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GPS navigation is very well suited for bushwalking in the Perth region of Western Australia. Due to the relatively light or open eucalypt forest conditions and mainly gentle terrain in this region the GPS unit is able to maintain good satellite coverage and tracking in almost all areas, with the result that good navigation accuracy should be achieved. Location accuracy is often as good as 5 metres.
|Modern GPS units can generally maintain accurate position fixes even under denser tree canopy. In my experience (using Garmin's basic eTrex unit) misleading readings have been rare, as verified by directly comparing downloads of the actual 'tracks' (recorded while walking) with the intended routes. Misleading readings could occur however on steep hillsides (due to signal reflections) and reduced accuracy will occur if less than 4 satellites are in view of the receiver or if they are all in line or in a tight grouping. Those situations are unusual however and the receiver will indicate if the signal is weak and navigation accuracy is poor. Clouds and weather conditions do NOT significantly affect accuracy.|
Commonsense dictates that we should always have a map and magnetic compass with us when going cross-country bushwalking and know how to use both. The map should be used in conjunction with your GPS. You should have at least sufficient map-reading skills to know where you are on the map and in relation to the surrounding terrain. Knowing where you are on the map also allows greater flexibility to vary the route away from a straight line to the next waypoint (e.g. to avoid thick scrub or to visit features of interest seen off the direct line while walking). In this region it is really a matter of personal preference whether you use your magnetic compass routinely in conjunction with the GPS or as back-up in an emergency (e.g. in the event of misleading or confusing GPS signals, flat batteries and no spares, or if the GPS unit gets damaged or lost).
Personally I prefer to keep the compass as emergency back-up only; using the GPS direction pointer arrow on its own (in 'Go To' mode) is easier and quite sufficient. However, if you are to rely mainly on the GPS in this way you need to be aware that you have to be moving for the GPS pointer arrow to correctly point toward the destination. Generally you will probably know from your map and surroundings the approximate direction to start walking in. After only a few walking paces the GPS direction arrow should indicate the correct direction to the destination waypoint. While continuing to walk you can then readily make any necessary adjustment to your walking direction. If you have no idea which direction to start walking in, simply move off in any direction and then similarly make the direction adjustment so that your walking direction matches the direction indicated by the pointer arrow.
If you prefer to use a magnetic compass to maintain your direction between waypoints, then you can obtain from the GPS data display the bearing from your current location to the destination waypoint. Transfer this bearing to your compass and then use the compass to establish your walking direction in the traditional way. One advantage of using a compass routinely between waypoints is that it will save on batteries which could be a key consideration on longer walks. A disadvantage is that using the compass encourages less interesting 'straight-line' walking between waypoints and detracts from the great flexibility that the GPS offers to vary the route away from a straight line and still find the destination.
Whichever navigation style you adopt, never forget that the basic GPS unit is NOT a compass. i.e. The GPS direction pointer arrow does NOT show you which way to move while you are standing still. (Also see 'Before starting to walk' below).
If you have a scanner and one of the GPS mapping software packages you will be able to quickly create your own walk routes and maps in six or seven simple steps as follows (OR in place of Step 1 & possibly Step 2 you can use map images already available for the region on DVD or CD or your software may be able to access GoogleEarth, Google Maps, and/or NearMap; or for U.S. users to import Maptech topo maps etc):
Create a Map Image file (e.g. .bmp, .jpg, .png) by scanning the portion of an existing map which covers the area of your planned walk.
Calibrate the Map Image to the known Grid Coordinates using GPS mapping software (e.g. GARtrip, GPSUtility, OziExplorer -see External GPS links). Ensure you set the correct Map Datum and Projection.
Set Waypoints on the Calibrated Map at locations you may wish to include on your chosen Route. This creates a Waypoint Listing. Alternatively, you can import waypoints from existing listings such as provided on each walk page of WalkGPS as free, downloadable waypoint listings in Garmin PCX5 file format (also suitable for direct serial upload to a GPS unit, after first unzipping and loading into a freeware program such as g7towin). Also see WalkGPS Maps, Waypoints & Tracks page which provides downloadable PCX5, GPX and Google Earth (KMZ) files for all walks, plus notes on how to import into mapping software such as OziExplorer (after first loading and calibrating a map) or to upload via cable to your GPS unit.
Create an intended Route by selecting Waypoints from the Listing in a suitable sequence for your walk.
Print off a hard copy of your Calibrated Map showing the Waypoint locations and your planned Route. (See separate note below on the potential for uploading of custom map information to your GPS unit.)
