Tag Archives: route_card

Bushwalking Navigation | Documenting Your Route Plan

How do you document a route plan? How can you use Google Earth to check the route and save pics of critical navigational decision points? How do you use mapping software to plot and export the waypoints to your GPS, print the route and elevation graph? How can you annotate your map pdfs? How do you protect your maps from the weather?

This post is part 2 of  Bushwalking Navigation | A Route Plan Workflow

Getting the “big picture”

The first step in planning any trip is to read guide books, talk to other bushwalkers and search  bushwalking forums, websites and blogs to discover which routes are popular. 

Once you have decided on your intended route you will need to check water availability, weather conditions, locate existing tracks, property boundaries and permitted camping spots.  Don’t forget to check photographic websites such as Flickr, which give a good idea of popular sites and the scenery to be expected.

Next study the terrain to work out your likely speed, keeping in mind height gains and losses, the density of vegetation, the amount and difficulty of any off-track walking, and the presence of waterfalls in creek lines, which may need to be bypassed.  Once you know these you will be able decide how far apart your camping spots can be and determine each day’s starting and finishing times.

I have discussed many of these navigation techniques and route plan design in previous posts (21) and won’t go further into detail now.

Finding a Map

You should never rely solely upon a GPS for critical navigational decisions and for this reason bushwalkers should always carry topographic maps covering the route, and the surrounding countryside just in case you get off track. These can be purchased from a local map or outdoors shop, and are usually available at 1:50,000 scale but sometimes at 1:25,000, which provide more detail, for popular areas.

If you are walking the Heysen Trail in South Australia, there are two excellent guide books (Northern and Southern), with log books readily available available which include maps that are adequate for most walkers. The CFS also publishes (Mapland) excellent map books, and these too are available from map and outdoor shops. Many downloadable walking brochures for our parks are available from the Department of Environment’s Parks SA website.

With digital maps readily available, many people are using mapping software to select just the relevant parts of maps and to enlarge these beyond the 1:50K scale than is usually available in printed maps, making it easier to see the contour and creek lines. If you are lucky enough to live in NZ, you can download 1:50,000 maps free of charge and even Australia has 1:250,000 maps for free download from Geoscience which are useful for getting the big picture and planning access roads.

Using Mapping Software

My apologies to Windows users for the following Mac centric discussion. 

As a MacBook Pro user I have used MacGPS Pro mapping software for many years to import my scanned maps, plot my routes and export the waypoints to my GPS. A print out of the waypoints file is an essential record of each waypoint’s  name, grid reference, comments, and elevation

One big advantage of mapping software is that it is possible to enlarge the map on screen to locate the exact position of known waypoints  or to determine the grid reference to 7 figure accuracy of any point you can see. Once you have decided on your waypoints you can rapidly link these to form a route, calculating distances and bearings automatically by dragging from point to point, and plotting a route elevation graph by selecting the route single click. The elevation graph is useful for estimating time to be taken.

From MacGPS Pro

The disadvantage of using a Macintosh is that without a Windows emulator, such as Bootcamp, and an installed version of Windows, OziExplorer software doesn’t work.

For older Macs (not using intel cpu) use Virtual PC or for new OS X Macs with the Intel CPU use either Bootcamp or emulation software called VirtualBox or ParallelsVirtualBox (Sun Microsystems Inc.) is free for personal use. It works in OS X on Intel Macs. (OziExplorer – Running OziExplorer on a MAC or Linux Computer )

There is a way to overcome this and that is to import the maps from the disc in .ecw format into a graphics program such as Graphic Converter, select the relevant part and then save as a PICT or TIFF file.  Some of the .ecw image files are small enough to import directly into a mapping program such as MacGPS Pro.

Often the .ecw image file will be accompanied by a matching .map calibration file and providing you keep it in the same folder as the ecw file, you can then import into MacGPS Pro and automatically calibrate the map. You could of course still do it the old way which was to scan and process a hard copy of the map.

Assuming there is no matching .map file available, calibrating a digital map using MacGPS Pro requires that you first rotate the map (using GraphicConverter) so the northing gridlines are horizontal and then enter the full 7 figure grid references of four widely spread points, usually near the corners of your map.

