Nuclear reactions can be used in the following except

Map scale shows relationship between map distance and actual ground distance. Scale 1:50,000 means 1cm on map = 50,000cm (500m) on ground. Larger scale = more detail, smaller area.

Contour lines connect points of equal elevation. Close contours = steep slope, widely spaced = gentle slope. Contour interval is the height difference between adjacent lines.

Conventional symbols represent features: blue for water, green for vegetation, black for roads and buildings. North arrow shows orientation. Grid references locate specific points using coordinates.