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Military

Glossary

 

perspective to

 

angle(s)

°

 

degree(s)

a

 

azimuth of line

α

 

angle

κ

 

correction for the earth's curvature

 

sum

 

minute(s)

 

second(s)

Δ

 

delta

ΔE

 

delta easting

ΔN

 

delta northing

φ

 

latitude

Φ

 

phi

h1

 

elevation of the occupied station

λ

 

longitude

θ

 

Theta

ρ

 

symbol for rho - radius of curvature

s

 

grid distance

σ

 

sigma

τ

 

tau

ζ

 

mean observed zenith distance

1D

 

one dimensional

1DRMS

 

1-deviation root-mean-square

1LT

 

first lieutenant

1SG

 

first sergeant

2D

 

two dimensional

2DRMS

 

2-deviation root-mean-square

3D

 

three dimensional

3DRMS

 

3-deviation root-mean-square

 

 

 

A/M

 

angle measure

AAF

 

Army airfield

AAL

 

additional authorizations list

AC

 

alternating current

accuracy

 

the degree of conformity with a standard or the degree of perfection attained in a measurement; accuracy relates to the quality of a result and is distinguished from precision, which relates to the quality of the operation used to obtain the result

actual error

 

the difference between the accepted value and the measured value of a physical quantity

ADA

 

air-defense artillery

adj

 

adjusted

adjust

 

adjustment

adjusted position

 

an adjusted value for the horizontal or vertical position of a survey station, in which discrepancies due to errors in the observed data are removed, that forms a coordinated and correlated system of stations

AE

 

allowable error

AEC

 

angular error of closure

aeronautical beacon

 

a visual NAVAID displaying flashes of white and/or colored light to indicate the location of an airport, a heliport, a landmark, a certain point of a federal airway in mountainous terrain, or an obstruction

AG

 

Adjutant General

AH

 

ampere-hour

air-navigation facility

 

any facility used in, available for use in, or designed for use in the aid of air navigation (this includes landing areas; lights; any apparatus or equipment used for disseminating weather information, signaling, radio-directional finding, or radio or other electrical communication; and any other structure or mechanism having a similar purpose of guiding or controlling the flight, the landing, or the takeoff of aircraft)

airport elevation

 

the highest point of an airport's usable runways measured in feet from the MSL

airport lighting

 

various lighting aids installed on airports. These aids can include 1) airport rotating beacons—a visual NAVAID that is operated at many airports. At civil airports, alternate white and green flashes indicate the location of the airport. At military airfields, the beacon is differentiated by dual peak (two quick) white flashes between the green flashes;

2) approach-light systems (ALSs)—an airport lighting facility which provides visual guidance to landing aircraft by radiating light beams in a directional pattern by which the pilot aligns the aircraft with the extended runway centerline on his final approach for landing. A number of ALS configurations exist, both with and without sequenced flashing lights. One system, the omnidirectional ALS (ODALS), consists of seven omnidirectional flashing lights located in the approach area of a nonprecision approach. Five of the lights are located on the extended runway centerline and the other two lights are located one on each side of the runway threshold; 

3) REILs—two synchronized flashing lights, one on each side of the runway threshold, provide rapid and positive identification of the approach end of a runway;

4) visual-approach slope indicators (VASI)—an airport lighting facility providing vertical visual-approach slope guidance to aircraft during the approach for landing by radiating a directional pattern of high-intensity, red and white, focused light beams, which indicate to the pilot if he is above, below, or on the glide path. The term VASI also has a generic connotation for a tricolor-approach slope indicator consisting of a single light unit projecting a three-color, visual-approach path into the final approach area of the runway served by the system;

5) pulse-light approach-slope indicators (PLASI)—a VASI, normally consisting of a single light unit projecting a pulsating two-color, visual-approach path into the final approach area of the runway served by the system; and

6) precision approach-path indicators (PAPI)—a VASI, consisting of a single row of two or four light units, usually installed on the left side of the runway served by the system

airport reference point

 

the position of the approximate center of mass of all usable runways. This point is not strictly the center of mass of runways, since the runway width, thickness, or material is not considered in the computation. An ARP is not monumented; therefore, it is not recoverable on the ground

airport surveillance radar

 

approach control radar that is used to detect and display an aircraft's position in the terminal area. The ASR provides range and azimuth information but does not provide elevation data (coverage of the ASR can extend up to 60 nautical miles)

air-route surveillance radar

 

air-route traffic control center (ARTCC) radar used primarily to detect and display an aircraft's position while en route between terminal areas (coverage of the ARSR can extend up to 200 nautical miles)

AISI

 

automated integrated survey instrument

ALP

 

airport location point

ALS

 

approach-light system

altimeter

 

an aneroid barometer that is used for the measurement of approximate elevations or approximate differences of elevation

altitude

 

the vertical angle that is measured between the plane of the observer's true horizon and a line to the object

ambiguity resolution

 

with carrier-phase observations, the number of carrier-phase cycles between the receiver and the satellite is generally unknown and is referred to as the ambiguity and is an integer number. Single and double differences are also affected by ambiguities, which are formed by a linear combination of carrier-phase integer ambiguities (for example, a single or double differenced ambiguity). Where the integer ambiguities are unknown, they may be estimated by processing software. In some cases, these real-valued estimates may be used to determine the correct integer values, which are then held fixed. A float solution is derived when the real-valued estimates are used, rather than the integers

ang

 

angle

ant

 

antenna

AO

 

area of operation

AOC

 

airport obstruction chart

AP

 

airport plan

APFT

 

Army physical fitness test

approx

 

approximate

Apr

 

April

apron

 

a defined area on an airport or heliport intended to accommodate aircraft for purposes of loading and unloading passengers or cargo, refueling, parking, or maintenance (seaplanes use a ramp for access from the water to the apron)

AR

 

Army regulation

ARP

 

airport reference point

ARSR

 

air-route surveillance radar

ARTCC

 

air-route traffic control center

ARTEP

 

Army Training and Evaluation Program

AS

 

antispoofing

ASCII

 

American Standard Code for Information Interchange

ASPRS

 

American Society of Photogrammetry and Remote Sensing

ASR

 

airport surveillance radar

astronomical latitude

 

the angle between the plumb line and the plane of the celestial equator; also defined as the angle between the plane of the horizon and the axis of rotation of the earth. Astronomical latitude applies only to positions on the earth and is reckoned from the astronomic equator (0°), north and south through 90°. Astronomical latitude results directly from observations of celestial bodies, which are uncorrected for deflection of the vertical

astronomical longitude

 

the angle between the plane of the celestial meridian and the plane of an initial meridian that is arbitrarily chosen. Astronomical longitude results directly from observations on celestial bodies, uncorrected for deflection of the vertical