Top Left:  Easting 0263000 Northing 6540000, Grid Zone 54J, AGD94

From MacGPS Pro

You must also enter the UTM grid zone and know the projection and map datum eg I am using a portion of the Oraparinna map for a forthcoming trip

From MacGPS Pro

NB UTM Grid Zones is SA are either 52 (far west), 53 (west) or 54 (central and east)

Annotating your pdfs

Annotated portion of Oraparinna map

There are several programs (I use Skim) that allow you to annotate a pdf. This is particularly useful as it allows you to add grid references to the margins of your map (NB MacGPS Pro has a menu item “View/Gridlines” which does this automatically for you) and add notes about the route. Most programs allow you to add arrows showing routes and highlights. Once you have done this, you can export as a pdf and if you have the full version of Acrobat take advantage of its ability to reduce the file size significantly, to as much as a tenth.

Using Google Earth to Plan a Route

Google Earth can be used to visualize the route, finding 4WD tracks, checking whether creek lines are heavily vegetated and to see if ridges would be easier going. Cattle, goat and sheep tracks converging on a creek line probably indicates a waterhole, spring or a shallow crossing. Rainwater tanks, galvanised iron shelters, windmills and bores can sometimes be seen in Google Earth, even if they are not marked on the map.

Flinders Ranges: Google Earth screen capture

Simply import your .kml file showing your waypoints and then zoom in and tilt to see your route in 3D. Use a screen capture program, such as  Snapz Pro X, to capture pics of significant parts of the route, with your waypoints shown. Save these to your iPhone, camera or print, for later reference while on the walk.

NB I can never get my GPS waypoints to exactly match those in Google Earth, as I assume it uses a different map datum

Protecting your maps

One of the advantages of printing your maps from pdfs is that you can print them in A4 format which means they can either be laminated back-to-back or placed in a map case without the need for folding.

Other relevant posts

The Bushwalking Navigation series

Other Resources

Department of Environment’s Parks SA website
Bushwalk Australia Forum
Friends of the Heysen Trail

  Creative Commons LicenseThis article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.


Bushwalking Navigation | How far have I walked?

Want to know how far you have walked or how far you still have to go? Which  tools can use to find this info? What pre-walk planning should you have done? What should you be doing while you are walking? Can your GPS be relied upon to give this information?

 Part 1 of this article was published separately but has now been merged with Part 2

Knowing how far you have walked can determine whether you have a safe trip. Without knowing the distance you have walked, and the time it has taken, you can’t estimate how long it will take you to get to your camp site and whether you will make it before nightfall.

The best way is to “thumb” your map as you walk along, so you know where you are at all times and use this information, along with your route plan, your average speed and time since starting, to work out how far you have walked. Your GPS can give you a good guide too, but over long distances your GPS can be significantly inaccurate and should not be relied upon as your sole source of this information, especially if you are moving slowly in difficult terrain.

Before you can work out how far you have walked, either you or your GPS need two bits of essential information

  1. where you started
  2. where you are now

The first should be easy, but the second can be much more difficult. You can make it easier for yourself by doing some preparation before you leave home and again at the start point (trailhead for those from NA).

Silva Map Measurer Plus

Before you leave home

  • purchase or download (lucky NZanders!) a map and guidebook if available.
  • use navigation software (smartphone or PC*) to explore your digital map, measure distances, select routes and waypoints
  • view the terrain in Google Earth or Google maps, select your waypoints, route and measure distances
  • enter way points into your GPS and link them as a route, using the software or just manually
  • measure distances using a map measurer or piece of cotton or a ruler, depending on whether the track is straight or windy
  • prepare a route plan
  • mark your map with your route and waypoints

* I have used MacGPS Pro for the last 10-15 years on my Mac.

    At the beginning of your walk
    • locate yourself on the map
    • check the time and start you stopwatch/timer
    • mark the start waypoint on your GPS and set it to navigate to your  next planned stop
    • reset the Trip Odometer on your GPS
    • reset your pedometer if you are carrying one

    PS don’t forget to adjust the time and date on your camera as well, as it is good to be able to match photos with your GPS location when you get back home.

