How each extract is made
The land is a random relief model with 20 m contour lines, a river cut into its own valley, roads that follow the gentlest route, a small town, cultivated lands and a plantation. The extract sits at a made-up spot inside South Africa, so its sheet number is a real South African 1:50 000 sheet. The frame shows latitude and longitude with a tick every minute and half minute, and the lettered blocks name places in the questions. Places used for coordinates sit at least 8 seconds from a minute line, so the answer is never on a boundary.
A worked declination
Map SAMAP2 says: mean magnetic declination 26°57' west of true north (2017), mean annual change 3' westwards. For 2026 the difference is 9 years, so the total change is 9 × 3' = 27'. The change is westwards, so add it: 26°57' + 27' = 26°84', and 60 minutes carry into a degree: 27°24' west of true north. A true bearing of 078° then gives a magnetic bearing of 105°24'. Open map SAMAP2
Questions
How do you calculate magnetic declination for the current year?
Find the difference in years between now and the year on the map. Multiply it by the mean annual change to get the total change. If the change is westwards, add it to the declination on the map; if eastwards, subtract it. Carry every 60 minutes into a degree, and say west of true north.
How do you calculate magnetic bearing?
Measure the true bearing clockwise from true north, then add the magnetic declination for the current year: magnetic bearing = true bearing + magnetic declination. In South Africa the declination is west of true north, so you always add it.
How do you calculate average gradient?
Gradient = vertical interval ÷ horizontal equivalent. The vertical interval is the difference in height in metres. The horizontal equivalent is the distance on the map in cm × 500 on a 1:50 000 map. Divide both by the vertical interval and write the answer as a ratio, such as 1 : 40, with no units.
How do you calculate vertical exaggeration?
Vertical exaggeration = vertical scale ÷ horizontal scale. A vertical scale of 1 cm represents 20 m is 1 : 2 000, and the horizontal scale is 1 : 50 000, so the exaggeration is 50 000 ÷ 2 000 = 25 times.
How do you give latitude and longitude from a topographical map?
Latitude first, then longitude, in degrees, minutes and seconds. Find the minute lines on either side of the place, measure how far past the first line it is, divide by the length of one minute and multiply by 60 for the seconds. Always write S and E: without them the answer gets no marks.
How do you calculate area on a 1:50 000 map?
Measure the length and breadth of the rectangle in centimetres and multiply each by 0,5 to get kilometres. Then area = length × breadth in km². A block 3,4 cm by 2,2 cm is 1,7 km × 1,1 km = 1,87 km².
Is this a real NGI topographical map?
No. Every extract here is invented: the land, the farm names and the symbols are our own drawings, at made-up coordinates. It is not affiliated with the Department of Basic Education or National Geo-spatial Information. Practise on past papers as well.
Sources, checked 25 October 2026: DBE, Self-Study Geography Mapwork Grades 10 to 12 (PDF, 2010): scale, magnetic bearing, coordinates, gradient, vertical exaggeration and the sheet numbering; DBE, NSC Geography Paper 2 marking guidelines, May and June 2024: vertical exaggeration and area; NSC Geography Paper 2 marking guidelines of November 2023 (declination with a westwards change, distance range) and November 2024 (bearing range of 1°, gradient 1 : 39,96).