NAVIGATE IN TRACKED OR EASY UNTRACKED AREAS
This unit covers the basic knowledge and skills in off-road navigation in areas where there are tracks or other significant landmarks in situations where extreme environmental conditions are not likely to occur.
On completion of this module, people should be able to:
• select and use a suitable map, understanding possible sources of error and inaccuracies, and map symbols and their use in navigation
• use a compass, with an understanding of its errors
• plan a route, including escape roues, in tracked or easy untracked areas, based on map information, including scale and bearings
• navigate in tracked or easy untracked areas, using map and other aids, estimating distances, bypassing obstacles, identifying features, and plotting an efficient course.
A map is a graphic representation of a particular part of the Earth’s surface drawn to scale from a ‘bird’s eye’ view. There are many types of maps, including topographic, guide books and diagrams, hydrographic, charts and aerial photographs. The amount and type of detail shown on the map will depend on the scale and purpose of the map. For example, a large scale street map that shows footpaths and buildings will be no use for driving long distances along a freeway.
Common features on maps include title, scale, directional reference, legend, border, longitude and latitude, and grid references. Maps can range from the simple to the very complex, but no map can be expected to show every feature of the Earth’s surface. The features shown are usually selected to meet a specific purpose, with colour, symbols and shading used to illustrate how features are arranged and distributed. Suitable maps for paddling are topographic maps, marine charts and guide books.
A topographic map is a detailed large scale map representing features of landform and built environments. It shows relief and slope of the land, vegetation, buildings, watercourses, and so on. Being able to analyse topographic maps is an important skill. It allows us to:
• interpret and describe the surrounding land
• identify relationships between features
• locate particular points, areas and routes
A guide book is a information usually in the form of a route plan written by fellow paddlers. Guide books contain detailed relevant information such as access, difficulty, hazards and obstacles of a a particular area. As the maps may not be detailed, guide books are best used in conjunction with topographic maps or charts.
Charts for marine use have some topographic detail, but concentrate on features at sea level and beneath. They will include tidal information, navigation lights and buoys, and submerged hazards. For marine charts, the legend is a booklet, Chart 5011, Symbols and abbreviations used on Admiralty charts.
There is a growing number of Internet resources with aerial images and maps. Google Earth is perhaps the best known, however most state planning or environment departments and some universities have sites which allow users to view satellite and aerial photos with various versions of maps. These sites are extremely useful for planning and allow detail previously not available to be researched. It is important to check the scale of such images.
LEGENDS AND MAP SYMBOLS
Map symbols are used to show the location of selected features. Many symbols look like the features they represent, and the importance of a feature may be shown by the size of the symbol, the thickness of the line and the colour used. The meaning of each symbol is explained in the map’s legend. which allows us to interpret the features on the map, and provides us with information relating to the scale and contour interval being used. Although many maps use similar symbols it is essential that to check the legend. For example, a blue line may not always indicate a water system.
There is a direct relationship between the size of things on a map and their actual size on the ground. In other words, maps are a scaled down representation of part of the Earth’s surface, and the map’s scale must be shown on it. Scale is the ratio of distances on the map to distances on the ground, and can be expressed in three ways:
1 As a statement, in words: ‘One centimetre represents 100 000 centimetres’ or ‘One centimetre represents one kilometre’
2 As a ratio or representative fraction: 1:100 000 or 1/100 000
3 As a linear scale.
On a marine chart the latitude scale on the east or west edge is the scale of distance: one minute of latitude is one nautical mile (1.852 km). Maps drawn on progressively smaller scales increase the area of the Earth that can be shown, but reduce the amount of detail that can be included. Maps drawn on progressively larger scales decrease the area that can be shown but enable more detail to be shown. This means, for example, that a map drawn to a scale of 1:20 000 covers a smaller area of the Earth’s surface but shows much more detail than a map drawn to a scale of 1:100 000.
Because the scale of a map shows the relationship between distances on the map and distances on the ground it can be used to calculate distances and areas.
USING A MAP
MEASURING DISTANCE ON A MAP
The distance between two points on a map can be found by first measuring the distance shown on the map and then converting it from centimetres to kilometres and/or metres, or on marine charts, nautical miles. The way in which measurement is done may vary. The following method is merely one example:
• To estimate a straight line distance, place the edge of a sheet of paper between the two points and mark on the paper the distance between the points. Place the paper along the map’s linear scale. Read off the distance on the scale.
• To estimate distances along a curved or irregular line, place a sheet of paper on the map and mark off the starting point. Move the paper so that its edge follows the curve, marking each section as you do. Mark the end point and then place your sheet of paper on the linear scale. Read off the distance on the scale.
