Tutorial

A-C-D-E-F-G-H-I-L-M-N-P-R-S-T-U-V-W

– A –

almanac Almanacs are approximate orbital parameters for all the SVs. The ten-parameter almanacs describe SV orbits over extended periods of time (valid for months in some cases). The full set of almanacs for all the SVs is sent by each SV over a period of 12.5 minutes (at least). Signal acquisition time on receiver start-up can be significantly aided by the availability of current almanacs. The approximate orbital data is used to preset the receiver with the approximate position and Doppler shift of each SV in the constellation.
A-S Anti-spoofing, under presence of A-S, the P-code is encrypted before emission by the satellites, known as the Y-code.
ASCII The American Standard Code for Information Interchange is a standard seven-bit code. ASCII was established to achieve compatibility between various types of data processing equipment. The standard ASCII character set consists of 128 decimal numbers ranging from 0 . . . 127 assigned to letters, numbers, punctuation marks, and the most common special characters. The Extended ASCII Character Set also consists of another 128 decimal numbers and ranges from 128 . . . 255 representing additional special, mathematical, graphic, and foreign characters.
Azimuth The Azimuth angle of a satellite indicates the direction of the projection of the line-ofsight onto the local horizontal plane measured from the geographic North positive to the East.

– C –

C/A The Coarse/Acquisition code is a pseudo random noise (PRN) binary code consisting of 1,023 elements, or chips, that repeats itself every millisecond. The term pseudo-random indicates that the code is apparently random although it has been generated by means of a known process, hence the repeatability.
channel All the circuitry (software and hardware) needed to receive the signals of one GPS, GLONASS, or SBAS satellite.
chip One bit of a pseudorandom code.
CMR The Compact Measurement Record format contains packet framing and message types for raw L1 and L2 carrier phase and pseudorange data, plus reference station location and description messages.
C/N0 Carrier-to-Noise ratio expressed in [db-Hz].

– D –

DGPS Differential GPS can be used when you have two receivers not too far from each other. The errors due to the satellite clock, the satellite orbit, the ionosphere, the troposphere and SA affect both receivers in the same way and with the same magnitude. If we know the exact location of one receiver, we could use that information to calculate errors in the measurement and then report these errors (or correction values) to the other receiver, so that it can compensate for them.
DNS The Domain Name Server is a distributed Internet directory service. A DNS is used mostly to translate between domain names and IP addresses and to control the Internet e-mail delivery.
DOP The Dilution Of Precision measures the relative degradation of the accuracy of the navigation solution based on the constellation geometry. The reported value can be multiplied by the uncertainty in the range measurements (assumed to be the same for all transmitters) to provide the uncertainty in the navigation solution.
doppler shift This is the change in the frequency of a signal caused by the movement of the transmitter relative to the receiver.

– E –

EGNOS The European Geostationary Navigation Overlay System is the European SBAS system developed by ESA, European Commission and Eurocontrol. Its service zone is the European continental airspace and it is expected to be operational in 2004.
Elevation The Elevation angle of a satellite defines the angle between the local horizontal plane and the direction to the satellite.
ENU The coordinates measured in the topocentric reference with respect to a reference position. The N-axis points to true geographic north, the E-axis is oriented towards the east while the U-axis is along the local normal.

– F –

FTP The File Transfer Protocol is used on the Internet for exchanging files and it is based on the TCP/IP protocol. FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server.

– G –

GNSS The Global Navigation Satellite System is a satellite navigation system which currently includes GPS, its Russian analogue GLONASS and three space-based augmentation systems: EGNOS,WAAS, and MTSAT.
GPS Global Positioning System (also NAVSTAR GPS)is a satellite navigation system owned by the Department of Defence of the United States of America and designed to provide instantaneous position,velocity and time information almost anywhere on the globe at any time, and in any weather. NAVSTAR GPS stands for the NAVigation Satellite Timing And Ranging Global Positioning System.
GUI The Graphical User Interface gives the user a graphical way for controlling and viewing the information of the receiver.