ATC

 

air traffic control

Aug

 

August

az

 

azimuth

azimuth

 

the direction of one object from another, usually expressed as an angle in degrees relative to true north (azimuths are usually measured in the clockwise direction, thus an azimuth of 90° indicates that the second object is due east of the first)

azimuth mark

 

the azimuth to a marked point or adjacent station that is visible from an occupied station, which is determined for use in dependent surveys

 

 

 

b

 

backward

backsight

 

in traversing, a backsight is a sight on a previously established traverse or triangulation station, which is not the closing sight on the traverse; in leveling, a backsight is a reading on a rod that is held on a point whose elevation has been previously determined and is not the closing sight of a level line

BAQ

 

basic allowance for quarters

base network

 

a small network of geometric figures that is used to expand from a baseline to a line of the main scheme of a triangulation network

baseline

 

a surveyed line that is established with more than usual care, to which surveys are referred for coordination and correlation; in GPS baseline reduction, geodetic parameters are estimated at one station relative to another, with the receivers at both sites observing common satellites simultaneously

basic control

 

horizontal and vertical control of third- or higher-order accuracy (determined in the field and permanently marked or monumented) that is required to control further surveys

BC

 

basic control

BCM

 

basic-control marker

bearing

 

the direction of one object from another, usually expressed as an angle in degrees relative to a specific primary direction (bearings differ from azimuths in that bearing values do not exceed 90°)

benchmark

 

a relatively permanent object, natural or artificial, bearing a marked point whose elevation above or below an adopted datum is known; usually designated as a BM, such a mark is sometimes further qualified as a PBM or as a temporary BM (TBM)

BEQ

 

bachelor enlisted quarters

bde

 

brigade

BDE

 

backward difference in elevation

BII

 

basic issue items

blast pad

 

a specially prepared surface that is placed adjacent to the ends of runways to eliminate the erosive effect of the high wind forces produced by airplanes at the beginning of their takeoff rolls

BM

 

benchmark

bn

 

battalion

broadcast ephemeris

 

the predicted satellite position in its orbit as a function of time computed from the ephemeris parameters contained in the navigation message broadcast on both the L1 and L2 carrier waves

bs

 

backsight

btry

 

battery

 

 

 

C2

 

command and control

C

 

Celsius

C/A-code

 

coarse-acquisition code

CAD

 

computer-aided design

cadastral survey

 

a survey relating to land boundaries and subdivisions, which is made to create units suitable for the transfer of or to define the limitations of a title; surveys of the public lands of the US, including retracement surveys for the identification of and resurveys for the restoration of property lines; and for corresponding surveys outside the public lands, although such surveys are usually termed land surveys

CADD

 

computer-aided design and drafting

carrier phase

 

the phase (as measured at the antenna phase center of a GPS receiver) of two sinusoidal radio signals (the two carriers) that are continuously emitted by each GPS satellite

C-check

 

collimation test for leveling

CDC

 

consecutive Doppler counts

celestial equator

 

a great circle on the celestial sphere on which any point is equidistant from the celestial poles (the plane of the earth's equator, if extended, would coincide with that of the celestial equator)

celestial meridian

 

a vertical circle (the plane of which is perpendicular to the celestial equator) passing through both celestial poles

celestial pole

 

a reference point located at the point of intersection of an indefinite extension of the earth's axis of rotation and the apparent celestial sphere

celestial sphere

 

an imaginary sphere of infinite radius, with the earth as the center, that rotates from east to west on a prolongation of the earth's axis

central meridian

 

the longitude of the horizontal center of a coordinate system (this longitude value is often the longitude origin of the coordinate system); in the case of the transverse Mercator projection, the CM is the great circle/geodesic at which the projection surface (the cylinder) touches or is tangent to the earth

CEOI

 

communications-electronics operation instructions

CEP

 

circular error probable

CESI

 

communications-electronics standing instruction

C-factor

 

collimation error; error of the sighting of the level

chron

 

chronometer

chronometer

 

a portable timekeeper with compensated balance, which is capable of showing time with extreme precision and accuracy

CID

 

continuously integrated Doppler

circle position

 

a prescribed setting (reading) of the horizontal circle of a direction theodolite, which is used for observing the initial station of a series of stations

circuit closure

 

in leveling, it is the amount by which the algebraic sum of the measured differences of elevation around a circuit fails to equal zero

circumpolar star

 

a star in any given latitude that never goes below the horizon; hence, its polar distance must be less than the given latitude; in astronomy, only those stars with a polar distance of less than 10° are considered in practical problems

cl

 

closure

C/L

 

centerline

clearway

 

an area beyond the takeoff runway that is under the control of airport authorities where terrain or fixed obstacles may not extend above specified limits (these areas may be required for turbine-powered operations and the size and upward slope of the clearway will differ depending on when the aircraft was certified)

cm

 

centimeter(s)

CM

 

central meridian

COEI

 

components of end item

collimation

 

the line of sight or aiming line of an instrument when coincident with the physical alignment of the instrument; thus, a collimation error is the angle between the line of collimation (line of sight) of a telescope and the collimation axis of the instrument

comm

 

communication

comp

 

computer

compass locator

 

a low-power, low- or medium-frequency (L/MF) NDB that is installed at the site of the outer or middle marker (MM) of an ILS (it can be used for navigation at distances of about 15 miles or as authorized in the approach procedure)

control

 

the coordinated and correlated dimensional data, which are used in geodesy and cartography to determine the positions and elevations of points on the earth's surface or on a cartographic representation of that surface; a collective term for a system of marks or objects on the earth or on a map or a photograph whose positions or elevations, or both, have been or will be determined

control survey

 

a survey that provides positions (horizontal or vertical) of points to which supplementary surveys are adjusted

CONUS

 

continental United States

coordinate system

 

an exact definition of a system of mathematics and geodetic constants that defines how a specific geographic location is converted to a set of two or three numbers (for example, an X- and Y-value [and possibly a Z-value]); in the cartographic context, most coordinate systems are Cartesian (the axes are orthogonal [perpendicular to each other]) and the units are the same on all axes; the principle exception to this is the spherical coordinate system of latitudes and longitudes

coordinates

 

linear and/or angular quantities, which designate the position of a point in relation to a given reference frame; there are two general divisions of coordinates used in surveying—polar and rectangular; these may be further subdivided into three classes—plane coordinates, spherical coordinates, and space coordinates

coords

 

coordinates

Corps Conversion

 

a software program that converts horizontal coordinates to and from geographic, state-plane, and UTM systems on the NAD 27 and the NAD 83 and converts vertical coordinates on the NGVD 29 and the NAVD 88

Corpscon

 

