Outline how a smartphone uses data from GPS satellites to obtain its location.

Rahul has stated the importance of a multi-tier architecture using standard protocols. Explain why this approach is important.

Award [4 max]. 
Award [1] for identifying part of the process that a smartphone uses to obtain its location up to [4 max].

Trilateration;
Uses signal strength and latency based on very accurate atomic clock;
Complex formula taking into consideration the curvature of the earth to arrive at latitude, longitude and altitude;
The smartphone uses the distance between satellites to create overlapping “spheres” that intersect in a circle (which is the phones location);
When fewer satellites are available the accuracy diminishes and may be specified to within a radius only;
Assisted/augmented GPS can help accuracy by adding location information received from or about WIFI networks and the triangulation of cell towers;
The smartphone depends on data received from GPS satellites, but that can be obstructed or distorted by obstruction (e.g. tall buildings), weather or water;

The answer could include the following:

A multi-tier approach for developers provides:
Abstraction of layers;
Less complexity;
Faster development time;
Easier testing;
Work can be divided better amongst teams;
Performance – system can be divided and allocated to many processors/nodes;
Easier addition of clients, databases or logic which does not “break” other layers;

The use of standards and protocols provides:
Future proofing;
Interoperability;
Communication with legacy devices;
Compatibility with best of breed 3rd party products (e.g. firewalls, load balancers, Quality of Service and network monitoring software etc.).
Quick patching of discovered errors, exploits etc.;
Standards and protocols may already be implemented and have available code references or libraries which would reduce development time etc.;
Security updates and upgrades from the community; 

[1–2 marks]
A limited or superficial response that indicates a basic understanding of one or both approaches. Uses little appropriate subject specific terminology.

[3–4 marks]
A competent explanation of the importance of one or both approaches. There is appropriate use of subject specific terminology throughout the response.