Johnny Boy's Walkabout Blog

Measure

Metal objects can affect the magnetised needle in a compass, so move away from such objects. Always hold the compass level.

To determine a magnetic bearing from where you are to a visible feature, hold your compass level and:

• point the Direction of Travel Arrow at the feature
• turn the Graduated Dial so that the red N lines up with the red end of the compass Needle
• read the Magnetic bearing at the Index Line.

To measure a grid bearing on a map:

• align a side edge of the baseplate of your compass against the two points between which the grid bearing is to be determined. It might be your current location and your desired destination
• make sure the Direction of Travel Arrow points to the destination or you will get a bearing 180° out
• turn the Graduated Dial so that the Orienting Lines and Arrow align with the Eastings on the map
• read the Grid Bearing at the Index Line.

To convert a Magnetic bearing to a Grid bearing (in all but the SW of WA in Australia), Add the grid-magnetic angle.

Use a memory association to quickly recall MGA. I remember an old MG (Morris Garages) model A sports car. But you can always go back to first principles and draw/imagine the bearing line on the North Point diagram.

MGA

Obviously, the angle from MN to the red bearing line is smaller than the angle from GN to the red bearing line, So MGA.

To convert a Grid bearing to a Magnetic bearing (in all but the SW of WA in Australia), Subtract the grid-magnetic angle.

Use a memory association to quickly recall GMS. I learned mine in the Army Reserve many years ago and it’s not worth repeating. Perhaps you could remember Get More Sausages. But you can always go back to first principles and draw/imagine the bearing line on the North Point diagram.

GMS

Obviously, the angle from GN to the red bearing line is greater than the angle from MN to the red bearing line, So GMS.

Turn the map so that features on the map line up with the same features you see on the ground.

What happens when you can’t see nearby features on the ground (eg. you’re deep in a gully, in a whiteout)?

Align GN with MN, then correct for Grid-Magnetic angle.

Method 1

• Align the Orienting Lines with an Easting on the map grid
• Rotate the map until the north (red) end of the magnetic needle aligns with the Orienting Arrow
• Adjust for the grid-magnetic angle.

Method 2

• Place the compass on the map, with an edge of the baseplate parallel with an Easting and the Direction of Travel arrow pointing to Grid North
• Rotate the map until the red end of the compass needle aligns with the Index Line
• Adjust for the grid-magnetic angle.

• take the compass bearing – hold the compass level; point the direction of travel arrow at the feature; turn the compass housing until the N (red) end of the needle aligns with the orienting arrow; read the magnetic bearing at the index line
• convert the bearing from Magnetic to Grid – MGA
• turn the compass housing so that the grid bearing lines up with the index line
• place corner of baseplate at current location. Rotate the whole compass until the orienting lines are parallel with the Eastings. Ensure the orienting arrow is pointing North
• the feature will be along the line of the side of the baseplate.

• measure the grid bearing – align a side of the baseplate between your known location and the desired feature, with the direction of travel arrow pointing to the desired feature; rotate the compass housing until the orienting lines are parallel with the Eastings; read the grid bearing at the index line
• convert the bearing from Grid to Magnetic – GMS
• set the Magnetic bearing at the index line
• rotate the entire compass (and your body) so that the N (red) end of the needle aligns with the orienting arrow
• the direction of travel arrow shows the way to move.

A handrail is a natural or man-made linear feature which assists in navigation. Examples are tracks, sharp-topped spurs or ridges, fence lines, creeks, cliff lines. Creek lines are not always easy going, but it may be possible to travel parallel, just out of the denser scrub.

A feature past your intended destination that lets you know you have gone too far. If you miss the intended destination, the catching feature will assist in guiding you back to your destination.

A point near your objective, easily identified on both map and on the ground, used to guide you to your intended destination. For example, you are wanting to reach a hut in a forest. You identify a nearby creek junction and navigate to that. Once there, the hut will be much closer and easier to find. As another example, after setting your compass bearing to your destination, look on the skyline in the same direction for a distinct feature (eg. hill or saddle) and walk towards it.

Intentionally aiming to the left or right of your intended destination to a nearby linear feature (handrail), so you have a known direction to turn once the handrail is reached. For example, if you are heading on a compass bearing directly for the cars on a road, you may arrive at the road but miss the cars. You would not know which direction to turn to reach the cars. If you intentionally set your compass bearing to the left of the cars, you could confidently turn right on reaching the road.

• If watch set to daylight savings, convert it to standard time
• When South of the Tropic of Capricorn, hold the watch with 12 pointing to the sun (check by ensuring that the shadow of a vertical stick falls along the 12 axis)
• NORTH is found by bisecting the angle between 12 and the hour hand.

William Naismith was a Scottish mountaineer and in 1892 developed a time estimation formula for distance on a route in varying conditions. There are many variations, but let’s keep it simple.

“Naismith’s Rule – for an average walker with a medium pack, allow

• 1 hour for every 4km of easy going; 3km of easy scrambling; and 1½km of very rough country, deep sand, soft snow or thick bush
• add 1 hour for every 500m up, and 1 hour for every 1000m down.