– H –

HAL Horizontal Alert Limit.
HDOP Horizontal Dilution Of Precision is a measure of the uncertainty of the navigation solution in the local horizontal plane.
HMI Hazardously Misleading Information.
HPL Horizontal Protection Level.

– I –

ICAO The International Civil Aviation Organization coordinates standardization, facilitation, regional planning, economics, law and technical cooperation in the field of aviation.
IGS The International GPS Service provides GPS orbits, tracking data, and other high-quality GPS data and data products on line in near real time to meet the objectives of a wide range of scientific and engineering applications and studies.
ILS Instrument Landing System facilities are a highly accurate and dependable means of navigating to the runway. The ILS provides the lateral and vertical guidance necessary to fly a precision approach.
IP The Internet Protocol is responsible for moving packets of data between Internet nodes. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their IP numbers to departments.

– L –

L1 GPS satellites transmit two L-band signals which can be used for positioning purposes. The signals, which are generated from a standard frequency of 10.23 MHz, are L1 at 1575.42 MHz and L2 at 1227.60 MHz and are often called the carriers. The frequencies are generated from the fundamental satellite clock frequency of f0 = 10.23 MHz.
L2 GPS satellites transmit two L-band signals which can be used for positioning purposes. The signals, which are generated from a standard frequency of 10.23 MHz, are L1 at 1575.42 MHz and L2 at 1227.60 MHz and are often called the carriers. The frequencies are generated from the fundamental satellite clock frequency of f0 = 10.23 MHz.
LAN A Local Area Network is a computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines, radio waves, among other ways.
LED Light Emition Diode. Light-emitting diodes are diodes that emit visible light when electricity is applied, similar to a light bulb. RxControl simulates LEDs by animated images.

– M –

MI Misleading Information.
MTSAT Multifunctional Transport Satellite.
MSAS MTSAT Satellite Augmentation System. Space-based augmentation system intended to supply DGPS correction data to improve the accuracy of GPS-based navigation data for Japan’s flight information region. This japanese space-based augmentation system operates according to the same SBAS standards as WAAS and EGNOS.

– N –

NAVSTAR Navigation Satellite Timing And Ranging.
NMEA The National Marine Electronics Association has developed a standard to permit ready and satisfactory data communication between electronic marine instruments, navigation equipment and communications equipment when interconnected via an appropriate interface. The standard implemented by the PolaRx receiver is the NMEA 0183, version 2.30.

– P –

P1 The P(Y) code transmitted on the GPS L1 carrier.
P2 The P(Y) code transmitted on the GPS L2 carrier.
PA A Precision Approach is an approved descent procedure, which uses a navigation facility aligned with a runway where glide slope information is given.
PDA A Personal Digital Assistant is a mobile device which can be used on the field or while being away from a desktop computer. A RxMobile is an application which has been designed for such devices.
PDOP Position Dilution Of Precision is the geometric DOP parameter.
pitch Rotation around the side-to-side axis.
PL SBAS systems generate in real time protection limits for the residual position error in the differential correction to GPS. When the residual error exceeds the protection limit, an alarm is raised notifying the user of a potential dangerous situation.
PRN The Pseudo Random Noise refers to a code that is is apparently random although it has been generated by means of a known process, hence the repeatability of the code indicate by the prefix pseudo random. Each GNSS satellite has its PRN number. pseudo-random code This is a signal with random-noise like properties.
PVT Position, Velocity and Time, meaning that the navigation solution computes the current position, velocity and time clock bias of the receiver. P(Y) The Precise code is a long binary code that would repeat only every 38 weeks. Despite the code being shortened to a one week repeatability, because each satellite transmits a different weekly section of the code, there is still no ambiguity between the satellite and receiver. Under presence of A-S (Anti-Spoofing), the P-code is encrypted with the Y-code.

