Tag Archives: gps

Bushwalking Navigation | How to make a customised, calibrated map from an .ecw map file.

Do you have a Mac computer? Want to know how to use a ecw map file to produce a customised, calibrated, topographic map? Don’t know which software to use? Don’t want to use a Windows emulator? Not sure which map datum to use?

UPDATE (Tuesday 3 July): advice on calibrating TOPOMaps version 2 ecw files  modified

The following discussion relates exclusively to two highly regarded Mac applications that I, and millions of other Mac users, have been using for what seems like a lifetime. Both are fully supported with user forums, have a prompt response to enquiries, are low cost for what you are getting, and are actively being updated by developers who have a love for Macs. These applications are

It is of course possible to use OziExplorer on a Windows computer or emulate a Windows machine on your Mac, but these are a poor substitute for powerful, user friendly software, running natively on a Mac.

I assume that you are using the latest version of Graphic Converter (GC) (there is a trial period so you can fully test it before purchasing) and have it running in 32 bit mode. You can do this by control clicking on the GC file icon, selecting the Get Info box and then checking the  “Open in 32 bit mode” check box if this choice is available [ see diagram] NB  ecw files won’t open in 64 bit mode and you will get an error message if you try to do so.

MacGPS Pro doesn’t have a demo version, but it does have a 30 day money-back guarantee.

iOS Applications

MacGPS Pro also has an iPhone/iPad/iTouch version iHikeGPS which is  suitable for New Zealanders and North Americans, due to the availability of free maps. Australians miss out as our maps have to be purchased.

Bit Map (Australian design) allows uploading and viewing of custom maps made using the technique outlined below, using an iPad or iPhone, which is something that few other apps can do. While its plotting features are not as complete as MacGPS Pro, it does allow the plotting of waypoints and routes,  or uploading from an OS X mapping application such as MacGPS Pro via iTunes. Like MacGPS Pro it allows live viewing of your current position using the built in GPS.

Disclaimer: I have no relationship with the  developers of the software discussed above.

For my review of Bit Map click this link.


IMPORTANT: If you have a small (a few map tiles only) .ecw file and the accompanying .map geo-referencing file is in the same  folder, then MacGPS Pro will open and calibrate the ecw file, as soon as your drop it on the MacGPS icon, without any further action on your part. If you don’t have the corresponding .map file then you will need to calibrate the newly imported ecw file as in Step 7.

    1.    Drag  the  ecw file from your CD to the GC icon, and dialogue box below will pop up. Select a slightly bigger area than you want by dragging the square corners of the large box [see diagram below] and then position the box by dragging from the middle of the box. Select Downsample.”None”, then click OK. HINT: It doesn’t need to be accurate at this stage. Just make sure the area of interest is inside the selected area.

  2.    Select the part of the image you want by using the selection tool (the dashed square, second line on the right) [see diagram] from the toolbox (bring to forefront by clicking command-K)  and save as (file/save as) a pict file, which is the native MacGPS Pro format. Make sure you have checked the radio button Save Selection Only.[see diagram below]  [Steps: name file, select file format ie PICT, check save selection only]

 3.    Open Mac GPS Pro, set the units (file/unit choices) to the appropriate datum,
which should correspond to the map datum of the paper maps you have or will be purchasing.

If you intend printing labelled maps directly from MacGPSPro as pdfs, then I would suggest you set to GDA94, as this is most likely to be compatible with the maps of others in your group.

 eg GDA94, UTM, kilometres, metres magnetic, click OK. [see diagram below]

    4.    Drag the cropped pict  file from your Finder onto the MacGPS Pro icon.
    5.    A dialogue box will open and ask you to “Set the map’s Datum  and Projection type”  [see diagram below] Select GDA94 for most discs recent mapping discs and Transverse Mercator. Click OK

    6.    It will then pop up a “Standard Coordinates for the Map” dialogue box. Enter the grid zone (see image)

and check the ‘Store calibration in PICT file” box, then OK [see diagram below]

    7.    You will then have a “Click known Points to Calibrate Map ” dialogue box pop up. Check the map datum is set to the same as your hard copy maps before proceeding. [see diagram below]

Complete this for any four easily recognized features (eg trig point, windmill)  located near the four corners of the map, using a hard copy of the map to provide the 7 digit eastings [eg 0262600] and northings [eg 6553800]. Click DONE.