For very fit and experienced walkers reduce the total time by one third, and for larger, less fit or less experienced groups, this rule may be optimistic.” (taken from Bushwalking and Ski Touring Leadership, Handbook of the Bushwalking and Mountaincraft Training Advisory Board Inc, 3rd edn, 2000).

(taken from Finding Your Way in the Bush by George Carter, Walk Secretary, Canberra Bushwalking Club, rev Apr 1993)

Adjust using other factors

• Group spread – the larger the party, the slower the trip. Everyone walks at a different preferred pace and has different capacities and fitness. No two walkers will go behind a tree at the same time!
• Add extra time for stops – water breaks, morning tea and lunch, sightseeing.
• Multi-day trip – slower carrying an overnight pack compared to a day pack
• Age – don’t I know it
• Local knowledge of conditions – it’s easier to walk country after a bushfire compared to rampant regrowth a couple of years later. Some off-track walking in Namadgi National Park is less than 1km/hr.

Navigating with a digital device will give you an exact bearing. “What’s the bearing to the next waypoint?” can be answered, after a quick glance at your device, with “It’s n degrees magnetic”. And the compass in the GNSS (eg. GPS handheld, watch) will always show the bearing from your current position to the destination. Modern, 3-axis compasses in such devices will show the correct bearing even if you are stationary.

It’s more difficult to measure a bearing on a map and translate it to your compass, or sight a bearing using your compass. So the answer might be “It’s about n degrees magnetic”.

Does an imprecise bearing matter? Will you end up missing your objective?

Horizontal deviation (lateral drift) increases with distance. Eg. for 4° difference in bearings at 500m deviation will be 35m and at 1km deviation will be 70m.So be as accurate as you can in determining a bearing and keep the distance to next aiming point relatively short.

Lateral drift

Diagram from The Backpacker’s Field Manual by Rick Curtis.

On the diagram above, the actual bearing from Start to Destination is 338°M. If one member in the party set their compass at 336°M and another member set theirs at 340°M, and the distance from Start to Destination was 500m, they would end up 35m apart.

Lateral drift = dist(Start-Dest)*tan(bearing diff)

eg. 1° diff @ 1km = 17.5m; 2° diff @ 500m = 17.5m; 4° diff @ 500m = 35m

1. The easiest way to precipitate an incident is to split the party. Be very careful when extreme circumstances require the party to split.
2. Party members should walk as a group. Before you become visually separated, call out so that a regrouping can occur.
3. A ‘tail end Charlie’ is normally appointed, particularly for a large group. Other party members should always be in front of them. If someone needs to stop (eg. to ‘find a tree’), the rest of the party should move on a few tens of metres, stop and wait.
4. You just can’t afford to look where you place each and every step. Gaiters will provide some protection from snakes if you accidently tread on one and give you extra confidence when you can’t see your footfall.
5. Scrub gloves (eg. gardening gloves) will give you extra confidence and speed when ‘breast-stroking’ through scrub or swinging by tree trunks. Will also protect your hands from scratches.
6. Eye protection (eg. sun glasses, clear protective glasses) is useful.
7. Keep well back from the walker in front of you. If you get slapped in the face by a bush, you’re too close. Even more so with walking poles.
8. If your walk leader allows participants to walk at their own pace on tracks and you are ahead, stop at every track junction or prominent feature so the party can regroup and set off again in the correct direction.
9. Don’t regroup like a caterpillar! When the head of a caterpillar stops and the tail catches up, the head takes off again. Give the slower walkers at the tail a chance for a breather, just like the faster walkers at the head have had.
10. When rock scrambling, 4 points of contact can be safest. Move one at a time of hands, feet and butt!
11. Step over small logs across your path. Don’t stand on top of them. They’re slippery when wet or frosty.
12. Use the risers and treads of steps. If you walk the more regular slope immediately beside the steps, you’ll aid erosion and the earlier demise of the steps.
13. If at all possible, walk through shallow water. Don’t widen the track by walking the drier sides. In fact, water will often lie on firmer ground.
14. If a gate is locked and has no step through, climb over closest to the hinged end. This will put less strain on the gate and it will waggle less. If a gate can be unlocked, leave it as you found it.

I posed the following question to the NSW Spatial Services Hub:

The North point diagram on the 8727-3S Tuggeranong 1:25000 topo printed map (copyright 2003) includes “Grid-Magnetic Angle 13.7 degrees. Magnetic North value is correct for 2003 and moves easterly by less than 0.01 degree per annum.”

The North point diagram on the currently available e-topo map from SIX, 2017 edition, includes “Magnetic North is 13.6 degrees East of Grid North.”

Why is the G-M angle for 2017 less than that for 2003, when MN moves slightly eastward?

I’m not being pedantic. I teach map and compass navigation at the Canberra Bushwalking Club and would like to know the definitive answer.

Within days I received the following answer:

The simple answer is that the underlying Australian Geomagnetic Reference Field model (AGRF) has improved over time.

