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DGPS
Differential Global Positioning Systems (DGPSs) supplement and enhance the positional data available from global navigation satellite systems (GNSSs). A DGPS for GPS can increase accuracy by about a thousandfold, from approximately to . DGPSs consist of networks of fixed position, ground-based reference stations. Each reference station calculates the difference between its highly accurate known position and its less accurate satellite-derived position. The stations broadcast this data locally—typically using ground-based transmitters of shorter range. Non-fixed (mobile) receivers use it to correct their position by the same amount, thereby improving their accuracy. The United States Coast Guard (USCG) and the Canadian Coast Guard (CCG) each run DGPSs in the United States and Canada on longwave radio frequencies between and near major waterways and harbors. The USCG's DGPS was named NDGPS (Nationwide DGPS) and was jointly administered by the Coast Guard and the U.S. Departmen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DGPS Reference Station
Differential Global Positioning Systems (DGPSs) supplement and enhance the positional data available from global navigation satellite systems (GNSSs). A DGPS for GPS can increase accuracy by about a thousandfold, from approximately to . DGPSs consist of networks of fixed position, ground-based reference stations. Each reference station calculates the difference between its highly accurate known position and its less accurate satellite-derived position. The stations broadcast this data locally—typically using ground-based transmitters of shorter range. Non-fixed (mobile) receivers use it to correct their position by the same amount, thereby improving their accuracy. The United States Coast Guard (USCG) and the Canadian Coast Guard (CCG) each run DGPSs in the United States and Canada on longwave radio frequencies between and near major waterways and harbors. The USCG's DGPS was named NDGPS (Nationwide DGPS) and was jointly administered by the Coast Guard and the U.S. Departme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Based Augmentation System
Augmentation of a global navigation satellite system (GNSS) is a method of improving the navigation system's attributes, such as precision, reliability, and availability, through the integration of external information into the calculation process. There are many such systems in place, and they are generally named or described based on how the GNSS sensor receives the external information. Some systems transmit additional information about sources of error (such as clock drift, ephemeris, or ionospheric delay), others provide direct measurements of how much the signal was off in the past, while a third group provides additional vehicle information to be integrated in the calculation process. Satellite-based augmentation system Satellite-based augmentation systems (SBAS) support wide-area or regional augmentation through the use of additional satellite-broadcast messages. Using measurements from the ground stations, correction messages are created and sent to one or more satel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selective Availability
The error analysis for the Global Positioning System is important for understanding how GPS works, and for knowing what magnitude of error should be expected. The GPS makes corrections for receiver clock errors and other effects but there are still residual errors which are not corrected. GPS receiver position is computed based on data received from the satellites. Errors depend on geometric dilution of precision and the sources listed in the table below. Overview User equivalent range errors (UERE) are shown in the table. There is also a numerical error with an estimated value, \ \sigma_ , of about . The standard deviations, \ \sigma_R, for the coarse/acquisition (C/A) and precise codes are also shown in the table. These standard deviations are computed by taking the square root of the sum of the squares of the individual components (i.e., RSS for root sum squares). To get the standard deviation of receiver position estimate, these range errors must be multiplied by the a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wide Area Augmentation System
The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area.Federal Aviation Administration (FAAFAQ for WAAS/ref> It may be further enhanced with the Local Area Augmentation System (LAAS) also known by the preferred ICAO term Ground-Based Augmentation System (GBAS) in critical areas. WAAS uses a network of ground-based reference stations, in North America and Hawaii, to measure small variations in the GPS satellites' signals in the western hemisphere. Measurements from the reference stations are routed to master stations, which queue the received Deviation Correction (DC) and send the correction messages to geostationary WAAS satellites in a ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Navigation Satellite System
A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high precision (within a few centimetres to metres) using time signals transmitted along a line of sight by radio from satellites. The system can be used for providing position, navigation or for tracking the position of something fitted with a receiver (satellite tracking). The signals also allow the electronic receiver to calculate the current local time to a high precision, which allows time synchronisation. These uses are collectively known as Positioning, Navigation and Timing (PNT). One set of critical vulnerabilities in satellite communications are the signals that govern positioning, navigation and timing (PNT). Failure to properly secure these transmissions could not only disrupt satellite networks but wreak havoc on a host of dependent s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-directional Beacon