Corps Conversion

corr

 

correction

CORS

 

continuously operating reference station

cos

 

cosine

CPT

 

captain

C&R

 

curvature and refraction

CTT

 

common training task

cycle slips

 

cycle slips occur when there are breaks in the continuity of signal in a satellite-receiver pair. Data sampling requires the choosing of the sampling rate and the starting and finishing epochs for the observations. Data editing is required for cycle slips and for data sampling

 

 

 

D

 

ratio of side/sine

DA

 

Department of the Army

datum

 

the combination of an ellipsoid, that specifies the size and shape of the earth, and a base point from which the latitude and longitude of all other points are referenced. Before satellites, lasers, and computers, establishing precise values for these points was impossible. More recently, many datums have been established and substantial amounts of data collected based on each. Data based on one datum will not necessarily overlay data based on another datum. A geodetic datum is a reference surface consisting of five quantities: the latitude and longitude of an initial point, the azimuth and distance of a line from this point, and the parameters of the reference ellipsoid. It forms the basis for the computation of horizontal-control surveys in which the curvature of the earth is considered. A leveling datum is a level surface to which elevations are referred (usually, but not always, the MSL)

DD

 

Department of Defense

dE

 

difference in easting

DE

 

difference in elevation

declination

 

in a system of polar or spherical coordinates, the angle at the origin between a line to a point and the equatorial plane, measured in a plane perpendicular to the equatorial plane; the arc between the equator and the point measured on a great circle, which is perpendicular to the equator; as it relates to astronomy, the angular distance to a body on the celestial sphere that is measured north or south through 90° from the celestial equator along the hour circle of the body. Comparable to latitude on the terrestrial sphere and often used as a shortened term for magnetic declination

deflection of the vertical

 

the angular difference, at any place, between the upward direction of a plumb line (the vertical) and the perpendicular (the normal) to the reference spheroid. This difference seldom exceeds 30 seconds and is often expressed in two components—meridian and prime vertical

deg

 

degree(s)

det

 

detachment

dev

 

deviation

DGPS

 

differential global-positioning system

dH

 

difference in the horizontal aim

diff

 

difference

differencing

 

nondifferencing (one-way phase) is the measured carrier phase between one satellite and one receiver. Single differencing (first difference) is the difference between one-way measurements recorded at two receivers (for example, two receivers simultaneously observing a common satellite and differencing the recorded measurements). Double differencing (second difference) is the difference between two single differences (for example, two stations observing two satellites, forming differences between the site pair and the satellite pair). Triple differencing (double difference rate/epoch differences) is the differencing of double differences between consecutive epochs

dir

 

direction

direct leveling

 

the determination of DEs by the means of a continuous series of short horizontal lines. Vertical distances from these lines to adjacent ground marks are determined by direct observations on graduated rods with a leveling instrument equipped with a spirit level

direct reading

 

the reading of the horizontal or vertical circle of a theodolite or engineer transit with the telescope in the direct position. In field notes, a direct reading is indicated with a letter D preceding the observed value

direction finder

 

a radio receiver equipped with a directional sensing antenna used to take bearings on a radio transmitter

direction instrument theodolite

 

a theodolite in which the graduated horizontal circle remains freed during a series of observations. The telescope is pointed on a number of signals or objects in succession and the direction of each is read on the circle (usually by means of micrometer microscopes). Direction instrument theodolites are used almost exclusively in first- and second-order triangulation

dist

 

distance

distance angle

 

an angle in a triangle that is opposite the side which is used as a base in the solution of the triangle or a side whose length is to be computed

distance measuring equipment

 

equipment that is (airborne or ground) used to measure (in nautical miles) the slant-range distance of an aircraft from the DME NAVAID

DIVARTY

 

division artillery

DMA

 

Defense Mapping Agency

DME

 

distance measuring equipment

DMS

 

Defense Mapping School

dN

 

difference in northing

DOD

 

Department of Defense

DOP

 

dilution of precision

DPW

 

Directorate of Public Works

D/R

 

direct/reverse

DRU

 

data recording unit

dsplcd

 

displaced

DT

 

displaced threshold

dV

 

difference in the vertical aim

 

 

 

E

 

east

EAC

 

echelons above corps

EC

 

error of closure

ECEF

 

earth centered earth fixed

ecliptic

 

the great circle of the celestial sphere that is the apparent path of the sun among the stars or of the earth as seen from the sun. It is inclined to the celestial equator at an angle of about 23°27′

EDM

 

electronic distance measurement

EDME

 

electronic distance measuring equipment

Ee

 

error in easting

elev

 

elevation

elevation

 

the vertical distance from a datum, usually the MSL, to a point or object on the earth's surface (not to be confused with altitude, which refers to points or objects above the earth's surface)

ell

 

ellipsoidal

ellipsoid

 

the mathematical shape that best describes the shape of the earth and yet is relatively simple to deal with mathematically. Ellipsoids are defined with two numbers. First, the equatorial radius is specified (also referred to as the semimajor axis). Second, one of the following three numbers is given, the polar radius (also known as the semiminor axis), the eccentricity, or the flattening. Given the equatorial radius and any one of the three secondary values, the remaining secondary values can be computed. A specific determination of the size of the earth is often referred to as an ellipsoid. For example, the phrase "Clarke ellipsoid of 1866" is frequently used to refer to the measurements of the size of the earth made by Clarke in 1866

ellipsoid height

 

the height of an object above the reference ellipsoid in use. This term is generally used to qualify an elevation as being measured from the ellipsoid as opposed to the geoid. GPS systems calculate ellipsoidal height. The geoid height at that location must be subtracted to obtain what is commonly referred to as the elevation

elongation

 

the point in the apparent movement of a circumpolar star when the star reaches the extreme position east or west of the meridian

EM

 

engineer manual

en

 

engineer

En

 

error in northing

eng

 

engineer

engr

 

engineer

EOR

 

end of runway

ephemeris time

 

a uniform measure of time that is defined by the laws of dynamics and determined in principle from the orbital motions of the planets, specifically in the orbital motion of the earth

equation of time

 

the algebraic difference in hour angle between apparent solar time and mean solar time (usually labeled plus or minus), as it is to be applied to mean solar time to obtain apparent solar time

equinox

 

one of the two points of intersection of the ecliptic and the celestial equator, which is occupied by the sun when its declination is 0°

error

 

the difference between an observed and true value; a class of small inaccuracies due to imperfections in equipment or techniques, surrounding conditions, or human limitations; not to be confused with blunders or mistakes

error of closure

 

the amount by which a quantity obtained by a series of related measurements differs from the true or fixed value of the same quantity. These include errors of closure for the following:

Angle. The amount by which the actual sum of a series of angles fails to equal the theoretically exact value of that sum.

Azimuth. The amount by which two values of the azimuth of a line, derived by different surveys or along different routes, fail to be exactly equal to each other.

