A compass is a device that shows the user magnetic north. Contrary to popular belief, it doesn’t instantly tell you where you are! Rather, it’s a tool that bushwalkers use in combination with a map and the landscape to help figure out where they are.
An altimeter is a tool that measures altitude above a reference point. It works by detecting small changes in atmospheric pressure, and bushwalkers can use a hand-held or wrist-mounted device.
Knowing altitude can help to verify the user’s location, particularly on long uphill sections. When used conjunction with a topographic map, a barometric altimeter is often more accurate than a GPS unit, which is susceptible to failure from satellites dropping in an out of availability and being wildly inaccurate when all available satellites are near the horizon.
Since barometric pressure is affected by weather and changes in weather, bushwalkers need to recalibrate the device periodically at a known location (e.g. trail junction, hill).
Compasses have small magnetic needle suspended in fluid that rotates freely around a fixed axle until it settles pointing towards magnetic north.
Bushwalkers can use a compass in two directions: (i) to read a bearing off a map and applying that to real life, or (ii) to read a real life bearing and apply that back to the map. In practical terms, this means that a bushwalker can use a compass to determine the direction from A to B from a map, then follow that bearing in real life. Alternatively, they can take a reading in real life and put it back on the map to help figure out where they are.
A compass enables the user to orientate the map in the direction of sight, helping the user to match map features with the physical surroundings. A compass bearing of a road direction, a creek direction, the orientation of a set of powerlines can also help bushwalkers to determine where the are on the map.
However, compasses do have their flaws. Since they rely on the earth’s magnetic field to align, any strong metal object or magnetic substance nearby can send the needle haywire. For example, metal implants in packs, clothing phones. A common mistake is to set the map up on the bonnet of the car, but the compass will not point north.
In some parts of the world, the ground has high metallic content. Compasses are completely useless in these areas as the compass never points north.
Switching between hemispheres is another common problem with compasses. A northern hemisphere compass doesn’t work in the southern hemisphere and vice versa (unless you have a special compass that can do both).
And once the fluid around the needle gets a bubble in it or leaks, the game is over. The compass is unlikely to be accurate or work ever again. Unfortunately, it’s a common problem when traveling.
Users also have to be aware of magnetic variations and how far off north they are at any given time. The adjustment introduces another degree of human error into the situation.
All that said, people do love compasses. They’re something most people are comfortable with and used to. Just be aware of some of the issues around using them. Don’t forget to fasten your compass securely to your map case or neck so you don’t lose it!
Using a GPS, smartphone or tablet as a navigation tool
A GPS navigation device gives the user their location anywhere on earth. GPS stands for Global Positioning System, a space-based navigation system that uses satellites to identify a location. As long as the device has an unobstructed line of sight to four or more GPS satellites, it’s accuracy is within 20m, more than adequate for all on-track bushwalking needs.
CAUTION: a GPS unit only gives location information. Users must still be able to plan and follow a route, which requires map reading skills.
Knowing location information is useful, but only one component of navigation. It’s no use knowing that your location if you can’t then use that information to get to your destination. Often, going directly from A to B in a straight line is not the best way, or worse, there’s a massive cliff in between. Route planning is about determining the best way to traverse the landscape, and navigation is about executing that plan.
However, just like any tool, GPS technology can fail! For example, the GPS unit might jam up, the batteries could run out, the unit could get dropped, or water gets inside the electronics. On a bigger scale, satellites can drop out or become wildly inaccurate if their position is near the horizon relative to you. A GPS will not work if it doesn’t have an unobstructed line of sight to four or more GPS satellites. For example, at the base of cliffs a GPS will give terrible results, and in dense forest the signal may be faint.
So that’s why it’s a good idea to carry backups. Often, a GPS user will also take a compass as a backup. Likewise, compass users will often bring a GPS unit as their backup.
A map is a diagrammatic representation of an area of land or sea. It shows physical features such as man-made cities or roads, as well as natural landforms like mountains, rivers and cliffs. The purpose of a map is to depict spatial relationships between features. A map can vary from being a highly schematic piece of artwork right through to a meticulously detailed representation of geographic data depending on the purpose of the map.
Understanding maps and their purpose
Cartography is the art of creating maps, and it has evolved over many thousands of years to be as we know it today. Now maps are no longer basic cave drawings but instead produced using computers and other technologies and distributed to the masses.
People create maps for different purposes depending on their audience and what information they need to convey.
Some different map types include:
Physical maps: Depict information on physical features like creeks, mountains and man-made features. Symbols, colours and tinting illustrate variation.
Climate maps: General information about climate and weather in a region (e.g. rain, snow, temperature). Colour depicts variation.
Resource maps: Show different types of natural resources or economic activity in an area. Symbols show activities; colours show differences in land elevation.
Road maps: Show minor and major roads and other human infrastructure e.g. buildings.
Political maps: Show human depicted political boundaries such as private properties, land tenures and National Parks.
Topographic maps: show the shape of the landscape using contour lines. Lines far apart indicate flat ground; lines close together indicate steep ground.
Understanding topographic maps and their purpose
Topographic or ‘topo’ maps are a specific type of map that shows the shape of the land. The map shows 3D landforms on a 2D surface and can be done via colour variation or contour lines that show elevation information too.
Topographic maps are handy tools for planning bushwalking trips and navigating through the bush. Maps enable bushwalkers to plan routes, communicate points of interest and tracks, and keep a track of where they are in relation to resources like water and shelter.