HINT: Make sure you have zoomed in as far as you can, without the map becoming too pixelated, using the zoom icon top right, to increase your accuracy.
VERY IMPORTANT: If you are using an ecw file from a TOPOMaps version 2 disc (South Australian), then be aware that the grid lines on the ecw file are those of the AGD84 datum, as the file has been scanned from pre-94 maps. If however, you open these maps in OziExplorer you will find that the associated .map file (found on the disc) has calibrated the maps as GDA94 hence the disc markings.

The Instructions file on the disc ( who reads the instructions?!) say

The map image displayed (in OziExplorer) has been recalibrated to the Geocentric Datum of Australia 1994 (GDA94). The Easting and Northing readouts for any point at the cursor position will in GDA (94) coordinates.

Please Note:
The map images were scanned from AMG 84 based maps. Therefore, if the cursor is placed at the intersection of two grid lines, the coordinate readout will not correspond to the values of those grid lines. Future map editions will display a grid pattern based on the GDA94 datum and therefore the readout will then correspond to the grid values. See also p25

The warning above is very important, if you normally use grid line intersections as your calibration points, as this will result in inaccurate calibration, with the whole map displaced 100-200m. If you use recognized topographic features this problem doesn’t exist.

HINT: To speed up the process in case you need to start over again, keep a record by printing a copy of the map and annotating it with the four corner grid references which you previously entered. If MacGPS Pro won’t let you click the DONE button it is probably because you made a mistake entering the GR and will need to start again, or perhaps you have failed to select a point on the map, to register the grid reference.

The Ultimate Goal

Remember that the goal of calibrating a map, plotting waypoints and joining them to form a route using MacGPS Pro is so that you can transfer them to your GPS and use your GPS to find your location relative to these waypoints, on either a purchased map or one printed using the software. For this reason, the map datum set in your GPS MUST match the paper map you are carrying.

My next few posts will explain how to export your data from MacGPS Pro to your GPS, overlay the calibrated map you have produced on Google Earth to help you visualize the terrain and get the UTM coordinates from Google Earth by overlaying with UTM grid.

Visit some of my other related navigation posts

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


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.

Challenging Mountain Day Walks in the UK | Three of the Best

Visiting the United Kingdom (UK) and in particular Wales, England, or Scotland for a holiday? Like to spend a day(s) in the mountains, surrounded by beautiful alpine scenery? Like a challenge? Have some experience walking in alpine terrains, scrambling over rocks and the ability to navigate? ….then look no further!

I’ve just come back from climbing three of the most popular mountains in the United Kingdom (UK) in one of the wettest months (April) on record. These are not huge mountains (950 – 1350m) and on a good day, can be tackled as day walks of 5-8 hours from the nearest car park, following footpads and tracks, but the difficulties should not be underestimated, and it is for good reasons that all of these walks are recommended for experienced walkers.

The level of difficulty is highly weather dependent; on a sunny, clear day, the challenge is mainly fitness, but on a cold, windy, and foggy day with a thick layer of snow over the track, ice on the rocks and rain, sleet or snow falling, the challenges can be life threatening. I had the misfortune to experience all of these on each of my walks: Mt Snowdon 1085m (Snowdonia, Wales), Mt Helvellyn, 949m, (Lake District, England) and Ben Nevis,1343m, (Fort William, Scotland).

As with all walking in mountainous terrain, you need to go prepared for all weathers; sun glasses for bright sunny times, beanie and gloves for cold days, waterproof jacket and over pants for wet times, map,  compass and GPS for foggy weather, poles for snow covered slopes and down jacket and bivy bag in case you have to spend the night out. Forget just one of these and you could be in real trouble.

Normally April /May in the UK would be spring days with just a cap of snow above 700m, but there is no such thing as a normal day in the mountains. I found that strong winds, snow, hail and rain tested my preparedness and fortunately did not show me lacking. Only the week before I arrived, a lone walker had slid off Mt Snowdon, one of the most popular walks in Wales. I could understand how this could happen, as while the terrain is not difficult on a fine day, in adverse weather, the challenges are enormous.

Pyg Track, Causeway, Llyn Llydaw

The key to survival in adverse weather is to make a risk assessment early in the walk and decide whether to turn back or take a lower route before you have committed yourself. On Mt Snowdon, 1085m, I decided to turn back, probably too late, after having completed most of Crib Goch, the most difficult part. This was a difficult decision, as I knew the easy part was not much further on and if only the fog would clear I would be able to see my route. The fog never cleared and my route became deeper and deeper in snow as I progressed. I contemplated dropping off the ridge to find the lower track, but remembered that this was not advised and  a trial descent for a fifty metres only reinforced this. Too slippery, too steep and plunging into the unknown.

