LAND SURVEY TERMINOLOGY

GLOSSARY OF U.S. BUREAU OF LAND MANAGEMENT SURVEYING AND MAPPING TERMS C

Land Survey Terms, A convenient source for our clients and website visitors

C

C/A CODE- (GPS)- A binary code known by Civilian/Access. It is a standard spread spectrum GPS pseudorandom noise code modulated on the L1 carrier using binary biphase modulations.

COMPUTER-AIDED DESIGN (CAD) – COMPUTER-AIDED DESIGN AND DRAFTING (CADD)- (SURVEY)- is the use of computer technology for the process of design, design-documentation and drafting.

CC – (PLSS)- Closing Corner.

CH, CHS – (SURVEY)- Chain, Chains.

CRT – Cathode ray tube.

CALIBRATED FOCAL LENGTH (CFL) – An adjusted value of the equivalent focal length so computed as to
distribute the effect of lens distortion in a desired manner over the entire field used in a camera.

CALIBRATION – The act or process of determining certain specific measurements in a camera or other instrument
or device for comparison with a standard or for purpose of record.

CALIBRATION, CAMERA – The determination of 1) the calibrated focal length; 2) the location of the principal
point with respect to the fiducial marks; 3) the point of symmetry; 4) the resolution of the lens; 5) the degree of
the flatness of the focal plane; and 6) the effective lens distortion in the focal plane of the camera which is
referred to the particular calibrated focal length. In a multiple-lens camera, the calibration also includes the
determination of the angles between the component perspective units.

CALIBRATION CONSTANTS – The results obtained by calibration which give the relationship of the principal
point to the fiducial marks of a camera and the calibrated focal length of the lens-camera unit.

CAMERA, AERIAL – A camera specifically designed for use in aircraft. The prefix aerial is not essential where
the context clearly indicates an aerial camera rather than a ground camera.

CAMERA AXIS – A line perpendicular to the focal plane of the camera and passing through the interior
perspective center or emergent nodal point of the lens system.

CAMERA STATION – The point in space occupied by the camera lens at exposure.

CANAL – 1) An artificial watercourse cut through a land area for navigation, irrigation. 2) A long narrow arm of the
sea extending far inland.

CANTILEVER EXTENSION – (USGS) Phototriangulation from a controlled area to an area of no control. The
procedure may be progressive, starting from the control, or it may be a simultaneous mathematical procedure.

CANYON or CAÑON – A gorge, relatively narrow but of considerable size, bounded by steep slopes. It has been
formed by a river cutting through the soft rocks of an arid region.

CAP – A metal or plastic cover used for rebar or piping. The cap is typically stamped with an identifier, such as the surveyor’s license number.

CAPE – 1) A point of land extending into the sea or a lake; a headland. 2) A relatively extensive land area jutting
seaward from a continent or large island which prominently marks a change in, or interrupts notably, the coastal
trend.
CARRYING CONTOUR – (USGS) A single contour line representing two or more contours; used to show vertical
or near vertical topographic features, such as cliffs, cuts and fills.
CARTOGRAPHIC LICENSE – (USGS) The freedom to modify manuscript information in order to improve the
clarity of the map.
CARTOGRAPHY – The art, science and technology of expressing graphically, by maps, charts, three-dimensional
models and globes, the known physical features of the earth or any heavenly body, at any scale. In particular,
cartography is concerned with all phases of map finishing, including the designing of format and symbolization;
drafting, editing, and proofing of map content; and specifying requirements for reproduction.

CASED ROAD – A double line symbol for a road on a map-usually major highways.

CATHODE-RAY TUBE – A vacuum tube that generates a focused beam of electrons which can be deflected by
electric and/or magnetic fields. The assembly contains an electron gun arranged to direct a beam upon a
fluorescent screen. Scanning by the beam can produce light at all points.

CENTERING DEVICE, DIAPOSITIVE – See DIAPOSITIVE CENTERING DEVICE.

CENTER OF RADIATION – The selected point on a photograph from which radials are drawn or measured.

CENTER, PHOTOGRAPH – The center of a photograph as indicated by the images of the fiducial marks of a
camera. In a perfectly adjusted camera the photograph center and the principal point are identical.

CENTRAL MERIDIAN – The meridian, usually passing near the center of the area, used as the Y or N axis in a
plane-coordinate or grid system. To avoid negative coordinates in the system, this meridian is usually assigned a
large X or E value.