Horizon. The amount by which the sum of a series of adjacent measured horizontal angles around a point fails to equal exactly 360°. Measurement of the last angle of the series is called closing the horizon (sometimes called closure of horizon).

Leveling. The amount by which two values of the elevation of the same BM, derived by different surveys or through different survey routes or by independent observations, fail to be exactly equal to each other.

Loop. The error in the closure of a survey on itself.

 

Triangle. The amount by which the sum of the three observed angles of a triangle fails to equal exactly 180° plus the spherical excess of the triangle.

Traverse. The amount by which a value of the position of a traverse station, as obtained by computation through a traverse, fails to agree with another value of the same station as determined by a different set of observations or routes of survey

esc

 

escape

 

 

 

f

 

forward

F

 

Fahrenheit

FA

 

field artillery

FAA

 

Federal Aviation Administration

FAA 405

 

Federal Aviation Administration Publication 405

FAO

 

finance and accounting office

FAR

 

Federal Aviation Regulation

FAR-77

 

Federal Aviation Regulation, Part 77

FDE

 

forward difference in elevation

Feb

 

February

FEBA

 

forward edge of the battle area

FED

 

Facilities Engineering Division

FGCC

 

Federal Geodetic Control Committee

FGCS

 

Federal Geodetic Control Subcommittee

final-approach course

 

a straight-line extension of a localizer, a final approach radial/bearing, or a runway centerline, all without regard to distance

fixed elevation

 

an elevation that has been adopted (either as a result of tide observations or previous adjustment of spirit leveling) and is held at its accepted value in any subsequent adjustment

FM

 

field manual

FM

 

frequency modulated

FO

 

forward observer

foresight

 

an observation of the distance and direction to the next instrument station. In traversing, a foresite is a point set ahead to be used for reference when resetting the transit or line or when verifying the alignment. In leveling, a foresite is the reading on a rod that is held at a point whose elevation is to be determined

FOUO

 

for official use only

FRAGO

 

fragmentary order

frequency

 

the number of complete cycles per second existing in any form of wave motion

FRNP

 

Federal Radio Navigation Plan

fs

 

foresight

FS

 

fire support

FSCOORD

 

fire-support coordinator

ft

 

feet, foot

 

 

 

G2

 

Assistant Chief of Staff, G2 (Intelligence)

G3

 

Assistant Chief of Staff, G3 (Operations and Plans)

GCA

 

ground-controlled approach

GDOP

 

geometric dilution of precision

geod

 

geodetic

geodesy

 

a branch of applied mathematics concerned with the determination of the size and shape of the earth (geoid). Direct measurements (triangulation, leveling, and gravimetric observations) determine the exact location of points on the earth's surface and its external gravitational field

geodetic control

 

a system of horizontal and/or vertical control stations that have been established and adjusted by geodetic methods and in which the shape and size of the earth (geoid) have been considered in position computations

geodetic latitude

 

the angle at which the normal (at a point on the reference spheroid) forms with the plane of the geodetic equator. Geodetic latitudes are reckoned from the equator, but in the horizontal-control survey of the US, they are computed from the latitude of station Meades Ranch as prescribed in NAD 27

geodetic leveling

 

spirit leveling of a high order of accuracy, usually extended over large areas, to furnish accurate vertical control as a basis for the control in the vertical dimension for all surveying and mapping operations

geodetic longitude

 

the angle between the plane of the geodetic meridian and the plane of an initial meridian. A geodetic longitude can be measured by the angle at the pole of rotation of the reference spheroid between the local and initial meridians or by the arc of the geodetic equator intercepted by those meridians. In the US, geodetic longitudes are numbered from the meridian of Greenwich, but are computed from the meridian of station Meades Ranch as prescribed in NAD 27. A geodetic longitude differs from the corresponding astronomical longitude by the amount of the prime vertical component of the local deflection of the vertical divided by the cosine of the latitude

geodetic reference system

 

the technical name for a datum. The combination of an ellipsoid, which specifies the size and shape of the earth, and a base point from which the latitude and longitude of all other points are referenced

geodetic survey

 

a survey of a large land area in which corrections are made for the curvature of the earth's surface

geographic coordinates

 

an inclusive term that is generally used to designate both geodetic and astronomical coordinates

geoid

 

the surface within or around the earth that is everywhere normal to the direction of gravity and coincides with MSL in the oceans

GEOID93

 

Geoid reference model 1993

GEOID96

 

Geoid reference model 1996

GEOID99

 

Geoid reference model 1999

geoid height

 

the height of the geoid above the ellipsoid in use (this usually refers to the height of the geoid above the WGS-84 ellipsoid upon which GPS is based)

GEOREF

 

geographic reference

GIS

 

geographic information system

global positioning system

 

a system (developed by the US military) based on satellites and sophisticated receivers that are capable of accurately measuring the geodetic location of a receiver at any place in the world and is widely used in surveying and navigational situations

GPS

 

global positioning system

GPS-S

 

global positioning system-survey

gravimeter

 

a weighing device or instrument of sufficient sensitivity that is used to register variations in the weight of a constant mass when the mass is moved from place to place on the earth and thereby is subjected to the influence of gravity at those places

gravitation

 

the acceleration produced by the mutual attraction of two masses, directed along the line joining their centers of mass, and of magnitude inversely proportional to the square of the distance between the two centers of mass

gravity

 

viewed from a frame of reference freed in the earth (acceleration imparted by the earth to a mass), which is rotating the earth. Since the earth is rotating, the acceleration observed as gravity is the resultant of the acceleration of gravitation and the centrifugal acceleration arising from this rotation and the use of an earthbound rotating frame of reference.

ground-controlled approach

 

a radar approach system operated from the ground by ATC personnel transmitting instructions to the pilot by radio (the approach may be conducted with ASR and/or PAR)

GRS

 

geodetic reference system

GRS 80

 

Geodetic Reference System of 1980

GS

 

general support

GSI

 

glide-slope indicator

GSR

 

ground-surveillance radar

GySgt

 

gunnery sergeant

 

 

 

h

 

ellipsoidal height

h

 

hour(s)

H

 

orthometric height

HARN

 

high-accuracy reference network

H Dist

 

horizontal distance

HDOP

 

horizontal dilution of precision

height of instrument

 

in spirit leveling, it is the height of the line of sight of a leveling instrument above the adopted datum. In stadia surveying, it is the height of the center of the telescope (horizontal axis) of the transit or telescopic alidade above the ground or station mark. In trigonometric leveling, it is the height of the center of the theodolite (horizontal axis) above the ground or station mark

