18.10.4 Describe and apply the following position reference methods:
(a) place/ bearing/distance;
(b) latitude and longitude;
(c) earth based navigation aids.

Ground Speed is the speed of an aircraft with reference to the ground.

The aircraft’s airspeed is affected by the wind, and the result is the Ground Speed.  

Flying along at 100kts airspeed, with a 20kt headwind (blowing us backwards) our ground speed will be 80kts. 

18.6.4 Measure distances up to 1000nm ( 1%) on an appropriate chart.

To measure distance on a chart, first you must use an appropriate ruler with the appropriate scale. 

Then accurately measure (1% error margin) from the starting point of the route to the finishing point, reading off the length of the track or route against the scale on the ruler. 

b

A small circle is any circle drawn onto the surface of the earth that does not cut through the center. All lines of latitude are small circles except for the equator that is also a great circle

All circles drawn onto a globe that do not pass through the center are considered small circles

You have used 23 litres of fuel in 7.5minutes.
What was your Fuel Flow

18.58.2 Define and calculate:
(a) time and distance to the point of no return (PNR);
(b) time and distance to a departure/destination equi-time point (ETP).

point of no return (PNR)

departure/destination equi-time point (ETP)

Equi-time Point is important to know when you have a problem you need to know quickly  what to do, are you go return to your departure point or carry on to your destination.

Notes:

Given that you need to workout a general half way point with these calculations, however ground speed out and back could be different thus move the actual position you are looking for.

So that we need here is to set up a ratio using the Ground Speeds.
( frac{1}{1+1} )  or ( frac{1}{2} ) Which Halfway or .5 
( frac{GS Home}{GS out +GS Home} )  GS Out and GS Home are the same the then equal to Halfway or .5 

Working with a Head Wind our ground home is more than our ground speed out

( frac{GS Home=2}{GS out=1+GS Home=2} ) = ( frac{2}{1 +2} ) = ( frac{2}{3} ) now our ETP is passed Halfway or .66

Working with a Tail Wind our ground home is less than our ground speed out

( frac{GS Home=1}{GS out=2+GS Home=1} ) = ( frac{1}{2 +1} ) = ( frac{1}{3} ) now our ETP is before Halfway or .33

18.70.2 Explain the limitations of using GPS/GNSS to supplement normal visual navigation.
Sub Topic Syllabus Item

18.50.2 Describe the techniques, requirements, and procedures for:
(a) re-establishing position if lost or unsure of position;
(b) diverting from the pre-planned route;
(c) navigating at low level when forced to do so by bad weather;
(d) amending SARTIMES.

.

18.48.2 Describe the techniques and procedures for:
(a) setting heading;
(b) cruise routine/activity cycle;
(c) maintaining a flight log;
(d) turning points;
(e) approaching/rejoining at a destination aerodrome.