CENTRAL PERSPECTIVE RAY – The ray from the external perspective center to the object point whose image
is located at the principal point.

C FACTOR – An empirical value which expresses the contour plotting capability of a given stereoscopic system,
generally defined as the ratio of flight height to the smallest contour interval accurately plottable. Not a constant
but dependent on conditions present, it is used in determination of flying height or as a rough comparison of
photogrammetric systems.

CHART – (USGS) A special-purpose map generally designed for navigation. The term “chart” is applied chiefly to
maps made primarily for nautical and aeronautical navigation and to maps of the heavens, though the term is
sometimes used to describe other special-purpose maps.

CHECKED ELEVATION – An elevation determined by two or more independent sets of measurements, or by a
closed loop, in which the results agree within a specified limit. Results are printed in black on USGS maps.

CHECK PROFILE – A profile plotted by use of field survey measurements to check a profile plotted using
measurements of position and elevation from a topographic map.

CHICAGO ROD – A two piece leveling rod with a telescopic joint.

CIRCUIT – A series of connected survey lines that form a closed loop; also, a line or series of lines connecting two
fixed points.

CIRCUIT CLOSURE – The discrepancy between the algebraic sum of the differences in elevation between
junction points in a leveling circuit and the theoretical value of zero.

CIRCULAR LEVEL – A spirit level with the inside surface of its upper part ground spherical to form a circular
bubble, and with graduations consisting of concentric circles, for application where high precision is not
required.

CLASSICAL POINTS – Six symmetrically selected image points located within the neat model at which Y
parallax is removed during relative orientation of the photographs. Four of the points are near the model corners;
the other two are near the X-X axis near the model boundary. See PASS POINTS.

CLOSED TRAVERSE – A traverse which starts and ends upon the same station or upon stations of known
position.

CLOSING THE HORIZON – Measuring the last angle of a series of angles around a station.

CLOSURE – 1) The process of measurement in a closed figure for a check on horizontal or vertical precision. 2)
(USGS) A misclosure. See JUNCTION CLOSURE, HORIZON CLOSURE and TRIANGLE CLOSURE.

COASTAL PLAIN – A plain which borders the sea coast, and extends from the sea to the nearest elevated land. It
is sometimes formed through denudation by the sea, the beach being later raised by earth movement to form a
plain, frequently known as a Raised Beach, or by deposition of solid matter at their mouths by rivers.

COASTLINE – The line that separates the land surface and the water surface of the sea or ocean. See BEACH and
BEACH*.

COATED LENS – A lens coated to reduce light reflection from its surface and for selectively absorbing light of a
particular wavelength (color) so as to prevent it from passing through the lens.

COINCIDENCE – 1) The alinement if diametrically opposed index marks to form a continuous line under the
reading microscope of a theodolite. 2) The alinement of the images of opposite ends of a level bubble.

COLLIMATE – 1) To render parallel to a certain line or direction, to render parallel, as rays of light; to adjust the
line of sight or lens axis of an optical instrument so that it is in its proper position relative to other parts of the
instrument. 2) To adjust the fiducial marks of a photogrammetric camera so that they define the principal point.
Also called adjustment for collimation.

COLLIMATION – The act of making a collimation adjustment.

COLLIMATION ADJUSTMENT – The process of bringing the line of collimation of a telescope into close
agreement with the collimation axis. Also termed adjustment for collimation.

COLLIMATION AXIS – The line through the second nodal point of the objective (object glass) perpendicular to
the horizontal axis of a transit or perpendicular to the vertical axis of a level.

COLLIMATION, ERROR OF – The angle between the line of collimation (line of sight) of a telescope and its
collimation axis.

COLLIMATION, LINE OF – The line through the second nodal point of the objective (object glass) of a telescope
and the center of the reticle.

COLLIMATION PLANE – The plane described by the collimation axis of a telescope of a transit when rotated
around its horizontal axis.

COLLIMATOR – A fixed telescope with crosshairs in its focus, used to adjust a second telescope by looking
through it in a reverse direction with the latter so that images of the crosshairs are formed in the focus of the
second telescope, as if they originated in a distant point.

COLOR COMPOSITE IMAGE – In landsat imagery, a color negative, transparency, or print produced from bulk
or precision black-and-white triplet sets.