A non-directional beacon (NDB) or non-directional radio beacon is a radio beacon which does not include directional information. Radio beacons are radio transmitters at a known location, used as an aviation or marine navigational aid. NDB are in contrast to directional radio beacons and other navigational aids, such as low-frequency radio range, VHF omnidirectional range (VOR) and tactical air navigation system (TACAN). NDB signals follow the curvature of the Earth, so they can be received at much greater distances at lower altitudes, a major advantage over VOR. However, NDB signals are also affected more by atmospheric conditions, mountainous terrain, coastal refraction and electrical storms, particularly at long range. The system, developed by United States Air Force (USAF) Captain Albert Francis Hegenberger, was used to fly the world's first instrument approach on May 9, 1932. Types of NDBs NDBs used for aviation are standardised by International Civil Aviation Orga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Positioning System
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver. The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canadian Coast Guard
The Canadian Coast Guard (CCG; french: links=no, Garde côtière canadienne, GCC) is the coast guard of Canada. Formed in 1962, the coast guard is tasked with marine search and rescue (SAR), communication, navigation, and transportation issues in Canadian waters, such as navigation aids and icebreaking, marine pollution response, and support for other Canadian government initiatives. The coast guard operates 119 vessels of varying sizes and 23 helicopters, along with a variety of smaller craft. The CCG is headquartered in Ottawa, Ontario, and is a special operating agency within Fisheries and Oceans Canada (Department of Fisheries and Oceans). Role and responsibility Unlike armed coast guards of some other nations, the CCG is a government marine organization without naval or law enforcement responsibilities. Naval operations in Canada's maritime environment are exclusively the responsibility of the Royal Canadian Navy. Enforcement of Canada's maritime-related federal statutes m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Navigation
Radio navigation or radionavigation is the application of radio frequencies to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiodetermination. The basic principles are measurements from/to electric beacons, especially * Angular directions, e.g. by bearing, radio phases or interferometry, * Distances, e.g. ranging by measurement of time of flight between one transmitter and multiple receivers or vice versa, * Distance ''differences'' by measurement of times of arrival of signals from one transmitter to multiple receivers or vice versa * Partly also velocity, e.g. by means of radio Doppler shift. Combinations of these measurement principles also are important—e.g., many radars measure range and azimuth of a target. Bearing-measurement systems These systems used some form of directional radio antenna to determine the location of a broadcast station on the ground. Conventional navigation techni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Executive Order (United States)
In the United States, an executive order is a directive by the president of the United States that manages operations of the federal government. The legal or constitutional basis for executive orders has multiple sources. Article Two of the United States Constitution gives presidents broad executive and enforcement authority to use their discretion to determine how to enforce the law or to otherwise manage the resources and staff of the executive branch. The ability to make such orders is also based on expressed or implied Acts of Congress that delegate to the president some degree of discretionary power ( delegated legislation).John Contrubis, '' Executive Orders and Proclamations'', CRS Report for Congress #95-722A, March 9, 1999, Pp. 1-2 The vast majority of executive orders are proposed by federal agencies before being issued by the president. Like both legislative statutes and the regulations promulgated by government agencies, executive orders are subject to judicial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
President Of The United States
The president of the United States (POTUS) is the head of state and head of government of the United States of America. The president directs the Federal government of the United States#Executive branch, executive branch of the Federal government of the United States, federal government and is the Powers of the president of the United States#Commander-in-chief, commander-in-chief of the United States Armed Forces. The power of the presidency has grown substantially since the first president, George Washington, took office in 1789. While presidential power has ebbed and flowed over time, the presidency has played an increasingly strong role in American political life since the beginning of the 20th century, with a notable expansion during the presidency of Franklin D. Roosevelt. In contemporary times, the president is also looked upon as one of the world's most powerful political figures as the leader of the only remaining global superpower. As the leader of the nation with t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bill Clinton
William Jefferson Clinton (Birth name, né Blythe III; born August 19, 1946) is an American politician who served as the 42nd president of the United States from 1993 to 2001. He previously served as governor of Arkansas from 1979 to 1981 and again from 1983 to 1992, and as attorney general of Arkansas from 1977 to 1979. A member of the Democratic Party (United States), Democratic Party, Clinton became known as a New Democrat, as many of his policies reflected a centrist "Third Way" political philosophy. He is the husband of Hillary Clinton, who was a United States senator, senator from New York (state), New York from 2001 to 2009, United States Secretary of State, secretary of state from 2009 to 2013 and the Democratic nominee for president in the 2016 United States presidential election, 2016 presidential election. Clinton was born and raised in Arkansas and attended Georgetown University. He received a Rhodes Scholarship to study at University College, Oxford and later ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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