DIRECTION AND BEARINGS
Direction helps us to determine the relative location of places and may be given as a bearing. Most maps have a directional arrow indicating north, and topographic maps are generally designed so that north is at the top of the map. Just to make sure, check the direction arrow located near the legend. A compass can be used with a map in a number of ways. If we are observing a landscape, for example, we can lay out the map and then turn it around until the
magnetic north arrow on the map is the same as the north shown on the compass. This is called orienting the map. It makes it easy to identify different features, which should be in the same direction as they appear on the map.
The bearing of a feature or place is expressed in terms of degrees from north, measuring the angle from north in a clockwise direction. North is 000°, east is 090°, and so on. (Note that bearings are always three figures to help avoid confusion.) True, magnetic and grid (i.e. map) bearings must be distingushed: 031° T, 038° M and 032° G may be all the same direction.
The location of features on a topographic map can be found by using grid and area references. Grid lines are a series of numbered vertical and horizontal lines drawn on a map. The horizontal lines are called northings and the vertical lines are called eastings. Northings are numbered from the south to the north (bottom to top), and eastings are numbered from west to east (left to right). To locate relatively small features on a topographic map a six figure grid reference is normally used. The first three digits refer to the eastings and the last three digits refer to the northings.
Each set of three figures is referred to as a co-ordinate. The first two digits of each co-ordinate refer to the eastings and northings that surround the map.
The third digit is obtained by dividing each easting and northing into tenths. Example 1: Grid reference of point A Point A is located exactly on the intersection of easting 24 and northing 39.
The easting is therefore 240 (24 and zero tenths towards 25). The northing is 390 (39 and zero tenths towards 40). The grid reference of point A is 240 390. Example 2: Grid reference of point B
Point B is located four tenths of the way between easting 23 and 24. The easting is therefore 234 (23 and four tenths towards 24). The northing is approximately eight tenths of the way between northings 37 and 38 so therefore it is 378. The grid reference of point B is 234 378.
Some map features (for example a lake or forest) can cover a relatively large area within a grid square. These features are usually located by means of a area reference. An area reference has only four digits. To find the area reference of a feature we first identify the easting line immediately before it and then the northing below it. This means that we refer to the eastings and northings of the lower left-hand corner of the grid square.
Where a feature extends beyond the one grid squares, the area should be based on the lower left-hand corner of the square that contains the main part of the feature.
Example: The area reference of the lake is 2139.
LATITUDE AND LONGITUDE
On a marine chart latitude and longitude are used, not an arbitrary grid. Latitude is the angular distance north or south of the equator, measured in degrees, minutes and seconds: Adelaide is 34° 55' 42" S Longitude is the angular distance east or west of the Greenwich meridian, also measured in degrees, minutes and seconds: Adelaide is 138° 35' 12" E Minutes are often given in tenths rather than seconds (sixtieths).
Contour lines join places of equal height above sea level. Being able to interpret contour lines provides information about:
• the shape of the land
• the slope of the land
• the height of features above sea level.
Each contour line represents a particular height above sea level. The spacing of the contours on a map indicates the steepness of slopes. Areas where contour lines are close together have steep slopes, and areas where there are few contour lines widely spaced are very flat; where they are close the gradient is steep. The contour interval is the difference in height between two adjacent contour lines.
ON THE GROUND
ESTIMATING DISTANCES AND TIME
An important part of trip planning to consider the distance ahead and the time needed to cover it. There are many different factors that will affect the speed of a group, including type of travel, load, weather conditions, terrain, and the ability and size of the group itself. Taking these variables into account, there are a few methods of judging distance travelled and the time still required to travel. For example, an experienced trekker who knows their paces over 100 meters can count their steps, establish the gradient of the route and thus estimate the distance travelled in a particular time frame. Alternatively they can measure the distance between two features on a map, and time their journey between these features to estimate their speed. As a paddler, similar techniques may be adopted with counting strokes and measuring time taken to travel between prominent features. Note that only practice and experience will enable accurate distance and time estimates. For sea kayakers, a speed of 3 kn (3 nautical miles per hour) can be used in planning.
A compass is a navigational instrument consisting essentially of a freely moving magnetised needle aligning itself with the Earth’s magnetic field, indicating north and south. A compass is an essential item when navigating in difficult or trackless areas, and has these main features:
The magnetic compass is subject to two errors: variation and deviation. Variation comes about because the Earth’s magnetic field is not aligned with the geographic poles: compasses point to magnetic poles, not the true poles. Variation varies across the Eath’s surface, and through time. Maps and charts will indicate the amount of variation, whether it is east or west, the year it was measured, and the rate of change.
Deviation is caused by magnetic objects near the compass. Make sure you are not near iron, steel or electronic objects when you use the compass. In canoes and kayaks, stow the cans and radios away from the compass. When you are navigating you will need to convert between Magnetic and True bearings.