Hg

 

the symbol for the element mercury

HHB

 

headquarters and headquarters battery

HHC

 

headquarters and headquarters company

HI

 

height of instrument

horizontal control

 

a control point that determines horizontal positions only, with respect to parallels and meridians or to other lines of reference

horizontal refraction

 

a natural error in surveying, which is the result of the horizontal bending of light rays between a target and an observing instrument. This error is usually caused by the differences in density of the air along the path of the light rays, resulting from temperature variations

HQ

 

headquarters

ht

 

height

HT

 

height of the observed target

 

 

 

IEW

 

intelligence and electronic warfare

IFR

 

instrument flight rules

IID

 

intermittently integrated Doppler

ILS

 

instrument landing system

IM

 

inner marker

imaginary surface

 

any surface that is defined in FAR-77, subpart C. A specified surface is an imaginary surface (other than a supplemental surface) that is designated by appropriate FAA authorities for defining obstructions. This surface may or may not be the surface specified in FAR-77 for existing approach minimums. A supplemental surface is an imaginary surface designated by appropriate FAA authorities. A supplemental surface will normally lie below a specified surface and is intended to provide additional obstruction information. An object that penetrates a supplemental surface only is a supplemental obstruction

in

 

inch(es)

INS

 

inertial navigation system

inst

 

instrument

instr

 

instrument

instrument landing system

 

a precision instrument approach system that normally consists of electronic components and visual aids (for example, localizer, glide slope, outer marker (OM), MM, and approach lights)

instrument runway

 

a runway equipped with electronic and visual NAVAIDs

int

 

initials

intersection method

 

a method of determining the horizontal position of a point by observations from two or more points of known position, thus measuring directions that intersect at the station being located. A station whose horizontal position is located by intersection is known as an intersection station

ionospheric correction

 

the ionosphere causes a delay in the propagation of a GPS signal that can be estimated with 50 percent accuracy using any recognized atmospheric model. On baselines shorter than 20 kilometers, it is mostly eliminated by relative positioning. For greater accuracy, it can be mostly eliminated by dual frequency observations and processing

isogonic chart

 

a chart that features a system of isogonic lines, each for a different value of the magnetic declination

isogonic line

 

a line drawn on a map or chart joining points of equal magnetic variation

ISVT

 

initial site-visitation trip

 

 

 

JAG

 

Judge Advocate General

Jan

 

January

 

 

 

K

 

a scale factor used to convert a measured distance to a grid distance

K

 

a scale factor used to reduce a grid distance

KE

 

correction to easting

km

 

kilometer(s)

KN

 

correction to northing

 

 

 

landing direction indicator

 

a device that visually indicates the direction in which landings and takeoffs should be made

lat

 

latitude

latitude

 

the north/south component of the spherical coordinate system most widely used to record geodetic locations. Originally, when the earth was thought to be spherical, a degree of latitude represented one degree of arc on the surface of the earth, which is referenced to the center of the earth. Now that it is known that the earth is ellipsoidal in shape, there are several types of latitude. The usual definition of latitude is the angle a line, perpendicular to the surface of the ellipsoid, forms with the plane of the equator. This is also referred to as the geographic latitude or geodetic latitude. Whenever the unqualified term latitude is used, it is generally accepted that it refers to the geographic latitude. Normal conventions dictate that north latitudes be given in degrees where positive numbers indicate north latitudes and negative numbers indicate south latitudes

L-band

 

frequency used by SVs to exchange information

LEC

 

linear error of closure

level datum

 

a level surface to which elevations are referred. The generally adopted level datum for leveling in the US is the MSL. For local surveys, an arbitrary level datum is often adopted and defined in terms of an assumed elevation for some physical BM

level net

 

Lines of spirit leveling connected together to form a system of loops or circuits extending over an area

line of sight

 

the straight line between two points (this line is in the direction of a great circle but does not follow the curvature of the earth); also, the line extending from an instrument along which distant objects are seen when viewed with a telescope or another sighting device

L/MF

 

low or medium frequency

localizer

 

the component of an ILS that provides course guidance to the runway

localizer back course

 

the course line defined by the localizer signal along the extended runway centerline in the opposite direction to the normal localizer approach course (front course)

localizer-type directional aid

 

a NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a localizer; however, it is not part of a complete ILS and is not aligned with the runway

lon

 

longitude

long

 

longitude

longitude

 

the east/west component of the spherical coordinate system most widely used to record geodetic locations. Lines of longitude are great circles/geodesics, which pass through the north and south pole, and intersect the equator. All lines of longitude proceed in a true north/south direction. The imaginary lines of longitude are assigned values that represent, in degrees of arc, the distance of the line from the prime meridian (the line of longitude that passes through Greenwich, England, is the most common prime meridian in use today)

long-range navigation

 

an electronic navigation system by which hyperbolic LOPs are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. The long-range navigation (LORAN) A operates in the 1750- to 1950- kilohertz frequency band. The LORAN C and D operate in the 100- to 110-kilohertz frequency band

LOP

 

line of position

LORAN

 

long-range navigation

LRA

 

local reproduction authorized

LTC

 

lieutenant colonel

 

 

 

m

 

meter(s)

m

 

minute(s)

MACOM

 

major Army command

mag

 

magnetic

main-scheme station

 

a station through which the basic survey computations are carried, also called a principal station

Mar

 

March

marker beacon

 

an electronic NAVAID transmitting a 75-megahertz vertical-fan or bone-shaped radiation pattern. Marker beacons are identified by their modulation frequency and keying code and, when received by compatible airborne equipment, indicate to the pilot (both aurally and visually) that he is passing over the facility. Marker beacons include the following:
Basic-control marker (BCM). When installed, this normally indicates the localizer basic-control final-approach fix where approach descent is commenced.
Inner marker (IM). A marker beacon (used with an ILS category-II precision approach) that is located between the MM and the end of the ILS runway. It also marks progress during an ILS category-III approach. The IM is usually located at the point of decision height for ILS category-II approaches.
MM. A marker beacon that defines a point along the glide slope of an ILS, usually located at or near the point of decision height for ILS category-I approaches.
OM. A marker beacon that is at or near the glide-slope intercept altitude of an ILS approach. The OM is normally located 4 to 7 miles from the runway threshold on the extended centerline of the runway

mean sea level

 

the mean surface-water level that was determined by averaging heights at all stages of the tide over a 19-year period (often used as a reference for general leveling operations)

meas

 

measurement

meridian

 

in a cartographic/geodetic context, a meridian is a line of longitude

met

 

meteorological

MET

 

missile escort team

MFR

 

memorandum for record

MGRS

 

military grid-reference system

mi

 

mile(s)

micro

 

micrometer

MID E

 

middle easting

MID N

 

middle northing

mil

 

a unit of angular measurement that is equal to 1/6400 of 360° and used especially in FA

min

 

minute(s)

minimum

 

weather condition requirements that are established for a particular operation or type of operation (for example, instrument flight rules (IFR) takeoff or landing, alternate airport for IFR flight plans, or visual flight rules (VFR) flight)

missed approach

 

a maneuver that is conducted by a pilot when an instrument approach cannot be completed to landing