Apparently many of those dying on the mountain are actually quite experienced technically but make poor decisions about when to turn back. I was glad I did not become one of those statistics.

Striding Ridge, Lake District, England

Mt Helvellyn, 949m, along with Striding Ridge, in the lake district of England was my second walk a few days later and I could not believe that it was not long before I was again walking in snow, hail and fog. Fortunately the terrain was less demanding and I did not feel the need to turn back. Every so often, a break in the clouds would show the route and the twenty or so walkers I could see ahead and behind, and I was reassured. I was glad I had my walking poles with me, as the snow covered rocks were quite slippery and a fall was quite possible. I knew that the way back along Swirral Edge, was not too difficult when I had lunch with a mountain biker at the top. I can only suppose he carried his bike for much of the way as he was quite exhausted.

Ben Nevis, 1343m, ( The Ben to locals) is the highest mountain in the UK and as such, subject to some of the worst weather. Locals joke that you can expect all four seasons in any one day, and even a blizzard thrown in for good luck. So bad is the weather usually, that the last few hundred metres has cairns every 50 m, so those walking in fog don’t fall off the side. Of course this only works if you can see the next cairn, or follow the track which I couldn’t, due to deep snow and fog. Fortunately the map has a compass bearings to follow in white-out, and while helpful, success depends on being able to estimate distances in fog, a tricky skill at the best of times. I was quite nervous as I approached the top!

I came back to Australia with a deep respect for these “lowly” mountains which have tested many a walker in the past and found too many of them lacking.

  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.

    iPhone Apps for Bushwalkers Revisited

    It’s over a year since I began reviewing iPhone apps for bushwalkers. During this time I have tried hundreds and found that I only use a few regularly.

    While there are hundreds of iPhone apps useful to bushwalkers and growing every day, what you personally find useful is determined by your past experience, the type of walking you do, your interests,  and your willingness to be dependent on high tech devices.

    After trying most, I regulary use only a few of these. On bushwalks, my choice will vary as it is dependent upon on the duration of my walk, and hence how important it is to save battery power,  and upon how much non-walking time I will have available.

    My iPhone Apps

    Navigation: Bit Map, Declination, Maps, Google Earth, Compass
    Field Guides: Good Reader, BooksApp, Kindle, Aus. Birds (Morecomb), Field Guide Fauna Museum Victoria, Bird in Hand, WhatBirdNZ, Wikipanion, MyEnviro, FrogLog
    Bushcraft / Survival : KnotsGuide, SASSurvival, Knots, GoneTrekking
    Camp Food: Jamie Oliver’s Recipes, Poh’s Kitchen, Nigella Quick (….LOL)
    Fitness: Walkmeter, Beat Monitor, Cadence, iHandy Level
    Weather: Pkt Weather, Rainspotting, Clouds, iBarometer, ShralpTide, Clouds,WeatherNZ
    Travel: Frequent Flyer, Webjet, Plane Finder, Lonely Planet, Trip Advisor
    Astronomy: Star walk, Star Guide
    NZ: WeatherNZ, WhatBirdNZ, SnowReports
    Photography: Flickr
    Medical: Elastoplast, MediProfiles, St John NZ

    Disclaimer: Navigation using your iPhone always needs to be backed up with a compass, map and a dedicated GPS. 

    I have written reviews of many of these iPhone apps previously in this blog, several articles about how to use iPhone apps in general while bushwalking, and detailed articles which focus upon iPhone apps for navigation, fitness and NZ.


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

    Bushwalking Navigation | Using Creek Lines in Arid Environments

    Ever wondered why it is so easy to get lost following a creek in an arid environment? What precautions can you take? Why is it more difficult to navigate uphill than downhill?

    I have just come back from 4 days in the Vulkathunha-Gammon Ranges, over 700 km north of Adelaide where rainfall averages less than 20 mm per month with most of it falling during summer as the tail end of monsoons in the north west of Australia sweep down into northern South Australia and temperatures rise into the mid to high 30s. This has been one of the best start to the bushwalking season for many years and there are large numbers of full waterholes in the creek beds, lots of weed infestations and even a mouse plague.

    Walking is usually via dry rocky creeks beds, as the ridges are often steep, rugged and exposed. Sometimes the creeks are full of native vegetation such as paperbarks (Melaleuca) and flood debris which makes movement with a full pack difficult.