The rhyme ‘Variation east, magnetic least; variation west, magnetic best’ may help to remember whether to add or subtract.
FINDING THE DIRECTION TO TRAVEL
A compass is primarily used as an aid to get from one location to another. It provides a direction in which to travel. To take a compass bearing:
1 draw the desired route on the map
2 orient the map to north using the magnetic arrow on the compass
3 line up the ‘Direction of travel arrow’ on the compass to the line on the map
4 rotate the compass housing so that the orientation marks sit over the magnetic north arrow
5 read off the compass bearing
6 add or subtract the magnetic variation as required
7 travel on this set bearing.
A kayak, especially a sea kayak, may have a fixed compass, mounted well forward on deck rather than a hand compass. The paddler will then use it to steer a course. The intended track will be drawn on the chart from departure point to destination and the bearing measured. On a marine chart it is customary to read the bearing from the nearest compass rose on the chart with parallel rules, but protractors can also be used.
An important part of planning a trip is choosing the route to be taken. Choosing a route in tracked areas is simple, as most of the trip will involve following a path or water course. In untracked areas, or areas where you will be relying on a compass bearing, careful route choice becomes essential. A number of factors will affect the final route selection. Some of these are:
• objectives of the session
• time available
• nature of terrain
• weather conditions
• type/amount of equipment
• ability of group
• specific logistical considerations of the trip (i.e. accessibility, communications, emergency escape routes, etc.)
In untracked areas a thorough understanding of the area is vital, through diligent study of the map and, if permitting, a visual inspection of the route itself
Some general principles can be applied to aid in route selection. A hiker, for example, might chose to follow a ridge-line where vegetation is sparse, rather than a creek-line where vegetation is thicker. Likewise, a paddler would find a journey easier following the tide or flow of a river, rather than moving against it. A group on an extended expedition might also need to remain near a water supply
All these factors are interlinked, and most depend on the specifics of the trip itself.
Remember that sound route choice can only be made through thorough understanding of the area of operation.
In untracked areas expect to come across an obstacle of some type, which could be anything from a cliff edge or waterfall, to a locked gate or sandbank. Likewise, obstacle negotiation could range from the simple act of walking or paddling around the obstruction, to changing the whole direction of the trip. Its size and effect on the trip will depend on the leader’s evaluation of the circumstances (group’s ability, risks involved, etc). The method used to bypass an obstacle will largely depend upon the nature of the obstacle. In untracked areas and navigating on compass bearings it is critical that the obstacle can be bypassed without losing either the route or the set bearing.
An example: while hiking in an untracked area (on a bearing of 360°) you have encountered a body of water (Diagram next page):
1 judge the size of the obstacle
2 set a bearing 90° off from original (360–90 = 270°)
3 walk on that bearing (270°) until clear of obstacle face
4 revert bearing to original (360°)
5 walk on original bearing(360°) until clear of obstacle width
6 reverse bearing 90° (360 + 90 = 090°)
7 walk on new bearing (090°) same distance as in step 3 8 Reset original bearing (360°) and continue.
PLOTTING A COURSE
Unlike bushwalkers who can stop and spread out their maps paddlers have limited deck space and never really stop, even when they are not paddling. Everything needs to be prepared and plotted in advance: route, alternates, distances, estimated times...
The prepared map or chart should contain at least:
• the course(s) with bearings marked
• distance marked along the course
• expected times along the course
• any transits (lining up of features) should also be marked for easy reference
• any notes on hazards, etc. should also be noted
It then needs to waterproofed, either by lamination or enclosed in a waterproof case, and then fixed on deck, readily visible, but secured so that it is not washed off
NAVIGATION DATA SHEET OR FLOAT PLAN
As part of your planning you should complete a navigation data sheet (or float plan). It will not only help in the route choice, but will indicate specific information regarding the group’s itinerary, estimated times, locations and trip specific considerations. Once completed, a navigation data sheet should be copied and distributed to the leader or guide, the assistant leader or guide, and the organisation’s office.
This will ensure that if any problems occur that enough people know of the group’s whereabouts at specific times, so an effective response can be organised. National Parks and Wildlife in most States require that commercial or educational groups submit their plan to them. Often the requirement includes submitting the plan to the local police or rescue services as well. You need to check on the local requirements before embarking on any trip. Even on longer personal trips it is beneficial to submit your plans: it allows National Parks to inform you if back burning or other control processes are occurring in your area. It also gives them knowledge of your position in the event of bush fires or other environmental hazards. A minimalist format is shown on the next page, and a more comprehensive form is elsewhere in the resources.
