GPS & Electronic Navigation Aids Flashcards
What does GPS Stand
Global Positioning System
What does GNSS stand for?
Global Navigation Satellite System
What does AIS stand for?
Automated Identification System
How does AIS work?
A vessel transmits data on itself via VHF and GPS and then this information is displayed on a screen
Name three pieces of information you could find on a vessel on an AIS display?
Name, Callsign, Status, Destination, Type, Speed/Direction, Size, Received
How does Radar work?
Radar sends out a rotating beam of radio frequency waves and captures the echoes back then displays them on a screen
Why is it better to have the aerial mounted as low as possible on the vessel?
The signal strengths are quite week in GPS
True or False?
You should ensure your GPS in on the same datum as your chart
True
What is a waypoint?
Any spot on a chart that you want to use for navigation
What is the symbol for a waypoint?
A square and a cross combined
True or False?
You can string a series of waypoints together to define a route
True
What is the Cross Track Error (XTE)?
It tells us how far off course we are
What are the two ways in which I can use XTE to stay on course?
XTE Alarm
XTE Ladder
When would GPS Web be useful?
High speed navigation
What does GPS stand for
Global Positioning system
what are the 3 elements of a gps system
the satellites transmitting position information, ground stations controlling the satellites, and a personal receiver, which collects and computes the location
how many satellites are required for an accurate fix
4 satilties
how does gps work out location
by taking the time a signal takes to reach your receiver and the speed of light it gives the distance from the satellite. adding 4 more satellites narrows this down to a single location in 3d space
How do gps calculate speed
by comparing two fixes distance, and mesuring the time between fixes
what is the hdcp
horizontal dilution of precision
do you want to have a high or low HDCP to get a good gps fix
a low HDCP
what should you do before using a waypoint from a pilot guide with a GPS
plot the waypoint on a chart to ensure it is what it says it is.
what is the SOG
Speed overground
what is the TTG
time to go, estimated time before arrival at next waypoint
what is the XTE
cross-track error
what is the COG
Course overground
what is the VMG
Velocity Made Good
What is the cross-track error used for
the cross-track error is used for alerting the skipper if the vessel is outside of a certain margin of error from the planned course.
what is the vilocity made good
the speed along the course, taking account for tacking or not going straight towards it
to comply with maritime law, what cant you use a gps for
as a primary means of navigation