COLOR ENHANCEMENT – Utilization of contrasting colors (rather than differences in grey values) to indicate
subtle changes in film density. Can be applied in single or multi-emulsion situations.

COLOR PROOF – A multicolor print made by whirling or rubbing color proof sensitizer on a proof sheet and
making consecutive exposures through the scribed features. Each color requires separate sensitization which is
applied over the previous color print to form the composite multicolor proof.

COLOR SEPARATION – The preparation of separate drawings for each type of map data to be reproduced in a
separate color.

COLOR SEPARATION DRAWING – Separate manuscripts prepared for each color of the completed map.

COLOR-SEPARATION GUIDE – A print of a manuscript that provides copy for final drafting, scribing, or
stickup of selected data.

COMBINATION GRAVER – A swivel graver which may be converted to a rigid graver for scribing.

COMPARATOR – 1) An instrument or apparatus for measuring a dimension in terms of a standard. 2) An
instrument for comparing standards of length; for subdividing such standards; or for determining a standard
length of a measuring device. 3) An optical instrument, usually precise, for measuring rectangular or polar
coordinates of points on any plane surface, such as a photographic plate.

COMPASS SURVEY – A transverse survey which relies on the magnetic needle for orienting the sequence as a
whole or for determining the bearings of lines individually.

COMPENSATING ERROR – An error that tends to offset a companion error and thus obscure or reduce the effect
of each.

COMPENSATION PLATE – See CORRECTION PLATE.

COMPILATION – 1) The production of a new or improved map (or portion of a map) from existing maps, aerial
photographs, surveys, new data, and other sources. 2) The production of a map (or portion of a map) from aerial
photographs and geodetic control data, by means of photogrammetric instruments.

COMPILED MAP – A map incorporating information collected from various sources, not developed by surveys
made for the map in question. Most small-scale maps of large areas are compiled maps.

COMPLETION – Obtaining field information needed to edit and publish a map from a compiled manuscript. See
FIELD COMPLETION and COMPLETION SURVEY*.

COMPOSITE – A print containing the reproducible information from two or more color separation drawings
surprinted in register.

COMPUTER MAPPING – See DIGITAL MAPPING.

CONCLUDED ANGLE – An interior angle between adjacent sides of a polygon which is obtained by subtracting
the sum of all the other interior angles of the figure from the theoretical value of the sum of all interior angles.

CONFLUENCE – A junction or flowing together of streams; the place where streams meet.

CONFORMAL – Having the map scale at any one point the same in both directions. See CONFORMALITY.

CONFORMALITY – The unique property of conformal map projections, in which all small or elementary figures
on the surface of a sphere retain their original shapes on the map. See ANGULAR DISTORTION.
CONFORMAL MAP PROJECTION – See CONFORMALITY.

CONGRUENCING – Process by which two images or two digital images of a multi-image set are transformed so
that the size and shape of any object on one photograph is the same as the size and shape of that object on the
other photograph.
CONJUGATE IMAGE POINTS – Unique, selected objects appearing in each of two or more photographs. See the
preferred term CORRESPONDING IMAGE POINTS.