– R –

RINEX The Receiver INdependent EXchange format is data format independent of receiver type. RINEX can be seen as a standard exchange format for GPS data.
RMS Root Mean Square.
roll Rotation around the front-to-back axis.
RS-232 The RS-232 standard specifies signal voltages, signal timing, signal function, a protocol for information exchange, and mechanical connectors for a serial connection.
RTCM Radio Technical Commission for Maritime Services. The committee NO. 104 of the RTCM recommended a standard for exchange of data for Differential GPS service. The standard addresses both code-based and carrier-phase based positioning. The PolaRx can generate as well as interpret RTCM messages for the purpose of differential positioning. In DGPS applications, the PolaRx can generate and interpret RTCM messages 01, 03 and 16 while for RTK it requires messages 18, 19, 22 and 3. The interpretation of these RTCM messages from publicly available providers is supported if they adhere to the RTCM V2.2 or V2.3.
RTK GPS Real-Time Kinematic is a high-precision surveying method. RTK is based on differential carrier-phase prunning with either float or integer phase ambiguities. RTK requires a real-time data link to transmit correction data from the base station to the rover.

– S –

SBAS A Space-Based Augmentation System is a regional augmentation systems for GPS and/or GLONASS. An SBAS system is based on a networked ground segment and navigation payloads on-board of geostationary satellites whose main purpose is to provide higher position accuracies, better availability and continuity of service and integrity messages to the users of space based navigation systems. Currently existing SBASs are based on DO229 data exchange standard.
SBF The Septentrio Binary Format is a data format used by the Septentrio receivers. It arranges the data in so-called SBF blocks, identified by block IDs. The benefit of SBF is compactness : large quantity of information with a high level of detail can be transmitted over a low-bandwidth serial connection. This format should be your first choice if you wish to receive detailed information from the PolaRx.
sru Files with this extension contain RxControl upgrade info.
suf Files with this extension contain PolaRx upgrade info.
SV Space Vehicle.

– T –

TCP/IP TCP/IP is a communication protocol and is composed of layers: IP : is responsible for moving packets of data between Internet nodes. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their IP numbers to departments. TCP : is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received. Sockets : A name given to the package of subroutines that provide access to TCP/IP on most systems.
TDOP Time Dilution Of Precision is a measure of the uncertainty of the navigation solution in the time determination.
TOW GPS time is transmitted by a combination of the current Week Number and the Time Of Week. The TOW represents the number of seconds into the week ranging from [0 . . . 604800[ seconds and is counted from midnight Saturday/Sunday on the GPS time scale.

– U –

UDRE The User Differential Range Error represents a scale factor with which the 1 differential errors should be multiplied to obtain an estimate of the position accuracy.
UTC Coordinated Universal Time is a time scale that couples Greenwich Mean Time, which is based solely on the Earth’s inconsistent rotation rate, with highly accurate atomic time. When atomic time and Earth time approach a one second difference, a leap second is calculated into UTC. UTC was devised on January 1st, 1972 and is coordinated inParis by the International Bureau of Weights and Measures (BIPM). For most practical purposes associated with the Radio Regulations, UTC is equivalent to mean solar time at the prime meridian (0 longitude), formerly expressed in GreenwichMean Time (GMT). The maintenance by BIPM includes cooperation among various national laboratories around the world. The full definition of UTC is contained in CCIR Recommendation 460-4. The GPS system time is different from the UTC time by a whole number of leap seconds (13 at the time of this writting).

– V –

VAL Vertical Alert Limit.
VDOP Vertical Dilution Of Precision is a measure of the uncertainty of the navigation solution in the vertical direction.
VPL Vertical Protection Level.

–W –

WAAS The Wide Area Augmentation System is the American SBAS system developed by the FAA.WAAS is designed to improve the accuracy and ensure the integrity of information coming from GPS satellites. The FAA is moving directly to a Lateral Navigation/Vertical Navigation (LNAV/VNAV) capability using WAAS with expected capability in 2003.
WGS84 The World Geodetic System 84 is an Earth-fixed global reference frame. It is defined by a set of parameters defining the shape of the earth’s ellipsoid, its angular velocity, the earth mass and a detailed gravity model of the earth. These parameters are needed becauseWGS 84 is used not only for defining coordinates in surveying, but, for example, also for determining the orbits of GPS navigation satellites.
Wn GPS time is transmitted by a combination of the current Week Number and the Time Of Week. The week number represents the number of weeks elapsed since the introduction of the GPS time scale on January, 6th 1980.