MAP TO GROUND RECOGNITION
In difficult or trackless areas, it is quite easy to either lose the path (if there is one to follow), or lose your sense of direction. In these circumstances a compass is invaluable, but there will be an occasion where either the bearing is misread or misjudged, or the map is inaccurate. The most important skill in navigating is the ability to visualise the map’s description of the land and apply it to what you can see (and should see) around you. In simple terms, to visualise the map three dimensionally. In this way an experienced navigator needs only a map to travel in even the most difficult trackless terrain. In thick vegetation it can be difficult to locate large features shown on the map, but the lie of the land can give you a clue as to your surroundings.
Let’s say you are trying to find a creekline, for example. The contour lines on the map can be translated to a gradient on the ground, and this can you give a direction to follow. Similarly, translating the ridgelines and spurs on the map and applying them to the ground around you can be all you need to relocate your position.
By doing this it is possible to navigate by the use of features, no matter how subtle, as well as (or even without) your compass. Interpreting what a map says and applying it to the ground around you, map to ground recognition, is a skill that increases with experience and is fundamental to navigation in difficult, trackless areas.
It may be necessary to conduct a search of an area, perhaps for a particular reference point or object. A common system of search is the spiral method. Simply start at a single point and move in a circular fashion outwards. As you move increase the diameter of the circle to form a spiral. This method is most useful for locating small point objects (e.g. a trig point). Another method of search for smaller points (e.g. lost objects) is the sweep method. Identify an area appropriate to the size of your group, form an extended line and sweep through the area, making sure that each member keeps equal spacing and holds the line.
More appropriate in locating larger points, features or areas (e.g. campsite or water course) is the area box method. To carry out a box search, walk out from your start point as far as you can without losing visual contact with it (this is called one visual distance). Search around in a perimeter fashion from your central start point. If needed, walk out a second visual distance and again sweep the perimeter. With this box method, it is easy to search a large area in a fairly short time frame but it is not as thorough as the previous two search patterns.
When heading towards a particular point on a linear feature it is sometimes more prudent to aim off. In the diagram a group is travelling through an untracked area towards a bridge over a river. If the group aims directly for the bridge (unbroken line) and fails to find it when they reach the water they would be unsure of which direction the bridge lies. They would then have to conduct a search both ways along the river. If however, the group decides to travel slightly off their compass bearing (path A or B), they will end up definitely on one particular side of the bridge, so would be sure of which direction to find it.
BACKBEARINGS AND RESECTIONS
A backbearing is the 180° opposite bearing on which you are travelling. To work out a backbearing, simply add or subtract 180° from the original bearing. For example, if you are travelling on a bearing of 120°, the backbearing would be 300°, the exact opposite direction (i.e. the direction back down your trail).
Backbearings are useful in retracing your steps, guiding people into your location, and locating your position in reference to someone or something (i.e. a feature).
A resection is a technique used to locate your position on a map. It can be used if you know you are somewhere on the map, but unsure of the exact location. As with all of the skills of navigation, although fairly simple in theory, resections require practice for accuracy. The steps:
1 identify three prominent features on the ground and on the map (the more distinct, the better)
2 take compass bearings to them
3 convert to grid bearings (add or subtract variation as required)
4 convert them to backbearings (+/- 180°) or simply use the compass backwards
5 draw in bearings on map to form a triangle of error (where the lines intersect)
6 locate your position inside the triangle using map to ground recognition. A resection is a valuable technique in locating your position when you think you are lost
ADDITIONAL NAVIGATIONAL AIDS
There are many more aids besides a map and compass available to the navigator. Mariners for hundreds of years have relied upon the use of the sun and the stars for precise position fixes. The Southern Cross constellation at night and the Sun during the day can be used to estimate direction.
To estimate true north during the day, for example, orient your analog watch — set to standard, not daylight saving, time — so that 12 o’clock faces the Sun (i.e. face your watch the opposite way shadows are falling). Identify the angle created by 12 o’clock and the hour hand. Bisect this angle to locate true north. Because of changes in day length between summer and winter, this method can be in error by as much as 30°.
The Global Positioning System (GPS) can locate your position by the use of satellites to better than 25 m accuracy. Although very user-friendly, GPS receivers are affected by tree cover, weather conditions and battery power. They are an excellent aid, but like all aids, should never be used without the backup of a map, compass, and — most importantly — knowledge of the location.
In 2000 Australia changed to a new geodesic datum, GDA94, equivalent to the WGS84 datum used by GPS. Maps based on GDA94 will bear the GDA logo and a table for converting latitude and longitude and the Australian Map Grid between old and
new data. Charts will have notes referring to WGS84 and satellite derived positions. Be aware of the need to convert if you are using a mix of old and new maps or charts, or are using GPS with old maps.
This module was written and illustrated by Peter Carter, based on earlier material.