    While you are walking

    • “thumb” your map, reading map-to-ground as you walk along, “ticking off” prominent features as you walk along
    • use your GPS, and known features, to work out your average speed and use your stopwatch, which you started at the beginning of the leg, to estimate how far you have walked, based on the average speed
    • continually check that the terrain matches where you should be on the map based on your average speed and time you have been walking, less breaks. This is a very difficult skill to learn and needs continual practice as it is very easy to miss a creek junction or mistake a knoll. Carry a map even on an easy day walk and practise.

    When you reach your objective

    • your objective should be a prominent feature which is on your map and your route plan. Use navigation techniques such as aiming off, handrails, catching features and attack points to help you locate the feature.
    • use your GPS to check your location, making sure you are using the correct map datum
    • use your route plan to look-up the distance, which you hopefully measured using one of the devices listed above before you set off
    • use your GPS’s Trip Odometer to tell you how far you have walked (subject to inaccuracies: read below)

    Why my GPS can’t measure distance travelled accurately.

    Your GPS trip odometer should only be used as a backup in determining distance, not as your primary device, as it is unable to accurately determine distance travelled in typical off track walking terrain, as occurs when you are walking along a windy creek track with tree cover, overhanging cliffs and the odd waterfall to climb. For most use on open tracks the accuracy will be adequate but for a 10 km walk leg through difficult terrain, the inaccuracy could be as much as 10-25% of  the true distance.(Source: Garmin Forums)

    One of the reasons for this is that the GPS adds the distances, as the “crow flys”, between the points it has saved, to the trip odometer and these will usually be slightly shorter that the actual distance you walked, especially if you have changed the data logging from the default which is usually once per second (1hz) to something less frequent. The only exception to this will be if you are walking in a straight line when it should be able to measure with 100% accuracy. The inaccuracy will be further increased if you make frequent stops, turn frequently or walk slowly, say less than 3.5 km/hr, so that the GPS doesn’t know you are walking. Walking up a steep incline can also produce inaccuracies, as the GPS only measures horizontal distances.

    The accuracy will be increased by increasing the data logging rate  eg 1Hz (once a second) to 5Hz. The problem with this is that your battery may not last as long and when you reach the internal memory limit it may start deleting the oldest.

    From the Garmin Forums: Distance of Trip odometer not the same than distance of Track

    When you walk (or drive), the GPS is constantly doing calculations based on where you are this instant compared to where you were on the previous location reading so it “knows” which direction you are traveling and how fast you are traveling.

    At each of these calculations, it also calculates the distance traveled and adds that to the Trip Odometer.

    Most GPS units do these calculations approximately once each second. You do not travel very far in one second, even in a motor vehicle traveling at the speed limit, so each of these calculated distances will be fairly accurate. That means when you add them all up, as the Trip Odometer is doing, the total distance in the Trip Odometer at the end of the trip will be fairly accurate.

    One thing that will affect the accuracy of the Trip Odometer when you are hiking is if you are not moving fast enough for the GPS to detect that you are moving. That could cause little pieces of travel to not get added into the Trip Odometer and the distance it reports to be shorter than reality.

    Track files are different. If you save the track log to a file, it always prunes the log to 500 track points, regardless how many points there are in the raw log file. If your driving or hiking was not in a long straight line, you will “lose” distance when pruning the points. That is, if you walked in a curve that originally had 20 points marked and the curve gets pruned to, say, 3 or 8 points to describe it in the track file, you will not get the full distance of the curve calculated in the track.

    That is because the calculations of distance in the track file all assume that the distance between each recorded point is a straight line. If you describe a curve with fewer points it will always look like the curve covers less distance.

    If you transfer the raw track log file to Mapsource or Basecamp, you should get all of the track points and that should cause less of a difference between the track and the related Trip Odometer reading.

    Further reading:

    Bushwalking Navigation | Using Topo50 Maps (LINZ) for Tramping in New Zealand
    Bushwalking Navigation | How to Choose the Best iPhone GPS App
    Bushwalking Navigation: The Importance of Using the Correct Geodetic Map Datum.
    Bushwalking Navigation | A Route Plan Workflow
    Silva Map Measurer Plus
    Bushwalking Photography Workflow | Share the Best of a Group’s Photos Using iPhoto

    Read more Navigation posts

      Creative Commons License This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

    Bushwalking Navigation | A Route Plan Workflow

    How should I begin my route plan for a bushwalk? What resources are there available on the web? Are there any time savers? How do I  keep others in my group informed and allow active participation in the decision making? How do I take my route plan with me and share it with others in my group? Who should I tell about my route plan? Do I need an escape plan?