CONSTANT ERROR – A systemic error which is the same in both magnitude and sign throughout a given series
of observations, such as an index error of an instrument.
CONSTRUCTION SURVEY – The survey measurements made for design information, stakeout for construction
or for surveys during progress of construction as well as following completion of the work for quantity
determination.
CONTACT PRINT – A photographic print produced by the exposure of a sensitized emulsion in contact with the
emulsion of a negative or positive transparency.
CONTACT PRINTER (USGS) – 1) Any machine which reproduces a photographic image using emulsion contact.
2) A diapositive printer in which the sensitized surface of the diapositive plate is placed in direct contact with
that of the aerial negative to produce an exact positive copy of the negative.
CONTINENT – Large land mass rising more or less abruptly above the deep ocean floor; includes marginal areas
that are shallowly submerged.
CONTINENTAL APRON – The gentle incline at the base of the continental slope leading to the deep oceanic
basins.
CONTINENTAL MARGIN – The zone separating the emergent continents from the deep sea bottom; generally
consists of continental shelf, continental slope and continental rise.
CONTINENTAL SHELF – The submerged portion of a continent which slopes gently seaward from the low-water
line to a point where a substantial break in grade occurs, at which point the bottom slopes seaward at a
considerable increase in slope until the great ocean depths are reached. The point of break defines the “edge” of
the shelf, and the steeper sloping bottom the “continental slope.” Conventionally, the edge is taken at 100
fathoms (or 200 meters) but instances are known where the increase in slope occurs at more than 200 or less than
65 fathoms. See OUTER CONTINENTAL SHELF.
CONTINENTAL SLOPE – Continuously sloping portion of the continental margin with gradient of more than 1 to
40, beginning at the outer edge of the continental shelf and bounded on the outside by a rather abrupt decrease in
slope where the continental rise begins at depths ranging from about 4,500 to 10,000 feet; formerly considered to
extend to abyssal plains.
CONTINENTAL TALUS – The steep slope from the lower edge of the continental shelf into the ocean depths. It is
characterized by a marked change in gradient and usually begins at a depth of approximately 100 fathoms.
CONTINUOUS-STRIP PHOTOGRAPHY – Photography of a strip of terrain in which the image remains
unbroken throughout its length along the line of flight. See SONNE CAMERA.
CONTOUR – An imaginary line on the ground all points of which are at the same elevation above or below a
specified datum surface. See APPROXIMATE CONTOUR, CARRYING CONTOUR, DEPRESSION
CONTOUR, INDEX CONTOUR, INTERMEDIATE CONTOUR, SUPPLEMENTAL CONTOUR and
UNDERWATER CONTOUR.
CONTOUR INTERVAL – The difference in elevation between adjacent contours.
CONTOUR MAP – See TOPOGRAPHIC MAP.
CONTRAST – Difference between tones on a photograph; the variation in brightness of different parts of a negative
or positive.
CONTRAST IMPROVEMENT – Image alternation which increases the grey-tone intensity differences.
CONTROL INDEX MAP (USGS) – A map of an area showing by suitable symbols the location of all control lines
or stations of a designated category, and indicating the file location of the related control data. See GEODETIC
CONTROL DIAGRAMS.
CONTROLLED MOSAIC – A mosaic oriented and scaled to horizontal control; usually assembled from rectified
photographs.
CONTROL BASE (USGS) – A surface upon which the map projection and ground control are plotted and upon
which pass points resulting from aerotriangulation have been plotted or marked. See BASE SHEET.
CONTROL, PHOTO – Any station in a horizontal and vertical control system that is identified on a photograph
and used for correlating the data shown on that photograph; also termed photocontrol point, picture control point,
and ground control point.
CONTROL POINTS – Any station (in a horizontal and/or vertical-control system) that is identified on a
photograph and used to aid in fixing the attitude and/or position of a photograph or group of photographs.
CONTROL STRIP – 1) A strip of aerial photographs taken to aid planning and accomplishing later aerial
photography, or to serve as control in assembling other strips. 2) A strip of film used for control of exposure,
development, or both.
CONTROL SURVEY – A survey which provides horizontal or vertical position data for subordinate surveys or
mapping.

