Set 1 Flashcards
(39 cards)
What is Pseudo Random Noise (PRN) Code?
Pseudo Random Noise (PRN) Code is a complex digital signal that resembles a random sequence of ‘1’ and ‘0’ pulses, allowing receivers to identify which satellite(s) they are receiving.
What are the two Pseudo Random Noise (PRN) Codes transmitted by GPS Satellites?
The two PRN Codes are: 1. C/A (Coarse Acquisition) Code 2. P (Precise) Code
What is the C/A (Coarse Acquisition) Code?
C/A Code is transmitted by every GPS Satellite on L1 Frequency (1575.42 MHz) for civilian GPS Receivers, repeated every millisecond at a bit rate of 1.023 Mbps.
What is the P (Precise) Code?
P Code is transmitted by all GPS Satellites on both L1 and L2 Frequencies, generated at a speed of 10 times faster than C/A Code with a bit rate of 10.23 Mbps, intended for military GPS Receivers.
Why does GPS use two Frequencies?
GPS uses two Frequencies to provide accurate positioning for the US Military, allowing dual frequency receivers to eliminate atmospheric errors.
What are the principles of GLONASS?
GLONASS calculates the distance between a satellite and receiver using the formula: Distance = Travelling Time x Speed, and fixes position using trilateration from at least three satellite ranges.
What is the use of GLONASS?
GLONASS is used for positioning, time adjusting, tracking, and surveillance by both civilian and military sectors.
What is the coverage of GLONASS?
GLONASS has 100% terrestrial coverage and offers better accuracy at higher latitudes compared to GPS.
What are the accuracy standards of GLONASS?
Standard Positioning Service (SPS) accuracy is about 10 meters, while Precise Positioning Service (PPS) accuracy is 1 to 2 inches.
What are the limitations of GLONASS?
Limitations include potential shutdown by the owning country, susceptibility to signal interference, vulnerability to spoofing, and the need for an unobstructed line of sight.
What is Permanent Magnetism?
Permanent Magnetism occurs when iron molecules align with the Earth’s magnetic field during construction, creating a constant magnetic force.
What are the components of Permanent Magnetism?
The components are: 1. F & A (+P, -P) 2. Athwartship (+Q, -Q) 3. Vertical (+R, -R)
What is Induced Magnetism?
Induced Magnetism is temporary magnetism acquired by a ship’s soft iron due to the Earth’s magnetic field.
What are the components of Induced Magnetism?
The components are: 1. Horizontal soft iron, induced by H 2. Vertical soft iron, induced by Z
What is the operating principle of a Transmitting Magnetic Compass (TMC)?
A TMC outputs magnetic compass heading to digital displays using a fluxgate sensor to detect angular deviation of the compass needle.
What is a Free Gyroscope?
A Free Gyroscope is mounted to allow 360° rotation freedom on all axes, including horizontal, vertical, and spin axes.
What is Gyroscopic Inertia?
Gyroscopic Inertia is the property of a spinning rotor to maintain its axis in a particular direction until a force is applied.
What is Gyroscopic Precession?
Gyroscopic Precession is the movement of the spin axis at a right angle to an applied force.
How is a Free Gyroscope made ‘North Seeking’?
Methods include Top Heavy Gravity Control, Bottom Heavy Gravity Control, and Liquid or Mercury Ballistic Control.
What is the Gyro Compass Repeater?
A Gyro Compass Repeater aligns itself to display heading based on signals received from the gyro compass.
How does AIS work?
AIS transmits and receives ship information on VHF Channels using Time Division Multiple Access (TDMA) to share a single frequency.
What frequencies are dedicated for AIS?
87B (161.975 MHz) and VHF Channel 88B (162.025 MHz) are dedicated for AIS.
What access method does AIS use for sharing a single frequency?
AIS uses Time Division Multiple Access (TDMA) for sharing a single frequency.
How is time divided in TDMA for AIS?
In TDMA, every minute is divided into 2250 slots, each 26.6 milliseconds in length.