The model, administered by Geoscience Australia, is updated every 5 years.
While the magnetic declination drift over time is likely to be easterly in each model (at your location), the underlying value may have improved in value and accuracy.

You can compare the most recent model (2020): https://geomagnetism.ga.gov.au/agrf-calculations/agrf-model.

… with some previous models:

e.g. 2010 model https://www.ga.gov.au/ausgeonews/ausgeonews201006/geomagnetic.jsp

e.g. 2005 model http://www.ga.gov.au/ausgeonews/ausgeonews200503/geomag.jsp

For easy access to the latest magnetic declination at any location, you may consider this calculator:

https://geomagnetism.ga.gov.au/agrf-calculations/agrf-form

Screen shot below shows the most recent AGRF2020.
For your interest, I recommend a review of similar graphics at all of the links above.

AGRF2020 Declination at Epoch 2020.0

There are many sources of topographic and schematic maps. Find them on the internet.

The organisation responsible for producing 1:25000 topographic maps of primary use to bushwalkers/hikers is the NSW Department of Land and Property Information. It provides a Spacial Information eXchange (SIX) tool for accessing Georeferenced PDF Topographic Maps. Customers are permitted to print their own hard copy of a Topographic GeoPDF Map.

Go to e-Topo. Zoom and pan to the area of interest. Click on a location in the area of interest. The map name appears as the Select a map: entry. Click Download PDF.

Alternatively, go to the Spacial Map Viewer. Zoom and pan to the area of interest. From the Layer List Widget, turn on GeoPDF Download. Click on a location in the area of interest. Click on the TOPOGRAPHIC MAP icon to download it. You can then save the GeoPDF.

Open the map, using a pdf viewer such as Adobe Acrobat DC.

Pan and zoom as required.

To control what part of the map is to be printed on an A4 page, do Edit, Take a Snapshot. Define an area of maximum 7 * 5 or 5 * 7 grid squares.

Access the Acrobat Print function. Click the Custom Scale: radio button. Leave the % at 100. Click Print.

Check that the width and height of a map square on the printed map segment is 4cm. Use the 1:25k scale on your baseplate compass.

An idea is to laminate the A4 page in a home laminator pouch.

The downloaded PDF could be taken to a print service facility (eg. OfficeWorks) and printed in A3. I haven’t tried this.

I understand that CalTopo can produce the same result. I have not tried it.

I used to print A4 segments by scanning a printed map. Not much good if you don’t own the printed map, or your version is out of date.

The basis for this information bite comes from Printing A4 NSW topographic maps from your printer, on the Hiking Sydney website. This source was brought to my attention by a post by Todd Dzur on the A.C.T Hikers Facebook page, in answer to a question from Cam West. Comments by Beat Oppikofer also encouraged me to examine this topic.

Grade 1 – No bushwalking experience required. Flat even surface with no steps or steep sections. Suitable for wheelchair users who have someone to assist them. Walks no greater than 5km.

Grade 2 – No bushwalking experience required. The track is hardened or compacted surface and may have a gentle hill section or sections and occasional steps. Walks no greater than 10km.

Grade 3 – Suitable for most ages and fitness levels. Some bushwalking experience recommended. Tracks may have short steep hill sections a rough surface and many steps. Walks up to 20km.

Grade 4 – Bushwalking experience recommended. Tracks may be long, rough and very steep. Directional signage may be limited.

Grade 5 – Very experienced bushwalkers with specialised skills, including navigation and emergency first aid. Tracks are likely to be very rough, very steep and unmarked. Walks may be more than 20km.

The grades are developed from the following criteria.

Distance

1. up to 5km
2. up to 10km
3. up to 20km

Grades 4 and 5 may be over 20km, but distance isn’t used for grading at these levels.

Gradient

1. Flat
2. Gentle hills
3. Short steep hills
4. Very steep
5. Very steep and difficult.

Quality of track

1. Well-formed track
2. Formed track
3. Formed track, some obstacles
4. Rough track, many obstacles
5. Rough unformed track.

Quality of markings

Grades 1 and 2 pretty obvious

Grade 3 – signs might be a bit more spread out

Grade 4 – sparse signage

Grade 5 –     no signage.

Steps

1. No steps
2. Occasional steps
3. Many steps.

NPWS adds extra considerations.

Experience Required

Grades 1 and 2 – no experience needed

Grade 3 – some experience

Grade 4 – bushwalking experience recommended

Grade 5 – a lot of bushwalking experience required.

Time

Grade 1 and 2 – high and low end estimates

Grades 3, 4 and 5 – estimated hours or days.

At one extreme is an autocratic style, where no party member is given any choice. At the other is laissez-faire, anything goes and it’s difficult for a decision to be made.

In between telling others what to do and doing nothing, might be political, evaluative, participative and democratic styles (Bushwalking and Ski Touring Leadership, Handbook of the Bushwalking and Mountaincraft Training Advisory Board Inc, 3rd edn, 2000)

Start with a style that you’re comfortable with, readily take on board suggestions and always be willing to change. Remember, we walk for the enjoyment of all.