    A route plan is an essential part of any walk for three reasons; firstly as a way of easily checking whether the walk you have planned is too easy or too difficult in the time you have allowed, secondly as a way of improving the safety of your walk by sharing the route with others in your group, police, park rangers and friends and finally as a practical navigation aid.

    Fortunately, few of us need to navigate in a whiteout, but if we do, a route plan which gives the distance and bearing of each leg and has chosen prominent waypoints as end points is an essential safety component.

    An Example of  a Route Plan for Skiing and Climbing

    Despite the importance of the route plan as a planning requirement, route plans are made to be broken and can become a liability if they are adhered to despite the weather, condition of the group and terrain. A good leader must be willing to vary the route plan to suit the circumstances!

    A good route plan depends on the quality of the waypoints it uses, the selection of which needs to be based on sound navigational techniques some of which are listed  below. A waypoint which can only be found with a GPS is useless if your GPS fails and it will!.

    Aiming Off

    • Used to find an objective on a feature which is straight eg river, mountain ridge, road
      • Deliberately aim to strike the feature 10 ° to right or left of feature and then turn along feature to reach objective (also called Stefansson method or intentional error)

      Attack Points:

      • A feature which is near but much easier to find than your objective.

      Catching Features:

      • Prominent features which are beyond your objective but can act as safety net. 
      • A bearing on prominent feature at 90 deg to direction of travel can be used.


      • Definite features which are roughly aligned with direction of travel and  which make navigation easier.
      • Don’t use creeks or gullies but may run parallel to them.

      In Poor Visibility:

      • Stick to well defined features or proceed from one well defined feature to another. 
      • Navigator 3-4 places from front, with party in single file.
      • In snow, use a cord 50m long and have scout sweep in an arc until next pole found.


      • A pace is the distance between each right foot hitting ground.
      • For 1.8m person, with pack, ≈ 1.5m ie 660 paces to 1km.


      • Keep navigation legs short, moving from one identifiable point to the next, even if this involves a detour.
      • Align straight edge of compass with 2 features, with arrow pointing in the intended direction.
      • Rotate bezel until parallel lines on its base align with grid lines.
      • To correct for magnetic deviation, rotate bezel clockwise (MGA: grid to magnetic subtract).
      • Set out in direction of arrow with needle centred on its mark.

      Back Bearings

      • Used to see if you have deviated from the intended path.
      • Face starting point.
      • Check that south end of needle is centred on mark.

      Transect Bearings

      • Useful to locate exact position on a handrail.
      • Identify a feature which is marked on your map then take a bearing on this feature.
      • Convert magnetic to grid by adding the magnetic deviation.
      • Rotate bezel anticlockwise.
      • Place compass on map with arrow on base pointing towards the identifiable feature.
      • Rotate whole compass until the parallel lines of bezel align with grid lines.
      • Draw a line back using the edge of the compass until it intersects the handrail.
      • Choose a feature which is as close as possible to reduce error.


      • Used to describe process of drawing three intersecting transect bearings to find your present location.
      • Select features which are at a maximum angle to each other. eg 120 deg

      Route Planning Software

      As a Mac user, I have only used the excellent program MacGPS Pro which I have had and regularly updated for many years. Australian PC users have OziExplorer which is also excellent and can be run on a Mac very successfully if you install Windows. If you have an iPhone you have other alternatives depending on your country; Australian’s have Bit Map and Memory – Map, New Zealanders Map App NZ and Memory – Map, the British National Geographics Topo Maps. All of these allow you to rapidly plan a route by simply clicking waypoints  which are linked together and can then be uploaded to your GPS.

      The other big advantage of mapping software is that you can zoom in at a magnification that you would need a hand lens to view on your 1:50K topo paper map. With just one click, you have  7 figure eastings and northings for each waypoint along with the map zone.  Distances and bearings, “as the crow flies”, can be measured by two clicks. Route elevations can be plotted with a few clicks.

