GPS Basics
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The Global Positioning System is s a US Government owned network of 24 Satellites around the world.
A GPS Receiver will ask the nearest 5 satellites where it is, & calculates the mean value to locate its position (Latitude & Longitude)..m, as each Satellite already knows where it is
In geometry, you only need 3 satellites to triangulate your position, however 5 can give your position within a few metres of accuracy

Traffic Enforcement Cameras
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In the UK, known as Speed Cameras, These units calculate of a vehicle passes a point, such a s Red Light, or within t points at speed ( aspeedtrap) & photographs the event

Most GPS CAR Receivers include a Trial Software for 6-12 months for the speed traps in the UK , however for these to be updated, a subscription is required. The Locations of these cameras is often updated every 3 months


Maps
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Maps of Great Britain  are  installed on GPS Receivers sold in the UK, with some in higher models including Europe The format of a map & how's its easily understandable is crucial to the success of a GPS product


POI - Points Of Interest or waypoints
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POIs are identifying  markers on a MAP that are usually interesting, such as a public or well known building or feature (e.g. statue). The are exceptionally useful in identifying where you are in a particular place & also helps to orientate you