LAND SURVEY TERMS

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

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

I

I. – Island

IA – Iowa; Infrastructure Analyst (BaySys Technologies Inc.)

IA (Land Status Records) – Indian Allotment.

IACWD – Interagency Advisory Committee on Water Data

IAEA – International Atomic Energy Agency

IAEG – International Assn. of Engineering Geologists

IAEGS – Institute for Advanced Education in Geospatial Sciences

IAG – International Assn. of Geodesy

IAGS – Inter-American Geodetic Survey

IAH – International Association of Hydrogeologists

IAS – Indian Allotment Survey.

IBID. – An abbreviation for “ibidem,” a Latin term meaning “in the same place,” “in the same book,” “on the same
page,” etc. It usually refers to an immediately preceding citation with an identical page reference. See ID.

IBLA – Interior Board of Land Appeals. See BOARD OF LAND APPEALS.

IC (Land Status Records) – Interim Conveyance.

ID. – Abbreviation for “idem,” a Latin term meaning “the same.” It indicates an immediately preceding citation but a
different page reference. See IBID.

ID – Idaho.

ID (Land Status Records) – Interior Decisions.

IDEN (Land Status Records) – Identify, Identification.

ID EST – That is. Commonly abbreviated “i.e.”

I.E. – That is. The common abbreviation for the Latin “id est.”

IL – Illinois.

IL (Land status Records) – Indemnity list.

ILL. – Illinois.

INC (Land Status Records) – Including, Inclusive.

IN – Indiana.

IND. – Indiana.

IND FEE (Land Status Records) – Indian Fee.

IND HD TR PAT (Land Status Records) – Indian homestead trust patent.

IND MER (Land Status Records) – Indian Meridian

IND RES (Land Status Records) – Indian Reservation.

IND TR (Land Status Records) – Indian Trust.

INTPR (Land Status Records) – Interpretation.

IMC – Image Motion Compensation.

IPS – Iron Pipe Size. Also plural for Iron Post.

IS (Land Status Records) – Indemnity selection.

IT (Land Status Records) – Isolated tract.

IR – Infrared.

ICONOMETRY – The process of conducting a plan and elevation from the perspective is termed iconometry. It is the reverse of drawing a perspective form plan and elevation. As applied to photographic surveying, iconometry is the process of making a map from photographs.

IDENTIFICATION POSTS – Wood or metal upright stake marked or tagged to help in recovery of survey stations.
IMAGE COMPRESSION – A remote sensing operation which preserved all or most of the information in the image and which reduces the amount of memory needed to store an image or the time needed to transmit an
image.
– Any one of a group of operations which improve the detectability of the targets of
interest. These operations include, but are not limited to, contrast improvement, edge enhancement, spatial filtering and noise suppression, image smoothing and image sharpening.
IMAGE-MOTION COMPENSATION – A device installed with certain aerial cameras to compensate for the forward motion of an aircraft while photographing ground objects. True image-motion compensation must be introduced after the camera is oriented to the flight track of the aircraft and the camera is fully stabilized.
IMAGE POINT – The image on a photograph corresponding to a specific point on the ground.
IMAGE RAY – Straight line from a ground object, through the camera lens, to the image on the photograph.
IMAGERY – Representation or reproduction of objects recorded on photographic emulsions; visual representation of energy recorded by remote sensing instruments.
IN-AND-OUT STATION (USGS) – A recoverable but unoccupied station incorporated into a traverse by recording a fictitious deflection angle of 180° to reverse the azimuth of the course leading into it, so that the next station coincided with the preceding station and the in-and-out station is used as the backsight for continuing the traverse. In the computations it is treated as an ordinary station in the traverse.
INDEX CONTOUR – A contour line shown distinctively for easy identification and generally labeled with the elevation value.