MLRS

 

multiple-launch rocket system

MLS

 

microwave landing system

mm

 

millimeter(s)

MM

 

middle marker

mn

 

mean

mo

 

month

MOA

 

memorandum of agreement

Mon

 

Monday

monument

 

any object or collection of objects that indicate the position on the ground of a survey station. In military surveys, the term monument usually refers to a stone or concrete station marker containing a special bronze plate on which the exact station point is marked

MOS

 

military occupational specialty

movement area

 

the runways (exclusive of apron areas), taxiways, and other areas of an airport/heliport, which are used for taxiing, takeoff, and landing of aircraft. At airports/heliports with a tower, specific approval for entry onto the movement area must be obtained from ATC

MRSE

 

mean radial spherical error

MSL

 

mean sea level

MTP

 

mission training plan

multipath errors

 

errors caused when one or more reflected signals, interfering with the main signal because of their common time origin but different path lengths, are superimposed with their relative phase offsets on the primary signal at the receiver. Cyclic perturbations of the carrier are caused by this superimposition as the various signals undergo changes in their relative phase offsets as the geometric relation between the nearby and distant reflecting surfaces and the satellite and receiver changes

multistation reduction

 

geodetic parameters that are estimated at more than two stations using simultaneous observations

 

 

 

n

 

geoid height

N

 

north

NA

 

not applicable

NAD

 

North American Datum

NAD 27

 

North American Datum of 1927

NAD 83

 

North American Datum of 1983

nadir

 

the point of the celestial sphere that is directly opposite the zenith and vertically downward from the observer

NAS

 

National Airspace System

National Flight Data Center

 

a facility in Washington, District of Columbia, that was established by the FAA to operate a central aeronautical information service for the collection, validation, and dissemination of aeronautical data in support of the activities of the government, industry, and the aviation community. The information is published in the National Flight Data Digest (NFDD)

National Flight Data Digest

 

a daily (except weekends and Federal holidays) publication of flight information (appropriate to aeronautical charts or aeronautical publications) that provides operational flight data which is essential to safe and efficient aircraft operations

NATO

 

North Atlantic Treaty Organization

NAVAID

 

navigational aid

NAVAID survey

 

the process of determining the position and/or elevation of one or more NAVAIDs and adjunctive points on associated runways or extended runway centerlines. A NAVAID survey that is performed as part of the OC survey is called a combined NAVAID survey. A NAVAID survey that is not performed as part of a normal OC survey is called a special NAVAID survey

NAVD 88

 

North American Vertical Datum of 1988

navigable airspace

 

airspace at and above the minimum flight altitude that is prescribed in FARs, including airspace needed for safe takeoff and landing

navigational aid

 

any visual or electronic device, airborne or on the surface, which provides point-to-point guidance information or position data to aircraft in flight

NAVSTAR

 

Navigation Satellite Timing and Ranging

NBC

 

nuclear, biological, and chemical

NCAD

 

New Cumberland Army Depot

NCO

 

noncommissioned officer

NCOIC

 

noncommissioned officer in charge

NDB

 

nondirectional beacon

NE

 

northeast

NFDD

 

National Flight Data Digest

NGRS

 

National Geodetic Reference System

NGS

 

National Geodetic Survey

NGVD 29

 

National Geodetic Vertical Datum of 1929

NIMA

 

National Imagery and Mapping Agency

NL

 

notes and legends

No.

 

number

NOAA

 

National Oceanic and Atmospheric Administration

nondirectional beacon

 

an L/MF or UHF radio beacon transmitting nondirectional signals whereby the pilot of an aircraft that is equipped with direction-finding equipment can determine his bearing to or from the station. When the NDB is installed in conjunction with an ILS marker, it is normally called a compass locator

nonprecision approach procedure

 

a standard instrument-approach procedure in which no electronic glide slope is provided (for example, VOR, TACAN, NDB, localizer, ASR, and simplified directional facility [SDF] approaches)

North American Datum

 

the initial point of this datum is located at Meades Ranch, Kansas. Based on the Clarke spheroid of 1866, the geodetic positions of this system are derived from a readjustment of the triangulation of the entire country in which Laplace azimuths were introduced

Nov

 

November

NSATS

 

number of satellites

NSRS

 

National Spatial Reference System

NW

 

northwest

 

 

 

obs

 

observed

observer's meridian

 

a celestial meridian passing through the zenith (at the point of observation) and the celestial poles

obstruction

 

any object that penetrates a specified surface. An object that penetrates a supplemental surface is a supplemental obstruction. The most obstructing object in a set of objects is the one that penetrates an imaginary surface further than any other object in the set

OC

 

obstruction chart

occ

 

occupied

OCONUS

 

outside continental United States

Oct

 

October

ODALS

 

Omnidirectional Approach Light System

offset line

 

a supplementary line that is close to and roughly parallel with a main line (measured offsets). When a line for which data are desired is in such a position that it is difficult to measure over it, the required data are obtained by running an offset line in a convenient location and measuring offsets from it to salient points on the other line

OIS

 

obstruction identification surface

OM

 

outer marker

op

 

operator

open traverse

 

a survey traverse which begins from a station of known or adopted position but does not end upon such a station

OPORD

 

operation order

order of accuracy

 

a mathematical ration that defines the general accuracy of measurements made in a survey (for example, first, second, third, fourth, or lower order)

ortho

 

orthometric

orthometric height

 

another name for the elevation of an object (the height of an object above the geoid)

OTF

 

on the fly

OVM

 

organization vehicle maintenance

 

 

 

p

 

page(s)

PAC

 

Personnel and Administration Center

PACS

 

primary airport control station

PADS

 

Position and Azimuth Determination System

PAPI

 

precision approach-path indicator

PAR

 

precision approach radar

parallax

 

the apparent displacement or the difference in apparent direction of an object as seen from two different points not on a straight line with the object; also, the angular difference in direction of a celestial body as measured from two points on the earth's orbit

PBM

 

permanent benchmark

PC

 

personal computer

P-code

 

precision code

PDOP

 

positional dilution of precision

permanent benchmark

 

a BM of as nearly permanent character as it is practicable to establish. Usually designated simply as BM. A PBM is intended to maintain its elevation with reference to an adopted datum, without change, over a long period

PFC

 

private first class

pgdn

 

page down

pgs

 

pages

pgup

 

page up

picture point

 

a terrain feature that is easily identified on an aerial photograph and whose horizontal or vertical position or both have been determined by survey measurements. Picture points are marked on the aerial photographs by the surveyor and are used by the photomapper

