CA Surveying flashcards

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

Monument controls over distance

In deed construction, natural and artificial monuments called for in the deed outweigh recorded courses, distances, and stated area, which are the least reliable calls.

Proportional conveyance doctrine

When a grantor divides a tract among several grantees by deeds calling for the same exterior monuments, any excess or deficiency is shared in proportion to what each deed conveys.

Accretion versus avulsion

Accretion is the gradual, imperceptible deposit of land by water and belongs to the riparian owner; avulsion is a sudden change such as a flood cutoff and does not move the boundary.

Thread of a non-navigable stream

The centerline of a non-navigable stream; riparian deeds generally carry ownership to this line, making each owner a proprietor of the bed unless the deed or statute says otherwise.

Meander line

A traverse run to approximate the bank of a body of water for computing area; it is not a boundary of record and does not limit the water frontage granted by a riparian deed.

Adverse possession elements

Actual, open and notorious, exclusive, continuous, and hostile use of another's land for the statutory period, which can vest title in the possessor under state law.

PLSS section area

In the Public Land Survey System a normal section contains 640 acres, or one square mile; a quarter section is 160 acres and aliquot halves and quarters subdivide further.

Lost corner proportioning

A lost corner cannot be recovered from physical evidence, so it is re-established by proportioning record distances between the nearest existing original corners along the line.

Arc definition degree of curve

The central angle subtended by a 100-ft arc, giving radius R = 5729.58/D feet; this is the standard definition for highway horizontal curves in the United States.

Tangent distance horizontal curve

T = R tan(Δ/2), the distance from the PC or PT to the point of intersection, where R is the curve radius and Δ is the central deflection angle.

Middle ordinate

M = R(1 − cos(Δ/2)), the distance from the midpoint of the long chord to the midpoint of the curve; the external E = R(sec(Δ/2) − 1) runs to the PI.

Deflection angle per station

For a curve of degree D, the deflection from the tangent to a point at arc length l is δ = l·D/200 degrees, so one full 100-ft station deflects D/2.

Vertical curve K value

K = L/A, the horizontal length in feet per 1 percent algebraic change in grade; a larger K gives a flatter curve and longer available sight distance.

Average end area volume

V = L(A1 + A2)/2 for the volume between two parallel sections of areas A1 and A2 separated by distance L; the prismoidal correction improves accuracy for varying sections.

Combined scale factor

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

Traverse relative precision

Total linear misclosure divided into the total traverse length, expressed as 1:N; a 0.10-ft closure over 5,000 ft of traverse gives 1:50,000.

Geoid undulation relation

h = H + N, where h is ellipsoidal height obtained from GNSS, H is orthometric height above the geoid, and N is the geoid undulation, all in the same units.

GRS80 ellipsoid parameters

Semi-major axis a = 6,378,137 m with inverse flattening 1/f = 298.257222101; WGS84 uses the same axis but 1/f = 298.257223563, a negligible difference.

UTM zone geometry

Sixty zones each 6 degrees of longitude wide, with a central meridian scale factor of 0.9996, a false easting of 500,000 m, and grid coordinates increasing north and east.

State Plane projection choice

Lambert Conformal Conic serves zones with east-west extent and Transverse Mercator serves north-south zones; both keep scale error small inside the zone boundary.

Curvature and refraction correction

In differential leveling subtract 0.0206 D² ft when D is in hundreds of feet, or 0.0675 K² m when K is in kilometers, from the rod reading.

Elevation factor

R/(R + h), where R is mean Earth radius and h is height above the ellipsoid; it reduces ground distances to the reference surface and is part of the combined factor.

Least squares adjustment

A stochastic adjustment minimizing the weighted sum of squared residuals, producing adjusted coordinates plus standard deviations and error ellipses for each station in the network.

Azimuth versus bearing

Azimuth is a clockwise angle from north spanning 0 to 360 degrees; a bearing is an acute angle from the north or south meridian with a quadrant letter, never exceeding 90 degrees.

Vertical photo scale

S = f/H, the ratio of camera focal length to flying height above mean ground; a 6-inch focal length flown at 6,000 ft yields a scale of 1:12,000.

Relief displacement

d = r·h/H, where r is radial distance from the principal point, h is object height, and H is flying height above datum; tall objects displace outward from the photo center.

Contour line rules

Contours never cross except at an overhang, run perpendicular to the steepest slope, and are closely spaced on steep ground and widely spaced on gentle ground.

DEM versus DSM

A DEM represents bare-earth elevations, a DSM includes vegetation and structures, and a DTM is a bare-earth model built from breaklines and mass points.

Vertical exaggeration

The horizontal map scale divided by the vertical scale; a 1:2,000 horizontal scale combined with a 1:200 vertical scale produces ten times exaggeration.

Representative fraction

A unitless scale ratio such as 1:24,000, meaning one map unit equals 24,000 ground units; 1 inch = 2,000 feet is equivalent to 1:24,000.

TIN interpolation

A triangulated irregular network fits planes to triangles of mass points and breaklines, honoring ridges and stream channels better than a uniform grid interpolated by bilinear methods.

ASPRS accuracy statistic

At 95 percent confidence, horizontal RMSE is multiplied by 1.7308 and vertical RMSE by 1.96 to state the tested positional accuracy of a map product.