sign convention

Offset equals measured distance minus design distance; the sign and reference side must be recorded on the stake and in the field book to prevent reversed corrections.

Combined factor

Grid factor multiplied by elevation factor; grid distance equals ground distance times the combined factor, correcting for projection scale and height above the ellipsoid.

Geoid height relation

Orthometric height H equals ellipsoid height h minus geoid height N: H = h − N. Geoid models such as GEOID18 supply N for a region.

Grid convergence

The angle between grid north and true north at a point; grid azimuth equals geodetic azimuth plus convergence, and convergence varies with longitude from the central meridian.

UTM central scale

Universal Transverse Mercator uses 6-degree zones with central meridian scale factor 0.9996 and false easting 500,000 meters, so scale is not unity away from the meridian.

Ellipsoid flattening

Flattening f relates semi-major axis a and semi-minor axis b as b = a(1 − f); eccentricity squared equals 2f − f².

Topology validation

Rules that detect gaps, overlaps, dangling nodes, and self-intersections in vector data; violations are reported before analysis so area and network results remain valid.

Raster resampling methods

Nearest neighbor preserves categorical values; bilinear and cubic interpolation produce smooth continuous surfaces but can create values not present in the source data.

Equal-area projection use

Equal-area projections preserve area relationships, making them suitable for density and land-cover statistics; conformal projections instead preserve local shape and angles.

Geographic CRS buffer error

Buffering in a geographic coordinate system uses degrees, so buffer width varies with latitude and is distorted; buffer in an appropriate projected CRS instead.

Chart datum MLLW

Mean Lower Low Water is the reference for soundings and charted depths in US waters; charted heights of bridges and clearances reference Mean High Water.

Multibeam swath width

Approximate swath width equals twice the depth times the tangent of half the beam angle; resolution and coverage degrade with depth and at outer beams.

Sound velocity error

Incorrect sound speed at the transducer refracts beams, producing systematic depth bias or a bowl-shaped artifact; a measured velocity profile is required.

Tidal datum epoch

Tidal datums are computed over a 19-year National Tidal Datum Epoch; short-term observations are reduced by comparison with a long-term control station.

Rational method

Peak discharge Q equals C times i times A, with C the runoff coefficient, i rainfall intensity, and A drainage area; time of concentration sets the storm duration.

Detention versus retention

Detention temporarily stores stormwater and releases it at a controlled rate; retention holds water permanently, as in a wet pond, without direct discharge.

Right-of-way versus easement

Right-of-way is dedicated land for public access and improvements; an easement grants specific use rights over land without transferring title.

Relief displacement

On a vertical photograph, displacement d equals r times h divided by H, where r is radial distance from the principal point and h is object height.

Photographic scale

Scale equals focal length divided by flying height above ground (S = f/H); a larger scale means a smaller denominator and more ground detail.

LiDAR RMSEz

Vertical accuracy of a LiDAR-derived surface is reported as root mean square error in z, computed against independent surveyed checkpoints rather than the point cloud.

NDVI formula

Normalized Difference Vegetation Index equals (NIR − Red)/(NIR + Red), ranging from −1 to 1; healthy vegetation typically returns values above 0.3.

Recording act notice

Under a notice statute, a later purchaser who takes without notice of a prior unrecorded interest prevails; race-notice statutes add the requirement to record first.

Easement by necessity

An implied easement arising when a parcel is landlocked by severance from a common owner; it requires unity of title and strict necessity of access.