    Invariably navigation is a challenge, as few, if any, of the creeks have flowing water to help decide which way is downstream and it is difficult to distinguish major tributaries from mere gully’s. Often creek beds are hundreds of metres wide and may have islands in the middle, which can give the impression of a creek intersection, leading to miscounting.

    Creek navigation involves

    • starting from a known location (use your GPS)
    • deciding how far away the next creek intersection will be and whether it will be on the left or right
    • calculating your walking speed and using elapsed time as a guide to when the next intersection should occur
    • counting creek intersections as you go
    • checking map to ground as you walk for obvious features such a gorges, cliffs, bends in the creek and stopping if they don’t appear in the correct sequence and place
    • using your compass to check the direction of each creek at each intersection with that expected from the map
    • checking for debris against tree trunks and trickling creeks to decide which way the creek is flowing
    • checking your location frequently with your GPS, even if you think you know where you are, as often parallel creek beds, can appear to be very similar. 
    • deciding on a catching feature so you don’t go too far or a handrail you can follow (see below for glossary)

    If you have a GPS, then set up a route linking waypoints you have pre-determined at each creek intersection (decision point). This will give you distance to the next intersection, time to next intersection and bearing, but has severe limitations if the creek bed is very windy as all directions are “as the crow flies”. The GPS should never be relied upon without confirmation from map to ground, especially in narrow gorges where reception can be poor.

    Uphill navigation following creek lines is always more difficult than downhill, as there always at least two uphill choices at each intersection but coming downhill, it is unlikely that you would decide to go back uphill at the intersection, knowing that the main creek must be going downhill.

    Other Similar Posts

    Bushwalking Navigation | A Glossary of Frequently Used Terms 
    Bushwalking Navigation

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

    Bushwalking Navigation | A Glossary of Frequently Used Terms

    Have you ever wondered what SOG and VMG mean in the context of navigation? What is a breadcrumb trail? What is the difference between a backbearing and a resection? What are waypoints and how do they differ from a  grid reference?

    Glossary Terms Description
    .kml The KML file specifies a set of features (place marks, images, polygons, 3D models, textual descriptions, etc.) for display in Google Earth, Maps and Mobile, or any other 3D Earth browser (geobrowser) implementing the KML encoding. Each place always has a longitude and a latitude. KML files are very often distributed in KMZ files, which are zipped files with a .kmz extension.
    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 point A feature, which is near but much easier to find than your objective.
    Back Bearing Used to see if you have deviated from the intended path. Face starting point. Check that south end of needle is centred on mark.
    Bearing or Course A bearing is the angle between a line connecting two points and a north-south line.
    Breadcrumb trail  A track is a compilation of samples or “breadcrumbs” taken over a period of time.
    Calibration The process of inputting the grid references of known points, usually the four corners of a map.
    Catching feature Prominent features which are beyond your
    objective but
    can act as safety net. A bearing on prominent feature at
    90 ° to direction of travel can be used.
    Coordinates In 3D latitude, longitude and elevation
    Easting, Northing The terms easting and northing are geographic Cartesian coordinates for a point. Easting refers to the eastward-measured distance (or the x-coordinate), while northing refers to the northward-measured distance (or the y-coordinate). (Wikipedia)
    Escape Route 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.
    Grid Reference Numerical grid references consist of an even number of digits. Eastings are given before Northings. Thus in a 6 digit grid reference 123456, the Easting component is 123 and the Northing component is 456. (Wikipedia)
    Handrail 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.
    Heading Compass heading or course measured from true or magnetic north.
    Map Datum The horizontal datum is the model used to measure positions on the earth. A specific point on the earth can have substantially
    different coordinates, depending on the datum used to make the measurement.
    Naismiths Rule A rule of thumb that helps in the planning of a walking or hiking expedition by calculating how long it will take to walk the route including ascents. (Wikipedia)
    Pacing A pace is the distance between each right foot hitting ground. For 1.8m person, with
    pack, ≈ 1.5m ie 660 paces to 1km.
    POI Points of Interest. Often downloaded in advance of a walk.
    Raster Map Made up of a grid of pixels also known as bitmap
    Resection 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 °
    Route Two or more waypoints
    Route Card The planned route is broken down into a series of legs, each of which begins and ends at a clearly defined feature, and which can be followed on a single compass bearing. In addition, distances, height gains
    and losses and times calculated using Naismith’s rule are included.(Wikipedia)
    SOG Speed over ground. The speed at which you are moving over the surface of the earth.
    Topographic Map A type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines.
    Track A track is a compilation of samples or “breadcrumbs” taken over a period of time. (MotionX GPS)
    Transect Bearing Useful to locate exact position on a handrail., by identifying a prominent feature and drawing a back bearing on the map to intersect the handrail.
    UTM Universal Transverse Mercator coordinate system; a grid-based method of mapping locations on the surface of the Earth
    Vector map Scaleable, small file size, where lines are specified by coordinates not pixels; not raster or bitmap.
    VMG Velocity made good. Effective speed at which you are approaching your waypoint.
    Waypoint Sets of coordinates which identify a point in space, often given as a grid reference.