PIR

 

precise instrument runway

PLASI

 

pulse-light approach-slope indicator

PLGR

 

precise lightweight GPS receiver

plumb line

 

the line of force in a geopotential field; the continuous curve to which the direction of gravity is everywhere tangential; or, the line indicated by a plumb-bob cord

PM

 

post meridian

PMCS

 

preventive-maintenance checks and services

POC

 

point of contact

POL

 

petroleum, oils, and lubricants

pos

 

position

POV

 

privately owned vehicle

ppm

 

part(s) per million

PPS

 

Precise Positioning Service

PRC

 

pseudorange correction

precise ephemeris

 

the precise ephemeris is the postprocessed position of a satellite in its orbit as a function of time. It is computed from data that are observed at tracking stations at fixed locations and is available from various global agencies

precision approach procedure

 

a standard instrument-approach procedure in which an electronic glide slope is provided or used (for example, ILS and PAR approaches)

precision approach radar

 

radar equipment usually located at military or joint-use airfields that detects and displays azimuth, elevation, and range of aircraft on the final approach course to a runway. The controller issues guidance to the pilot based on the aircraft's position and elevation relative to the touchdown point on the runway displayed on the radarscope

prime meridian

 

the specific meridian (for example, line of longitude) that is assigned the value of zero and to which all other meridians are referenced. While Greenwich, England, is almost universally accepted as the prime meridian, several other meridians (such as the meridian of Paris) remain in use

prime vertical

 

the vertical circle through the east and west points of the horizon. It may be true, magnetic, compass, or grid depending upon which east or west points are involved

PRN

 

pseudorandom noise

pseudorange measurement

 

a measurement obtained by comparing the time signal generated by the satellite clock to the time signal generated by the receiver clock to determine propagation time and, subsequently, the range

PVC

 

polyvinyl chloride

PX

 

post exchange

 

 

 

r

 

degrees of freedom

R1

 

reject value, use first mean value

R2

 

reject value, use second mean value

radar

 

a device for radio detection and ranging. Radar measures the time interval between transmitted and received radio pulses and provides information on the range, azimuth, and/or elevation of objects in the path of the transmitted pulse. A primary radar system uses reflected radio signals. A secondary radar system is a system wherein a radio signal that is transmitted from a radar station initiates the transmission of a radio signal from another station

radar approach

 

an instrument-approach procedure that uses PAR or ASR

RC

 

ratio of closure

RDOP

 

relative dilution of precision

REIL

 

runway end identifier light

rep

 

repetition

right ascension

 

the angular distance that is measured eastward on the equator from the vernal equinox to the hour circle through the celestial body, from 0 to 24 hours

RM

 

reference mark

RMS

 

root-mean-square

Ro

 

rejected by observation

RPP

 

runway plans and profiles

RT

 

relocated threshold

RTCM

 

Radio Technical Commission for Maritime

RTK

 

real-time kinematic

RTO

 

radio/telephone operator

runway

 

a defined rectangular area on a land airport that is prepared for the landing and takeoff run of aircraft along its length

RVR

 

runway visual range

RVV

 

runway visibility value

rwy

 

runway

 

 

 

s

 

seconds

S

 

south

S1

 

Adjutant (United States Army)

S3

 

Operations and Training Officer (United States Army)

S4

 

Supply Officer (United States Army)

S/A

 

selective availability

SACS

 

secondary airport control station

sampling interval (data rate)

 

the interval (in seconds) at which observations are logged to memory

SATO

 

Scheduled Airline Ticket Office

SC

 

special committee

SCP

 

survey control point

SDF

 

simplified directional facility

SDNCO

 

staff duty noncommissioned officer

SE

 

southeast

secs

 

seconds

Sep

 

September

SEP

 

spherical error probable

sexagesimal system

 

a system of notation by increments of 60 (the division of a circle into 360°, each degree into 60 minutes, and each minute into 60 seconds)

SFC

 

sergeant first class

SGT

 

sergeant

SIC

 

survey information center

SIF

 

stadia-interval factor

simplified directional facility

 

a NAVAID that is used for nonprecision instrument approaches. The final approach course is similar to that of an ILS localizer, except that the SDF course may not be aligned with the runway and the course may be wider, resulting in less precision

sin

 

sine

SINCGARS

 

Single-Channel Ground-to-Air Radio System

SLC

 

sea-level coefficient

SM

 

soldier's manual

software

 

GPS software is classified as data logging, postprocessing reduction, and real-time processing. Data-logging software relates to the operation of the receiver and is not field-tested. Postprocessing software should be tested using a BM data set

SOI

 

signal operation instructions

solar day

 

the interval of time from the transit of either the sun or the mean sun across a given meridian to the next successive transit of the same body across the same meridian; also, the duration of one rotation of the sun

solar time

 

time based upon the rotation of the earth relative to the sun; time on the sun

SOP

 

standing operating procedure

SPC

 

specialist

SPCE

 

survey planning and coordination element

SPCO

 

survey planning and coordinating officer

spheroid

 

any figure differing slightly from a sphere

SPHS

 

specially prepared hard surface

spirit leveling

 

spirit leveling follows the geoid and its associated level surfaces, which are irregular rather than any mathematically determined spheroid or ellipsoid and associated regular level surfaces

SPS

 

Standard Positioning Service

SSF

 

standard solution file

SSG

 

staff sergeant

SSGCN

 

Standards and Specifications for Geodetic Control Networks

SSI

 

standing signal instructions

ST

 

special text

sta

 

station

state-plane coordinate system

 

the meridian used as the axis of Y for computing projection tables for a state coordinate system (the CM of the system usually passes close to the center of the figure of the area or zone for which the tables are computed)

std

 

standard

stopway

 

an area beyond the takeoff runway that is at least as wide as the runway, is centered upon the extended runway centerline, is able to support an airplane during an aborted takeoff without causing structural damage to the airplane, and is designated by airport authorities for use in decelerating the airplane during an aborted takeoff. The location of threshold lights has no bearing on an area being designated as a stop way

STP

 

soldier training publication

sub

 

subtract

SV

 

satellite vehicle

t

 

grid azimuth

T

 

geodetic azimuths

TA

 

target acquisition

TAB

 

target-acquisition battery

TACAN

 

tactical air navigation

tactical air navigation

 

a UHF electronic rho-theta air NAVAID, which provides suitably equipped aircraft with a continuous indication of bearing and distance to the TACAN station

tan

 

tangent

target

 

any object or point toward which something is directed; also, an object which reflects a sufficient amount of a radiated signal to produce an echo signal on detection equipment