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CONTROL SURVEY CLASSIFICATION – A series of designations to classify control surveys according to their
precision and accuracy. The highest prescribed order of control surveys is designated first order; the next lower
prescribed classification, second order; the lowest, third order. Specifications issued by the Bureau of the Budget
in 1958 establish three main orders of geodetic control, with additional sub-divisions of classes in some of them.
Surveys which fail to meet one of the three preceding specifications are called fourth order although they meet
no prescribed standards.
CONVERGENCE OF EVIDENCE – Bringing together several kinds of evidence so that a conclusion may be
drawn from all available data.
CONVERGENCE OF MERIDIANS – The drawing together of the geographic meridians in passing from the
Equator to the Pole.
CONVERGENT PHOTOGRAPHY – Aerial photography with the camera (or cameras) intentionally tilted so that
the central perspective ray of one exposure is inclined to that of an adjacent station.
COORDINATES – A set of numbers used in specifying the location of a point.
COORDINATE SYSTEM – A mathematically defined method for specifying the locations of points. Distances or
angles from suitable references located the points within the system. See GEODETIC COORDINATES,
GEOGRAPHIC COORDINATES, PLANE COORDINATES, SPHERICAL COORDINATES, STATE
COORDINATE SYSTEMS, STATE PLANE COORDINATES and UNIVERSAL TRANSVERSAL
MERCATOR.
COORDINATE TRANSFORMATION – Mathematical conversion of coordinate values from one system to
another.
COORDINATOGRAPH – An instrument by which the X and Y coordinates of points and/or lines are plotted on a
plane, such as in compiling maps or in plotting control points.
COPLANER – Lying in the same plane.
COPYING CAMERA – A precision camera used in the laboratory for reproduction purposes. Also called process
camera.
CORNER, FOUND – A term adopted by the U. S. Geologic Survey to designate an existent corner of the public-
land surveys which has been recovered by field investigation. See CORNER*.
CORRECTION – A quantity which is applied to an observation or function thereof to diminish or eliminate the
effects of errors and obtain an improved value of the observation or function. It is also applied to reduce an
observation to some arbitrary standard.
CORRECTION PLATE – A glass plate having a surface ground to a predetermined shape for insertion into an
optical system to compensate for known systemic errors in the photogrammetric system.
CORRESPONDENCE – The condition that exists when corresponding images on a pair of photographs lie in the
same epipolar plane; the absence of y parallax. See Y PARALLAX.
CORRESPONDING IMAGE POINTS – Unique objects appearing in each of two or more photographs selected to
correlate the photograph.
COULEE – 1) A short, blocky, steep-sided lava flow, generally of glassy rhyolite or obsidian, issuing from the flank
of a volcanic dome or from the summit crater of a volcano. 2) The term coulee is generally applied throughout
the northern tier of states to any steep-sided gulch or water channel and at times even to a stream valley of
considerable length.
COURSE – 1) The bearing or, azimuth and length of a line, considered together. 2) The azimuth or bearing of a line
along which a ship or aircraft is to travel or does travel, without change of direction; the line drawn on a chart or
map as the intended track. The direction of a course is always measured in degrees from the true meridian, and
the true course is always meant unless it is otherwise qualified; e.g., as a magnetic or compass course. 3) A route
on the earth along which a river flows; the river itself.
COVE – A small bay or open harbor.
COVERAGE – 1) Inclusion of an area within overlapping aerial photos. 2) A measure of the amount of area
covered in an aerial photograph, usually expressed as square miles per frame.
CRAB – A photographic condition caused by failure to orient the camera to the flight line resulting in photo edges
not parallel to the air base.
CREEK – 1) A steam of less volume than a river. 2) A small steam of intermittent flow.
CRESCENT BEACHES – Crescent-shaped beaches concave toward the sea which form at the heads of bays and at
the mouths of streams entering these bays along hilly and mountainous coasts.
CREST – The summit land of any eminence; the highest natural projection which crowns a hill or mountain, from
which the surface dips downward in opposite directions.

CRITICAL POINT – A peak or high ground with abrupt local relief requiring investigation in planning aerial
photography to avoid “hidden ground.”
CRITICAL SURFACE – A valley terrain of cylindrical form with the air base lying on or near the surface of the
cylinder as extended into the air. Orientation becomes indeterminate.
CROSS SECTIONING, DIGITAL – The determination of a vertical section of terrain in which the measurements
are stored as numerical values. See DIGITIZING.
CUESTA – A ridge, or belt of hilly land, formed on gently dipping rock strata (e.g. on a coastal plain) from the
more durable layers, which resist denudation better than the weaker layers, and are thus left behind as uplands; it
has a gentle dip slope on one side, and a relatively steep scarp slope on the other.
CULTURE – Those features of the terrain that have been constructed by man, such as roads, trails, buildings and
boundary lines.
CULVERT – A structure carrying traffic over a watercourse having a 10 feet or less clear span. Usually a pipe
section.
CURVES – Curved rulers, termed irregular curves, or French curves, used for drawing curved lines. The patterns for
these curves are laid out in parts of ellipses and spirals or other mathematical curves in various combinations.
Curves for drawing circular curves are highway curves.
CUT – 1) Depth to which material is to be excavated (cut) to bring the surface to a predetermined grade. Therefore,
the cut is the difference in elevation of a surface point and a point on the proposed subgrade vertically below it.
2) The name applied to the excavated area itself. 3) A graphic ray from a known plane table position to an
unknown position. See CUT*.
CUT TAPE – A survey tape on which the minor graduation are placed only between zero and one unit. See ADD
TAPE.

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