Bushwalkers love topographic maps because they:
Simplify complex patterns.
Facilitate visual connections between landforms.
Enable communication with other walkers, rescue organisations, people at home, etc.
Allow bushwalkers to extract useful info and plan a route to include campsites and water sources, avoid scrubby areas and select good walking ridges.
Provide a universal tool of communication between bushwalks to share trip routes, campsites, water sources, etc. with others.
Datum and Projection
Understanding about datum and projection
All mapmakers have to overcome the fundamental mathematical problem of portraying a spherical object onto a 2D surface. Modern map-makers solve this by taking a ‘datum’, that is, a 3-D representation of the earth, and projecting it onto a 2D plane (i.e. Cartesian x-y coordinates).
This image is the typical one of the Earth centred around Europe. It is produced by converting the curved, spherical lines of longitude and latitude into a flat plane grid of perpendicular lines, but it is severely distorted at the poles.
No model or projection is perfect for every part of the globe, and different countries preference some projections over others to suit their needs.
In Australia, the modern MGA reference system uses the Universal Transverse Mercator projection of the Geocentric Datum of Australia 1994 (GDA94), providing a relatively universal reference system at least for the purpose of recreational bushwalking.
Becoming familiar with the elements of a map makes it easy to switch between different map types and become comfortable with reading and interpreting a large amount of data.
In general, maps contain a grid by which points can be referenced, a scale bar for relating the map to the physical world again, an indication of which direction north is and a key to determine what’s what on the map. It also contains a title and credits to the map maker, projection and geographic data used to create the map. Some maps have locators and insets.
All maps contain a title in a large font that makes the map easy to identify.
In a city, it is quite simple to find a location as the streets are named and the buildings have numbers. The only thing needed is the address. However, locating places in the bush is harder because it’s not a regular daily activity. A uniform referencing system has been developed to help, and now anyone in any location around the world can accurately explain where they are to someone else.
There are the two major coordinate systems that are useful to know for recreational purposes. These are the two main sets of grid lines seen on most topographic maps: (i) the latitude and longitude system and (ii) the Universal Transverse Mercator (UTM) system.
With either system, it’s possible to communicate a location to someone else. For latitude and longitude, the system uses degrees, minutes and seconds. These are the radial positions of lines on a sphere based on a reference point (usually Greenwich, England). For UTM it’s based on a coordinate grid (Eastings and Northings, in metres), although units aren’t included when quoting a grid reference in UTM.
Latitude and longitude lines
Latitude and longitude lines divide the earth into a grid of circular segments: latitude lines are parallel to the equator and run horizontally around the earth. The equator is at zero degrees (0°), and lines run either side from 0° to 90° both north and south. Longitude lines are perpendicular to the latitude lines with 0° running through Greenwich, England. A location is given latitude first, followed by longitude in degrees, minutes and seconds. For instance, Sydney is 33°52.071′ S, 151°12.4392′ E. The S shows that it’s in the southern hemisphere, and E stands for how far East the point is relative to the prime meridian at Greenwich.
The Universal Transverse Mercator (UTM)
The Universal Transverse Mercator (UTM) system divides the earth into a perpendicular set of grid lines measuring surface distances in metres. This system reduces the complexity of transferring a location on a spherical surface to a flat surface (i.e. 2D map).
A UTM position is given by a UTM zone followed by an Easting and Northing. Each UTM zone is 6° wide, and Greenwich England is the reference point. For example, Sydney is in the UTM Zone 56H, and the centre of the city is at UTM Northing 6,252,359.77, and UTM Easting: 334,895.26.
On NSW topographic maps, UTM grid lines are drawn and labelled. Latitude and longitudes are written at the edge of the map area, so it’s possible to locate grid references in terms of degrees, minutes and seconds.
The scale of a map provides a way of comparing what the map represents in terms of the actual distance on the ground.
On NSW topographic maps, the scale of the map is a ratio (e.g. 1:25,000 or 1:100,000), and the scalebar is a ruler divided into kilometres and miles. On a map scaled at 1:25,000, 4 cm on the map equals 1 km on the ground. More literally the ratio says that 1 cm equals 25,000 cm on the ground or 250 m.
For on-track day walks, bushwalkers might be able to get away with a 1:100,000 scale map. But for harder walks and walks off-track, then bushwalkers usually prefer 1:25,000. A 1: 25,000 scale is detailed enough for navigating off-track, and most trips fall over one or two maps.
All maps are orientated to enable the user to related physical on ground features to the map. Most topographic maps used for bushwalking are orientated to true north, which means that the map aligns with the true north/south meridians that connect to the north pole. By contrast, the compass needle points to magnetic north, so when taking bearings on and off the map, the user needs to take the difference between the two norths (magnetic declination) into account.
A map key or legend identifies symbols on the map and indicates what features they represent. It’s usually located in a separate box at one corner of the map and contains colours, symbols, signs or other notation to help the reader interpret the map.
On topographic maps, the key allows users to distinguish between man-made features, natural relief features, vegetation and private vs. public areas.
Map credits inform the reader on the geographical data and projections used to create the map.
Date of map creation
Source and date of geographic data
A locator map connects the area of the map to a bigger or more recognisable (and smaller) scale. For example, Tasmania is often shown in the context of mainland Australia on a locator map. By contrast, insert maps give more detail about a particular area using a larger scale.
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:
Vegetation: national parks, farmland, plantations…
Manmade: buildings, roads, property boundaries, political boundaries…
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.
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.
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.
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.