NAVSTAR

[′nav‚stär]

(navigation)

A global system of up to 24 navigation satellites developed to provide instantaneous and highly accurate worldwide three-dimensional location by air, sea, and land vehicles equipped with suitable receivers. Derived from navigation system using time and ranging.

GPS

(1) (General Print Server) An IBM mainframe feature that lets TN3270 clients access LPD/LPR printers via the SNA/VTAM network. See TN3270 and VTAM.

(2) (Global Positioning System) A satellite-based radio navigation system run by the U.S. Department of Defense, officially known as NAVSTAR GPS. Other systems worldwide are GLONASS, Galileo, IRNSS and BeiDou). Originally created for the military, today, GPS receivers are built into all smartphones and millions of cars and trucks. See CarPlay and Android Auto.

GPS vs. the Nav
Technically, the GPS is the satellite system, whereas a "navigation system" or "nav" is the receiver that picks up the signals. In practice, people refer to their navs as their GPS. See navigation system, portable GPS and in-dash navigation.

Three or Four Signals Are Required
At least four satellites are on the horizon at all times, which is sufficient to compute the current latitude, longitude and elevation anywhere on earth to within 15 to 70 feet (see latitude). If only three signals are present due to interference, elevation cannot be derived. If fewer than three, the location cannot be computed unless the nav is built into the vehicle and interfaces with the speedometer (see in-dash navigation).

The Satellite System
In six different orbits approximately 12,500 miles above the earth, 24 medium-earth orbit (MEO) satellites circle the earth every 12 hours. They constantly transmit their current time based on atomic clocks and current location on two frequencies in the L-band (L1: 1575.2 MHz; L2: 1227.6 MHz). Most navs pick up L1, while more advanced receivers pick up both for greater accuracy.

The nav calculates the distance to the satellites by comparing the times the transmitted signals were sent with the times received. By knowing the precise locations of the satellites at any given moment, the nav computes the current coordinates using trilateration, a method similar to how ship captains navigated for centuries (see triangulation).

First Launched in 1978
In this decades-old system, satellites are periodically replaced. In addition, worldwide government and commercial monitoring networks use earth stations to improve accuracy; for example, enabling farm equipment to plant ultra-precise rows of crops (see GPS augmentation system). See social navigation, vehicle tracking, reality view, GPS augmentation system, mobile positioning, LORAN, MEO, GNSS, Galileo and geocaching.

An Early Car Nav

In 1996, Sony's NVX-F160 was one of the first vehicle navigation systems, and it was able to find the nearest restaurant and hotel. (Image courtesy of Sony Corporation.)

GPS in the Woods

Portable navigation works everywhere. The flat object pointing up is the antenna. See portable GPS.

Navigation App in a Laptop

The Delorme Street Atlas offers extensive details including satellites in range (#15 just lost signal), elevation (Elv), azimuth (Az) and signal-to-noise ratio (dB). NET means: N=navigation satellite, E=ephemeris data available and T=being tracked (yellow object on dashboard is the GPS antenna).

Navigation App in a Laptop

The Delorme Street Atlas offers extensive details including satellites in range (#15 just lost signal), elevation (Elv), azimuth (Az) and signal-to-noise ratio (dB). NET means: N=navigation satellite, E=ephemeris data available and T=being tracked (yellow object on dashboard is the GPS antenna).

It Doesn't Get Better Than This

Tesla's navigation system is unlike any other. The 17" touchscreen displays more map area than any other nav screen.

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References in periodicals archive

In 1982, the former USSR matched America's NAVSTARs with a new

Proliferation of precision strike: issues for Congress

(1) Deputy Secretary of Defense, memorandum, "NAVSTAR Global Positioning System," December 22, 1973.

The global positioning system: a case study in the challenges of transformation

"If the GPS receiver gives the user a false reading for his location, the target location coordinates based on this false position will also be wrong by the same amount and could result in collateral damage," according to a 2005 video published by the NAVSTAR joint program office.

GPS and Galileo: friendly foes?

The Voice Navigator, NavStar's first commercially available product, is a connected navigation product that interfaces with a wireless phone to create a hands-eyes-free turn-by-turn navigation system through a voice recognition and response system.

NAVSTAR POWERS VOICE NAVIGATOR WITH NAVTEQ U.S. MAP DATA

"A man who identified himself as Mustafa said at least 20 fishing vessels would load the fuel onto the Navstar 1.

Bleeding Iraq dry: lured by immense profits, insurgents, corrupt officials and smugglers are stealing Iraq's oil and driving the country to ruin

It consists of a minimum operational capability of 24 NAVSTAR satellites, in 12-hour orbits, 10,600 miles above the earth.

Chapter 1 Introduction

The 24-channel PSN-2001 receiver can cooperate with Glonass or Navstar satellites and has an automatic switch from one system to another The bomb can be dropped from altitudes between 500 m and 10,000 m at speeds of 550-1,100 kmph.

Shutting the bomb factory: technology so far has proven no match for relatively low-tech bombs in Iraq and Afghanistan

The NAVSTAR satellites of the Global Positioning System can provide your location to an accuracy of 3 meters (10 feet) or better.

Position confusion

This problem does not occur when the NAVSTAR pulse is used to control synchronization and time at which potentials are recorded.

ECDA needs one-pass assessment process

This satellite is the first in a series of eight GPS IIR satellites that Lockheed Martin is modernizing for its customer at the Navstar GPS Joint Program Office, Space and Missile Systems Center, Los Angeles Air Force Base, CA.

Lockheed Martin delivers first modernized GPS satellite

VX-30 was responsible for the release of operational flight programs incorporating and integrating Navstar global positioning system navigation, APG-71 radar high-resolution mapping and the GBU-24 weapons system.

In relentless pursuit of excellence: VX-30 Bloodhounds