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INDEX CORRECTION – A correction applied to the reading from any measuring device to compensate for index
error. See INDEX CORRECTION*.
INDEX ERROR – A constant instrumental error due to the displacement of the zero or index mark or vernier of an
instrument or scale.
INDEX MAP – 1) A map showing location of collections of data which may be other maps, photos, statistical tables
or descriptions. 2) A small scale map showing locations or other information about a survey or a project. See ADMINISTRATIVE INDEX MAP, CONTROL INDEX MAP, PHOTOCONTROL INDEX MAP, PHOTOGRAPHY INDEX MAP and SALES INDEX MAP.
INDEX OF REFRACTION – A ratio between the speed of light waves in a medium as compared to the speed in a vacuum.
INDICATED CORNER – A term adopted by the U.S. Geological Survey to designate corner of the public-land surveys whose location cannot be verified by the criteria necessary to class it as a found or existent corner, but which accepted locally as the correct corner and whose location is perpetuated by such marks as fence-line intersections, piles of rock, and stakes or pipe driven into the ground, which have been recovered by field investigation.  See OBLITERATED CORNER*.
INDIRECT MEASUREMENT – Any quantitative result determined from its relation to some measurement. A stadia distance, for example, is an indirect measurement.
INDIRECT PHOTOGRAPHY – Photography in which the camera records an image display (television, radar, and so forth).
INERTIAL GUIDANCE – A system for an indirect method of measurement which converts individual accelerations and elapsed time into velocity thence into distance traveled by the measuring system.
INFRARED (IR) – That portion of the electromagnetic spectrum bounded by visible light and by microwave radiation (generally from 0.70 microns to 1000 microns).
INFRARED FILM – Photographic film sensitized to record invisible rays beyond the red end of the light spectrum.
It is also sensitive to blue and ultraviolet light and must by used with a red filter to screen out the latter.

INFRARED IMAGERY – A recording in graphic form of radiated electromagnetic energy in the heat (infrared) range of the spectrum.
INFRARED PHOTOGRAPHY – Commonly used term for imagery which is the product of direct-recording
camera/infrared film equipment. See FALSE COLOR.
INFRARED RADIATION – Electromagnetic radiation lying in the wavelength interval from about .70 microns to an indefinite upper boundary sometimes arbitrarily set at 1000 microns (0.01 centimeter). At the lower limit of this interval, the infrared radiation spectrum is bounded by visible radiation, whereas on its upper limit it is bounded by microwave radiation of the type important in radar technology.

See ELECTROMAGNETIC SPECTRUM.

INFRARED SCANNER – Instrument for obtaining thermal infrared imagery through line scanning techniques. See INFRARED THERMAL SENSING.
INFRARED THERMAL SENSING – Line scanning techniques using infrared scanners with detectors. Usually, the imagery is obtained from selected portions of the 3 to 14 micron region of the spectrum.
INLET – A narrow body of water extending into the land from a larger body of water.
INSTRUMENTAL ERROR – An error arising from imperfect condition of the instrument used. Such an error is usually systematic, but may be accidental or random.
INSTRUMENT STATION – A survey point at which a surveying instrument is set up for making measurements.
INSULAR SHELF – The subaqueous part of an island or archipelago extending from the shore outward beneath the
shallow seas to a insular talus where the bottom slopes down rapidly to the ocean depths.
INSULAR TALUS – The steep slope from the lower edge on an insular shelf into the ocean depths. It is
characterized by a marked change in gradient and usually begins at a depth of approximately 100 fathoms.
INTERFEROMETER – An apparatus used to produce and measure interference from two or more coherent wave
trains from the same source. Interferometers are used to measure wavelengths, to measure angular width of
sources, to determine the angular position of sources (as in satellite tracking), and for many other purposes.
INTERIM REVISION (USGS) – A type of limited revision which changes to a published map are determined by
reference to current aerial photographs. Obsolete data are removed from the original drawings (but contours are
not corrected), and all new data are combined on a single plate and overprinted in purple. The revised data is not
field checked. See MAP REVISION.
INTERIOR ANGLE – An angle between adjacent sides of a closed figure, measured on the inside of the figure.
INTERIOR NODE – See NODAL POINTS.
INTERIOR ORIENTATION – The adjustment of a photograph to a position within a photogrammetric system so
that the reconstructed cone of rays is geometrically identical with the cone of rays that entered the camera at exposure.
INTERIOR PERSPECTIVE CENTER – See NODAL POINTS.
INTERMEDIATE BENCH MARK – See BENCH MARK, NONMONUMENTED.
INTERMEDIATE CONTOUR – A contour line drawn between index contours.
INTEROCULAR DISTANCE – See INTERPUPILLARY DISTANCE.
INTERPOLATION – Determination of an intermediate value between fixed or tabulated values from some known
or assumed rate or system of change.
INTERPRETATION – The determination of the nature and significance on a qualitative basis of images on aerial photographs and on photographic recordings of other airborne sensors.