    Related postings

    Bushwalking Navigation

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    Bushwalking Navigation | How to Choose the Best iPhone GPS App

    Which navigation features do bushwalkers need?  Which features do a selection of the iPhone GPS apps have? How do you decide which of the iPhone navigation apps suits you best?

     There are thousands of navigation apps for the iPhone, but only a small number are designed for non-motorists. From these I have selected just a few supporting the iPhone’s built in GPS and compass sensors which could be suitable for the needs of bushwalkers, trampers and hikers. I was going to eliminate those that only use lat/long for locations or don’t have metric units, but there are many friends who read these blogsand who live in the USA.

    You should make your choice based upon your intended use, not on the number of features available, as often compromises need to be made by developers to fit in more features. Better to have a few key features fully developed and easy to use, than a multitude of features which are very limited in their capabilities.  Key deciding factors will be whether you wish to share your bushwalking with others via the web, whether you want to plan your hike using complementary desktop software and sync with your iPhone later and whether you really only want to view maps and need a limited set of GPS features.

    Free versions of apps are often available which allow you to test features before purchasing and this option should be fully explored. Beware of seemingly low priced apps that require you to purchase each additional map or pay to use their integrated website. Some apps may initially seem expensive, but come with a full quota of high quality 1:50K topo maps preloaded.

    A few of the most frequently mentioned iPhone navigation apps in bushwalking/hiking /tramping circles are

    Which are the features that the ideal bushwalk navigation app could possess?

    Disclaimer: The accuracy of the data in the table below is limited by the quality of the information supplied by the developer and, if critical, should be checked by emailing Support at the address above.

    Features MapApp NZ Mud Map Bit Map Motion X GPS Memory Map
    Offline Map Viewer, with fast scrolling and zooming
    Ability to load, tile and show maps in a large number of formats


    • #5
    Display current position centred on map and share in realtime
    • No


    Display position coordinates in UTM and lat / long
    • #4
    Support metric units
    Show tracklog (route taken) and allow trackback.
    Create and edit waypoints and link to form routes
    Import/export waypoints, tracks and routes (multi format)
    Share routes and waypoints via email, the web or Twitter
    View SOG, VMG, distance to and bearing to waypoint.
    Show current speed, max speed and time to destination
    Use compass to give current heading (course)
    Display total ascent /descent and gradient graphs for a route
    Live speed and altitude graphs.
    Show sunrise / sunset and tide times
    Placename index for searching
    Voice announcements of user specified data
    Desktop software which syncs with iPhone
    Geotag waypoint and integrate photos taken along route
    Background track logging with low battery consumption
    Multitask with audio and phone
    Search | GoTo
    Links from POI to Wikipedia
    1 Limited access to topo maps for Australian bushwalking areas
    2 Topo50 NZ maps included in purchase price. One app for north island and one for south island, containing all NZ 50K maps
    3 Topo50 maps for NZ are available free of charge but you need to buy additional maps for Australia eg iTOPO 1:250,000 maps (4×4 and Outback touring) • Westprint Outback maps (4×4 and Outback touring) • Gregory’s touring maps (4×4 and Outback touring) • Melway Street Directories• VicMap  1:25K
    4 Lat / long only hence useless for bushwalkers but may be great for hikers.
    5 Can acquire maps, .kml, .kmz, zip, by email. Can use OziExplorer  maps or scanned and calibrated maps
    6 Limited access to USGS maps. Additional maps for a fee.Time limited Demo period on most maps to see if it is the map you want to buy and keep.


    Unfortunately for trampers and bushwalkers there does not seem to be any ideal GPS app for the iPhone which also allows the use of high resolution uploaded maps. Either the maps available are of insufficient quality or if they are suitable then the GPS has limited features.

