Recognising topographic map features
There’s a lot more to topographic maps than first meets the eye. Upon inspection, a user can determine the directions which creeks flow, the depth of a water course, how likely a gully is to contain water, and so on. These can all prove useful for navigating along a track, route finding, figuring out good places to camp, collecting water and so on.
Topographic maps convey natural 3D formations in a 2D format and show how other features match to these formations. Topographic maps depict four main types of features:
- Landforms: hills, valleys, gullies, ridges…
- Water courses: rivers, swamps, coastal…
- Vegetation: national parks, farmland, plantations…
- Manmade: buildings, roads, property boundaries, political boundaries…
Landforms Understanding how landforms are depicted on topographic maps
Landform refers to the shape of the land, and is a function of elevation and relief, that is, the representation, as depicted by the mapmaker, of the shapes of hills, valleys, streams, or terrain features on the earth’s surface. Both elevation and relief allow users to recognise landforms.
Contours and intervals
Contour lines are the most common method of showing relief and elevation on a standard topographic map, and they give a sense of slope. A contour line represents an imaginary line on the ground, above or below sea level. All points on the contour line are at the same elevation. The elevation represented by contour lines is the vertical distance above or below sea level.
The three types of contour lines used on a standard topographic map are index, intermediate, and supplementary.
- Index. Starting at zero elevation or mean sea level, every fifth contour line is a heavier line. These are known as index contour lines. Typically, each index contour line is numbered at some point. This number is the elevation of that line.
- Intermediate. The contour lines falling between the index contour lines are called intermediate contour lines. These lines are finer and do not have their elevations given. There are usually four intermediate contour lines between index contour lines.
- Supplementary. These contour lines resemble dashes. They show changes in elevation of at least one-half the contour interval. Supplementary lines occur where there is very little change in elevation such as on fairly level terrain.
Shading and tinting
Shaded relief can be used to emphasise features. Relief shading indicates changes in shape by a shadow effect achieved by tone and colour that results in the darkening of one side of terrain features such as hills and ridges. The darker the shading, the steeper the slope. Shaded relief is sometimes used in conjunction with contour lines to emphasise these features.
Watercourses Understanding how watercourses are depicted on topographic maps
Shaded blue areas and blue lines identify hydrography or water features. These include lakes, swamps, rivers, and creeks as well as intertidal features and reefs. Maps can also include cultural features such as shipwrecks and patrolled beaches.
Topological maps do not distinguish between saltwater or freshwater systems, although common sense can mostly be used to figure this out: coastal water bodies are likely to salt-water, inland creeks are likely to be freshwater.
Major rivers are indicated as thicker blue lines and often have many smaller side creeks feeding into them. A river that has several smaller creeks feeding into it is more likely to be a permanent source of water than one without.
Perennial versus permanent water sources
Australian water sources depend on local rainfall patterns. Some rivers run all year round, while others only flow after rainfall. A perennial watercourse contains water all year round, and can be thought of as a permanent water source, whereas a non-perennial watercourse intermittently flows depending on local weather and rainfall patterns.
It’s possible to make an educated guess as to whether a watercourse is running based on local rainfall patterns, known water levels and talking to other bushwalkers that have been in that areas recently.
On NSW topographic maps, the weight of a blue line indicates whether it is perennial or not: heavy lines show perennial watercourses, fainter lines show non-perennial.
Vegetation Understanding how different vegetation types are depicted on topographic maps
Shading and symbols show different vegetation types. This topographic map shows a small plantation area on the left between the two images.
Manmade Understanding how manmade features are depicted on topographic maps
Manmade features on a map include physical infrastructure (buildings, roads, fences, tracks) through to human-perceived boundaries (e.g. private properties vs. national parks). Here are some examples below.
Different shapes are used to mark physical features on a map such as roads, pathways, railways lines. Check the map key for more information.
Tracks and trails
Solid orange lines indicate minor unpaved roads, and wide dashes indicate vehicular tracks. These roads are usually two-wheel drivable. Narrow orange dashes are four-wheel drive tracks. Dotted black lines are bushwalking tracks, and can vary from a well-worn concrete track right down to a faint footpad.
Some minor tracks or roads may not be accurately drawn or missing on topographic maps because these tracks overgrown or new roads have been created since the map data was collected. Checking the year of publication of the map can give an indication of how likely the tracks are to be accurate. Tracks and trails sometimes have locked gates: in general, walkers can get across locked gates but cars cannot. The exception is, of course, private property where bushwalkers must get permission to access.
Power transmission lines
Large power lines can be useful landmarks for navigation although minor power lines are likely to have changed since map data publication. Use power transmission lines to determine locations with caution.
In Australia, it is illegal to trespass on private property without permission, regardless of whether a road or walking track runs through the property, or if it is the only access point to a national park.
On NSW topo maps, property boundaries are usually marked in light grey lines and are generally fields shaped into rectangles, rhombus or squares. Sometimes these properties include a number which is the designated title of the private land.
The best course of action is to plan the bushwalking route carefully and check for private property boundaries. If the track passes through a private property then a phone call ahead of time to ask for permission to enter is best. If the owners do not grant permission, do not enter.
Determining where property boundaries lie enables a bushwalker to figure out what is allowed in certain areas. For instance, in NSW dogs are not allowed in national parks, but they are in state forests. Bushwalkers cannot walk on private properties without permission.
Different shades are used to mark regional boundaries (e.g. National Park boundaries, councils, state forests, etc.). Check the key to confirm regional boundaries.
Here there is a National Park boundary for the Nattai National Park, north of the grey boundary line.