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INTERPRETER – 1) A person who examines and interprets aerial photographs and other imagery to obtain desired information. 2) A person who deduces the geologic significance of geophysical data.
INTERPUPILLARY DISTANCE – The distance between the pupils of the eyes of an individual.
INTERSECTION – 1) The procedure of determining the horizontal position of an unoccupied point (intersection
station) by direction observations from two or more known positions. 2) The procedure of determining the
horizontal position of a point by intersecting lines of direction obtained photogrammetrically. The lines of
direction may be obtained directly from vertical photographs or by graphic or mathematical analysis of the
photographs. 3) The general area where two or more highways join or cross, within which are included the
roadway and roadside facilities for traffic movements in that area. See INTERSECTION*.
INTERSECTION STATION – A survey point whose position is determined by directions observed from two or
more known stations. See NO CHECK POSITION.
INTERVALOMETER – A timing device for automatically operating the shutter of a camera at specified intervals.
INVAR – An alloy of nickel and steel having a very low coefficient of thermal expansion.
INVERSE COMPUTATION – The computation of the length and azimuths of a line from the coordinates of its
end points.

INVERT – The floor, bottom, or lowest part of the internal cross section of a conduit; the flowline.
INVERTED IMAGE – An image which is in reverse order, left to right, as well as from top to bottom.
ISLAND – A body of land extending above and completely surrounded by water at mean high water.
ISLAND SHELF – The zone around an island or island group, extending from the low-water line to the depths at
which there is a marked increase of slope to greater depths. Conventionally its edge is taken at 100 fathoms (or
200 meters).
ISLAND SLOPE – The steep slope from the outer edge of an island shelf into great depths.
ISOBAR – A line, generally shown on a weather map, joining points on the earth’s surface having equal barometric pressure (reduced to sea level) at a given time.
ISOBATH – Line on a marine map or chart joining points of equal depth usually in fathoms below mean sea level.
ISOCENTER – The point on a photograph intersected by the bisector of the angle of tilt which is midway between
the plumbline and the photograph perpendicular and through the principal point.
ISODIFF – One of a series of lines on a map or chart connecting points of equal correction or difference in datum,
especially useful in readjustment of surveys from one datum to another. See ISOLAT and ISOLONG.
ISOGONIC CHART – A chart showing isogonic lines properly labeled with their magnetic declinations. Lines of equal annual change in the declinations are also generally shown.
ISOGONIC LINE – A line joining points on the earth’s surface having equal magnetic declination as of a given date.
ISOLAT – An isodiff connecting points of equal latitude correction.
ISOLINE (USGS) – A line of common scale at the intersection of the planes of two overlapping aerial photographs having common perspective center and equal principal distances, applied generally in Geological Survey to the line of intersection between two components of a set of convergent photographs or the intersection of either wing component with the nominal vertical of trimetrogon photography. In the latter case the isoline becomes an isometric parallel when the nominal vertical is truly vertical.

ISOLONG – An isodiff connecting points of equal longitude correction.
ISOMETRIC PARALLEL – The intersecting line between the plane of a tilted photograph and a horizontal plane
having an equal perpendicular distance from the same perspective center. A line parallel to the horizon through
the isocenter.
ISTHMUS – A narrow strip of land, bordered on both sided by water, that connects two larger bodies of land.

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