Contours tell you whether the ground is flat, hilly, undulating, or steep. You can tell whether a route will be a gentle stroll or a hard uphill slog, so you can plan your route more easily. Contours are shown on Ordnance Survey maps as thin orange or brown lines with numbers on them that show you the height above sea level of any point on the line. The contour lines join points of equal height together. Contour lines very close together indicate a steep slope and contours further apart show a gentle slope. The vertical interval is the height (elevation) between each contour and they appear 5 or 10 metres apart with thicker lines every 50 metres. The numbers on contour lines are always displayed in ascending height, so if the numbers increase it denotes an uphill slope, and if they decrease it’s a downhill slope. The relationship between higher and lower contours and the distance between them can give you valuable clues about what the real surface of the ground is like: Smaller circles show a summit or basin, but the inside of a contour circle is normally higher ground. Flat areas like river valleys and the sea have very few or no contours. Using contour lines you can calculate the elevation of your route, or height of travel. This is useful because you can add the uphill distance to the length of your route to get a more accurate estimate of the total distance you’ll go. For example, if you measure your route as being 2 km, and the difference between the contours along the way is 500 m, your actual distance is 2.5 km.
Flow maps in cartography are a mix of maps and flow charts, that "show the movement of objects from one location to another, such as the number of people in a migration, the amount of goods being traded, or the number of packets in a network".
*Cartography: Cartographyis the study and practice of making maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively.