Explain how GPS works.

State one data item concerning the arrival of a train that may be provided on the video display.

Outline how sensors can be used in combination with GPS to provide more accurate arrival data.

Outline two pieces of information that the ATrainAway application could provide to the user.

Discuss the advantages and disadvantages of using GPS in transportation systems.

Award [4 max] 
The GPS receiver in a train takes the information from the satellite/ picks up the signals from (at least) 3 satellites;
The signals transmitted are: time of transmission, coordinates of the satellite;
The difference between the (atomic) time of transmission and (atomic) time of receiving the signal is used to calculate the distance;
The method of trilateration is used to determine position from the distance to satellites/ is used to determine the train’s exact position/ is used to calculate position of the train through equation resolution on a sphere;

Award [1 max].
Train number/ route / direction;
Status (on time / delayed / cancelled);
Time train / next train are due;

Award [2 max].
Motion sensors/vibration sensors (can be placed on track rail);
(Accept any sensors which detect trains that pass them!)

(Sensing devices are placed) at a distance from each side of a train station/junction
OR
at some fixed points where obstacles (like tunnels) prevent GPS from working properly;

Data from each sensor can be logged continuously and used in calculations/determinations (of expected arrival times/ delays / rerouting during disruption, etc.);

Award [4 max].
Real-time information (train number/ route / direction and status (on time / delayed / cancelled);
relating to the arrival / departure of a particular train;

The time next train is due (the next 2/3 times a train will arrive at the station);
helps passenger to spend less time waiting on trains;

Should save user's (passenger) most frequented stops and routes;
for quick access to get the next rail trip;

Alerts (set);
to let you know when a train is nearing the station;

Trip planning (conducted);
through Google trip planner within the app;

Information on the nearest station, distance to station/ next train arrival/ next train departure;
to help passenger to spend less time travelling/ save time;

Mark as 2 and 2.

Award [4 max].
Safer transit;
Trains are tracked and in case of emergency the location can be reached at the earliest and emergency services provided;

More favourable view of transit/helps passenger to get punctuality status of the train/;
GPS can provide worldwide three-dimensional positions (24 hours a day) (in any type of weather);

Sometimes it is too difficult to ensure reliable positioning;
Objects, such as buildings, overpasses, and other obstructions (that shield the antenna from a satellite) can potentially weaken a satellite's signal;

Privacy issues;
Knowing the absolute position of anything, anytime, anywhere;

Mark as 2 and 2.

Most candidates knew that a GPS works by communication with satellites. Some candidates failed to achieve full marks as result of incomplete and vague descriptions. A few candidates, for some unknown reasons, wrote that the satellite calculates the train's position. 

Generally, well answered, with many full or near full marks awarded.

Generally, well answered, with many full or near full marks awarded.

This question was well answered with the vast majority of candidates gaining some marks, some of whom achieved full or nearly full marks.

Candidates were usually able to identify the advantages and disadvantages of using GPS in transportation systems. Some marks were lost because of vague discussions.