      Once you have the route planned you can export it as a .kml file which can be loaded into mapping software such as that found on your iPhone, Google maps or Google Earth for others in your group to view. Alternatively you can export the waypoints as a spreadsheet which can be printed as part of your trip intentions form which you will give to your designated emergency contact and to the local ranger or police station or uploaded to Google docs for everyone in your group to view. Uploading to Google docs encourages participation in the planning process and a sharing of ideas.

      Escape Routes

      These are the routes you will take back to safety if anything prevents your progress to your destination. This could be an injury, the weather, too slow progress or physical blocking of your route by a landslide, avalanche, bushfire or flooded river. These should appear on the back of your route plan and be given to everyone who gets your route plan. Their format is identical to that used in your route plan. While some escape routes can be anticipated and planned in advance eg if a river you have to cross is flooded, others such as following an injury can’t easily be planned. Of course, if you have a PLB or a mobile and reception, then in case of life threatening injury you can always call for help rather than follow an escape route.

      Web Resources

      Online Walk Time Calculator: use this online trip calculator to work out your estimated walk times for your route plan, using Naismith’s Rule and Tranter’s corrections for fitness.
      Naismith’s Rule
      Online Route card  From 1st Kirklevington Scouts
            Automatically calculates times based upon inputted speeds and climbs.
      Blank Route Card
      Escape Route Template
      What is a Route Card
      Related Posts

      Online Walk Time Calculator
      Bushwalking Navigation
      Mapping Software

      Creative Commons License This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

      Bushwalking Navigation: The Importance of Using the Correct Geodetic Map Datum.

      Does it matter if your GPS is set to the correct map datum? To which map datum should you set your GPS? Can you compare grid references from an old and new edition of the same map which have different map datums?  How can you convert from one map datum to another? Are the grid references in old guide books correct?

      Setting your GPS and mapping software to the correct datum can make a significant difference to grid references with errors of almost 200m common. While not as important for prominent features, if you are trying to find a spur to descend from a ridge line or a specific creek junction in rugged terrain or a waterhole, accuracy can be critical.

      Both your GPS and mapping software need to be set to match the map datum of your data source which can be found in the legend of the paper map you have scanned, or on the CD label of the digital map you have purchased.  Beware, the first digital edition of TopoMaps for South Australia uses the Australian Map Grid 1984 but more recent versions use GDA94.

      Often when planning a walk you may have obtained the grid references (waypoints) of prominent features  from an old  bushwalking guide. However, unless you know which map datum was used in the guide, then using these may cause navigational errors, if they are inconsistent with your GPS settings. (see below for an example of differences between AGD84 and GDA94 grid references). Many of the bushwalking guides I have were written when AGD66 was being used!

      HINT: if the map was published pre-1984 you can assume that the map datum is AGD66, if its publication date is between 1984 -1994, then its probably AGD84 and if its after 1994 then it’s likely to be GDA94.

      Adrian Heard’s A Walking Guide to the Northern Flinders Ranges was published in 1990, before GDA94 and hence uses the AGD84 datum, which is the same as that used by the Third Edition (1992) 1:50K maps of the Gammon Ranges. If you are using the latest digital maps, they will be GDA94 and hence Heard’s grid references will all need to be adjusted according to the formula

      AGD84 to GDA94  Add 125 m to the Easting  and add 175m to the Northing

      Fortunately converting from one to another is not that difficult, although not a task you would want to do when trying to find a camp site as dusk approaches. Simply open up the setting field of your GPS or mapping software and change to the correct datum, then reread the grid reference. In addition, many older maps give map specific conversions so you can convert to a more recent map datum (see below for an example)

      Map Datums using for the Vulkathunha – Gammon Ranges maps

      The Illinawortina (6737-3, 1:50K, 3rd Edition) map uses the Australian Geodetic Datum 1984 (AGD84) and has a sticker which says that to convert to Geocentric Datum of Australia 1994 (GDA94), add 125m to the easting and 175m to the northing (confirmed by my mapping software). The free Copley (Geoscience 1:250K) map uses map datum GDA94 (more recently adopted).