    • Bit Map allows the upload of high quality user supplied maps but has only a basic set of GPS features.
    • MotionX GPS has superb GPS features, equivalent of any dedicated GPS, but seems to lack suitable maps for Australian bushwalkers
    • MapApp NZ has superb free maps preloaded but, other than the ability to show current location, has  no other GPS features.
    • Memory Map has limited access to Australian maps but has a good range of GPS features.

    Related Postings

    Bushwalking Navigation | A Glossary of Frequently Used Terms 
    iPhone Navigation and Map Viewer App Review | Bit Map 3 by Nixanz
    Review: The iPhone’s Navigation Potential for Bushwalkers and Hikers 
    Bushwalking Navigation
    iPhone Apps

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    Bushwalking Navigation | GPS vs Paper Map vs iPhone

    Which is better for navigation, your GPS or a paper map? What are the strengths and weaknesses of each? Do you need to carry both? Are there any alternatives to a dedicated GPS and map?

    In bushwalking circles there are always vigorous debates about which is best, a dedicated GPS or a topo map?  This is sometimes generational with older members preferring the map, with which they are familiar, and younger bushwalkers preferring the GPS. To some degree the dictum “each to their own” applies in bushwalking as a walker who doesn’t understand how their GPS works is a danger to themselves and others in their group and would be much safer navigating with a map .

    Of course the argument is not that simple, as many modern GPSs now contains maps which can be viewed and overlain with waypoints and your current position. You can now take your digital maps with you when you walk. Fortunately the opposing viewpoints are not exclusive as it is possible and in my view essential to take both, especially when bushwalking in difficult terrain.

    I love to walk “thumbing ” my laminated map which allows me to get the “big picture” around me, orientate myself using distant features and anticipate what’s around the next corner. I do however use my GPS to check my location at each stop or at critical “decision points” such as creek junctions, waterholes or ridge descents.

    Paper maps have some disadvantages:

    • they get damaged easily, especially at the folds, and require laminating
    • they are cumbersome in a strong wind if you have to open them
    • multiple maps are often needed and changing from one to another in your map case is often difficult
    • they require special storage facilities at home
    • the printing is often too small to see without  reading glasses.

    HINT: try laminating your maps in A4 sections, with maps both front and back, which will fit individually into your map case.

    Paper maps do however still have many advantages:

    • they allow you to orientate yourself using distant features
    • they can’t go flat as they don’t rely upon batteries
    • they may be more waterproof than your GPS, especially if you are using a “smartphone”
    • they are cheaper in the short term 
    • they work even under a dense forest canopy trees or in narrow gorges.

    A GPS has several advantages over paper maps:

    • it can compactly store large amounts of data, plotted on a large desktop computer screen, and then uploaded via a cable, infrared, bluetooth or wireless.
    • if the GPS has a large colour screen and sufficient memory then you can store a large number of maps, which can be scrolled and zoomed. You need never go off the map as they will be seamlessly “stitched together”.
    • it allows you to determine your location quickly with high accuracy and reliability, subject to several limitations: not under a dense forest canopy trees or in narrow gorges.
    • if you have a large touch screen (eg iPhone) then you will be able to effortlessly scroll and zoom, so that your reading glasses are never needed.

    Of course there are many features they share, such as the ability to determine location. Experienced map users will be able to lay a compass on their map and do a resection using prominent features to find their current location. Even better they will have “thumbed” the marked route on their map from the beginning and never become lost!

    Alternatives to a dedicated GPS

    There are alternatives to a dedicated GPS such as a  smartphone, many of which have large colour touch screens and excellent built-in GPS’s. The iPhone is a good example of such a phone, and as most bushwalkers should be carrying a mobile phone with them anyway, this can serve as a good back up for those who prefer to use maps but don’t want the expense of purchasing a dedicated GPS. There are several excellent mapping apps (applications) which are very easy to use on the iPhone and while they don’t match a dedicated GPS for versatility, they only cost a few dollars.

    The iPhone does however have two major limitations: battery life and lack of waterprooofness, but both of these can be overcome with solar panels and waterproof covers.

    Read more about the uses of the iPhone for bushwalkers

    Related Posts

    Can my GPS replace My Map?
    Why am I Lost When I Have a GPS?
    How to Keep your iPhone Charged in the Outdoors 
    Bushwalking Navigation

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    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.