TBM

 

temporary benchmark

TCMD

 

transportation-control and movement document

TDY

 

temporary duty

TDZE

 

touchdown zone elevation

TEC

 

Topographic Engineering Center

TECHOPORD

 

technical operation order

tel

 

telescope

temp

 

temperature

TG

 

trainer's guide

thr

 

threshold

threshold

 

the beginning of that portion of the runway usable for landing. A DT is located at a point on the runway other than the designated beginning of the runway. The displaced area is available for takeoff or rollout of aircraft. The DT paint bar is entirely on the usable landing surface. A relocated threshold (RT) is located at a point on the runway other than the beginning of the full strength pavement. The area between the former threshold and the RT is not available for the landing or takeoff of aircraft. The abandoned runway area may or may not be available for taxiing

tidal benchmark

 

a BM set to reference a tide staff at a tidal station and the elevation that is determined with relation to the local tidal datum

tidal datum

 

specific tide levels, which are used as surfaces of reference for depth measurements in the sea and as a base for the determination of elevation on land. Many different datums have been used, particularly for leveling operations

TM

 

technical manual

TMP

 

transportation motor pool

TOD

 

tabulated operational data

TOE

 

table(s) of organization and equipment

topo

 

topographic

touchdown zone

 

the first 3,000 feet of the runway beginning at the threshold

touchdown zone elevation

 

the highest elevation in the touchdown zone. The OC program specifications require that the TDZE will be determined only for runways with SPHSs equal to, or greater than, 3,000 feet in length

TP

 

temporary point

TRADOC

 

United States Army Training and Doctrine Command

transit

 

the apparent passage of a star or another celestial body across a defined line of the celestial sphere, as a meridian, prime vertical, or almucantar; the apparent passage of a star or another celestial body across a line in the reticle of a telescope, or some line of sight; a theodolite with the telescope mounted so that it can be transited

transmissometer

 

an apparatus used to determine visibility by measuring the transmission of light through the atmosphere and is the measurement source for determining runway visual range (RVR) and runway visibility value (RVV)

trig list

 

an extremely or excessively precise list

tropospheric correction

 

the troposphere causes a propagation delay of a GPS signal. This delay can be estimated using any recognized atmospheric model and can be mostly eliminated by relative positioning for short lengths and modeled for longer baselines

 

 

 

UDS

 

user-defined sequence

UERE

 

user equivalent range error

UHF

 

ultrahigh frequency

universal transverse Mercator

 

a series of 120 coordinate systems that are based on the transverse Mercator projection that was originally developed by the US Army for a worldwide mapping project. Sixty zones are used to map the northern hemisphere, and the remaining zones apply to the southern hemisphere. Each zone is 6° wide and is numbered. Zone 1 covers longitudes of 180° W through 174° W. The remaining zones are numbered sequentially as they move east. All zones have their origin at the equator, use the meter as the system unit, and have a false easting of 500,000 meters and a false northing of 0. A scale reduction factor of 0.9996 is used on all zones. Zones for the southern hemisphere are identical to their northern counterpart except that the false northing is set to 10,000,000 to eliminate negative Y coordinates

UPS

 

universal polar stereographic

US

 

United States

USA

 

United States of America

USAADCENFB

 

United States Army Air Defense Center and Fort Bliss

USAASA

 

United States Army Aeronautical Services Agency

USACE

 

United States Army Corps of Engineers

USAES

 

United States Army Engineer School

USAF

 

United States Air Force

USAPA

 

United States Army Publishing Agency

USAPPC

 

United States Army Publications and Printing Command

USCG

 

United States Coast Guard

USC&GS

 

United States Coast and Geodetic Survey

USGS

 

United States Geological Survey

UTC

 

universal time, coordinated

UTM

 

universal transverse Mercator

 

 

 

VASI

 

visual-approach slope indicator

VDOP

 

vertical dilution of precision

vern

 

vernier

vernal equinox

 

that point of intersection of the ecliptic and the celestial equator, which is occupied by the sun as it changes from south to north declination on or about March 21 (same as the first of Aries, the first point of Aries, or the March equinox)

vert

 

vertical

vertical circle

 

a great circle of the celestial sphere (through the zenith and nadir) that is perpendicular to the horizon; also, a graduated disk (mounted on an instrument in such a manner that the plane of its graduated surface can be placed in a vertical plane), which is used primarily for measuring vertical angles in astronomical and geodetic work

vertical control

 

the measurements taken by surveying methods for the determination of elevation only with respect to an imaginary level surface, usually the MSL

vertical-control datum

 

any level surface (for example, the MSL) taken as a surface of reference from which to reckon elevations. Although a level surface is not a plane, the vertical-control datum is frequently referred to as the datum plane

very-high-frequency omnidirectional range

 

a VHF NAVAID, which provides suitably equipped aircraft with a continuous indication of bearing to the VOR station

very-high-frequency omnidirectional range and tactical air navigation

 

a navigational facility consisting of two components, a VOR and a TACAN, which provide VOR azimuth, TACAN azimuth, and TACAN distance

VFR

 

visual flight rules

VHF

 

very high frequency

VOR

 

very-high-frequency omnidirectional range

VORTAC

 

very-high-frequency omnidirectional range and tactical air navigation

 

 

 

W

 

west

WAAS

 

wide-area augmentation system

WDI

 

wind-direction instrument

WGS

 

World Geodetic System

WGS 72

 

World Geodetic System 1972

WGS 84

 

World Geodetic System 1984

widelaning

 

a linear combination of the measured phases of L1 and L2, based on the frequency difference. Widelane ambiguities can be resolved easier than L1 and L2 ambiguities, because the resulting 0.862-meter wavelength is much longer than the individual L1 and L2 wavelengths. Knowledge of the widelane ambiguity helps to solve the L1 ambiguity, after which a simple computation will give the L2 ambiguity

World Geodetic System 1984

 

a global datum that is based on electronic technology, which is still to some degree classified. Data on the relationship of as many as 65 different datums to WGS-84 is available to the public. As a result, WGS 84 is becoming the base datum for the processing and conversion of data from one datum to any other datum. GPS is based on this datum. The difference between WGS 84 and NAD 83 is small and is generally considered to be insignificant

 

 

 

XVIII

 

the Table 18 value extracted from DMS ST 045

X, Y, and Z

 

variables used to depict coordinates in the X, Y, and Z axis

 

 

 

Y-code

 

the military's classified, encrypted precision code

yr

 

year(s)

 

 

 

ZD

 

zenith distance

zen

 

zenith

zenith

 

the point where an infinite extension of a plumb (vertical) line, at the observer's position, pierces the celestial sphere above the observer's head

zenith distance

 

the complement of the altitude; the angular distance from the zenith of the celestial body measured along a vertical circle

 

 



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