      Octopus Hill, for comparison purposes, has the following UTM grid references :

      0316970 6624770   visual taken from 50K map which is AGD84
      0317095 6624945   when converted to GDA94
      0316971 6624780   scanned 50K map and mapping software set to AGD84
      0317093 6624958   scanned 50K map and mapping software set to GDA94

      0316748 6624968   Copley 250K map and mapping software set to GDA94

      Observations from data above:

      1. No surprises. The 250K map is not accurate enough for bushwalking navigation, with features up to 350m from their 50K map location.
      2. Using the correct geodectic datum is very important with errors of 125 m possible in eastings and 175m is northings.
      3. The last 5 digits of the GR give Thousands, Hundreds, Tens and Units of metres, so 0316748 differs from 0316970 by 222m. This means that locations on the  250K Copley map can be several hundred metres away from their true location. I have “boldened” the 6 digits usually quoted in grid references.

      Related Postings

      Why am I lost when I have a GPS?
      Bushwalking Navigation 

        Creative Commons License This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

      Bushwalking Workflow | Planning a Bushwalk

      You may have heard the saying that 80 % of the fun of a bushwalk is in the planning, 60% talking about it afterwards and – 40% doing the walk! It’s not quite like that for me, but certainly the planning and the challenge of a new location are the most important components for me.

      I spend hours checking out maps, reading the bushwalking blogs of those who have done the walk before me, talking to people in the outdoors shops that I know, perusing the  walking guides, using Google Earth to see the route in 3D, plotting waypoints using my mapping software and checking out the picture galleries of those who have already done the walk. I like to have the complete picture before I do the walk so there are no surprises. This increases my anticipation and enjoyment.

      Thorough planning enables me to enjoy the scenery, wildlife and plants while I walk, listen to others in my group without having to concentrate on my map too intensely, take lots of photos and generally relax. I could not do this if I hadn’t planned carefully in advance and didn’t have the whole route in my head.

      The first step for me is to choose a new area where I haven’t been before or perhaps an area where I have been before but to which I would like to introduce some friends or extend the walk with a new challenge. I rarely go to the same area twice.

      Steps to planning a successful group walk

      • Decide on the region and time of year, based on your experience as a leader and the weather conditions
      • Gain approval for walk, if necessary
      • Identify relevant maps, walk guides, blogs and review these
      • Prepare a tentative route (use a route card) including escape routes and alternatives in case of unforeseen circumstances
      • Pre-walk the route if possible, entering waypoints as you go into your GPS 
      • Advertise the walk or invite friends, including information such as
        • difficulty level (hazards, weather)
        • duration
        • dates
        • whether it is a qualifying walk for full membership
      Sample Medical Information Sheet
      • Appoint an Assistant Walk Leader, who is compatible with your personality and who complements your skills.
      • Collect information:
        • Medical, contact details, NOK information
        •  Experience levels of potential walkers
        • Special skills of participants (first aid, navigation, photography, plants, history) ?
        • Obtain access permissions, and any Parks permits needed
        • Have a Risk waiver signed by each participant
      • Determine maximum size of group and how you will restrict group size 
      • Review list of possible participants and decide how you will eliminate those with insufficient experience.
      • Arrange Transport and Accommodation
      • Appoint an Emergency Contact person and determine the trigger for contacting police.NB: Some clubs have a designated person.
      • Obtain permits and get access permissions
      • Advise Trip Intentions to relevant authorities
      • Distribute an Information Sheet to participants including
        • Objectives of walk
        • Route card
        • Escape routes (to seek help or cut walk short)
        • Maps
        • Access, permits, hazards, water supplies
        • Transport
        • A few days before, check transport details, weather conditions, park closures, flooded access routes, bushfires in area, water availability and make adjustments, including cancellation if necessary.
        Bushwalking Leadership [SA]

        • Runs comprehensive bushwalk leadership courses from Day Walk to Advanced.
        Let us know before you go (pdf) (Parks and Wildlife SA)
        Trip Intention Form pdf (NSW Police)
        Medical Emergency Information
        A Guide to Better Bushwalking (pdf)  Bushwalking Leadership SA

        • Contains Sample Medical Information Form and Route Card

        A Risk Management Framework (pdf) (The Confederation of Bushwalking Clubs NSW, 2004)

        • Contains Incident Report Form, Risk Waiver Form

        Before You Walk – Essential Bushwalking Guide (Parks and Wildlife Service Tasmania 2009) as pdf

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          This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.