
V


Variance

The square of the standard deviation

VDOP

VDOP = Vertical Dilution of Precision (height only)

Vector

Images defined by sets of straight lines that are defined by the locations of the endpoints. Vector graphics require much less
storage space than raster or bitmapped graphics

Velocity Made Good (VMG)

The speed you are closing in on a destination along a desired course

Very High Frequency (VHF)

Radio frequencies in the band from 30 to 300 MHz

VMG

Velocity Made Good. Marine term giving velocity to waypoint taking into effect the course you are steering

VOG

Velocity Over Ground. Same as Ground Speed



W


WAAS

Wide Area Augmentation System. A system of satellites and ground stations that provide GPS signal corrections, giving a even
better position accuracy

WADGPS

A form of DGPS in which the user's GPS receiver receives corrections determined from a network of reference stations distributed
over a wide geographical area. The corrections are typically supplied in real time by way of a geostationary communications satellite or through a network of groundbased transmitters

Warm Start

The ability of a GPS receiver to begin navigating using almanac information stored in its memory from previous use

Waypoint

A destination. The coordinates of locations along the desired path as measured in geographic coordinates of longitude and latitude

WGS 84

World Geodetic Survey 1984. Geodetic datum for the GPS orbits and consequently positions and baselines computed using them

WGS84

World Geodetic Survey 1984. A common map datum reference

Wide Area DGPS (WADGPS)

Wide Area DGPS. A form of DGPS in which the user's GPS receiver receives corrections determined from a network of reference
stations distributed over a wide geographical area. The corrections are typically supplied in real time by way of a geostationary communications satellite or through a network of groundbased transmitters

Widelane

A linear combination of the L1 and L2 observation (L1 L2) used to partially remove ionospheric errors

WideLane Observable

The GPS observable obtained by differencing the carrierphase observations simultaneously measured, in cycles, on the L1 and L2
frequencies. The effective wavelength is 86.2 centimeters

World Geodetic Survey 1984 (WGS 84)

A common map datum reference. Geodetic datum for the GPS orbits and consequently positions and baselines computed using them

World Radio Conference (WRC)

An international conference where standards and interference issues are discussed

WRC

World Radio Conference, an international conference where standards and interference issues are discussed

X


XTE

Crosstrack Error. The distance you are off a desired course in either direction

Y


YCode

The encrypted Pcode



Z


ZCount

The fundamental GPS time unit. It is a 29bit binary number, of which the 10 most significant bits give the binary representation
of the GPS week number, and the 19 least significant bits give the timeofweek (TOW) count in units of 1.5 seconds



2D Mode

2 Dimensional Mode. A twodimensional GPS position fix that includes only horizontal coordinates, no elevation. It requires a
minimum of three visible satellites

3D Mode

3 Dimensional Mode. A threedimensional GPS position fix that includes horizontal coordinates plus elevation. It requires a
minimum of four visible satellites