Upload (transfer) the Waypoints and Route to your GPS unit from your PC through an Interface Cable. This eliminates the very slow and very frustrating task of manually inputting Waypoints and Routes into your GPS.
Save your walked 'Track' - When you are on your walk you will no doubt at times decide to vary your path from the planned Route. For that reason it is very useful while walking to record and save your actual 'Track' in your GPS. You can then download it into your PC after your walk to compare with your original planned Route and make any changes that you might prefer if you plan to walk in the area again.
Buying your first GPS unit - The main brands of hand-held receivers offer a large number of models with prices ranging from around A$135 for a basic or entry-level unit to over A$1000 for units with greater loadable memory size, built-in map databases and larger screens. Be wary of over-investing in capability and features that you may not need or use. The entry-level units are excellent value for money and are quite adequate for most bushwalking purposes. They are also generally smaller, lighter and simplest to use, and generally give longer battery life. The more expensive hand-held units usually include map databases, but most walkers will still want to carry good paper topo. maps due to the small screen size of the units and the limitations of some of the available databases. Ironically, entry level units may have better outdoor legibility than more upmarket units with touch-screens.
NOTE: This site, WalkGPS, is non-sponsored and is not an agent or retailer for any brands of GPS units.
Using your own maps - Your own walk maps (and those on WalkGPS) created from scanned base maps and loaded as image files into GPS mapping software cannot be directly uploaded to your GPS unit. A typical hand-held unit does not import or support maps as image files, but requires a database of digital (GIS) map information to be able to display the map. Waypoints, routes and tracks can be readily uploaded, but if you want to prepare custom map information that is uploadable to your unit you will need to use a database program, or Garmin Custom Maps which provides a very simple process for georeferencing of the map image files in GoogleEarth and then uploading the kmz file to certain Garmin handheld units and/or importing to Garmin BaseCamp freeware for walk planning or review. OziExplorer GPS mapping software can upload waypoints, routes and tracks, but not maps, to a handheld GPS receiver.
Many GPS receivers suitable for bushwalking have the capability to import maps (e.g. Garmin eTrex 20, eTrex30, Montana 650 & Oregon series & Magellan Triton series), but you will need digital topographic map data ('vector' maps, not 'raster') for your area at suitable scale (or alternatively use the Garmin Custom Maps process). Australia-wide vector contour map coverage includes: “OZtopo V4”, “GPS TopoPLUS Australia 5m”, suitable for use with Garmin BaseCamp (and Mapsource legacy) software and some hand-held Garmin GPS receivers; and “DiscoverAus Streets & Tracks Topo”, suitable for some of Magellan’s eXplorist and Triton series receivers.
Also see maps suitable for GPS receivers.
Using Google Earth - Google Earth does not claim to provide positional accuracy of GIS or survey quality. Google Earth is very useful for picking 'rough' waypoints and routes, but don't expect the data to have the same accuracy you would obtain from GPS field-derived data or accurate survey-quality maps. e.g. In the Perth region abrupt shifts of up to 13-16m occasionally occur along stitch lines between adjacent imagery runs and extend over several kilometres. Position shifts up to about 20m between the imagery and the roads overlay and GPS data (tracks and waypoints) are also common. If the apparent shift in the GPS data matches the shift in the road overlay, which is most often the case, you can measure that shift, then apply it as a correction to location coordinates read directly from the Google Earth imagery.
To import GPS data into Google Earth, the most economical and fail-safe way is to first convert the data into Google Earth KMZ format (e.g. using GPS Visualiser) which can then be opened in Google Earth. Google Earth often has problems correctly opening GPX files.
A set of waypoints and track (really a pseudo-track) for a new route can also be very easily created and exported from Google Earth via the following steps: i) create a new folder in "My Places"; then, ii) locate Google Earth Placemarks and a Path on the imagery; iii) save the folder as a kmz (zipped kml) or kml file; iv) open the kml file in GPS mapping software or convert it to a GPX file (e.g. via GPS Visualiser) for direct upload to a GPS unit. The Google Earth Placemarks and Path become the Waypoints and Track in the GPX file. Be mindful that the Google Earth data is likely to be less accurate than the actual GPS data recorded on a walk.
Datum - The walk maps on this site (WalkGPS) use a UTM position format and a 1 km grid. Select the UTM (Universal Transverse Mercator) System in your GPS unit to determine your position rather than Latitude and Longitude. The UTM system (with its Easting and Northing grid coordinates in metres) is more practical for field use than using Lats. and Longs. (in Degrees, Minutes and Seconds or Decimal Degrees) and helps obtain more accurate location measurements off a map. Select the datum setting in your receiver to match the datum of your hard-copy map (e.g. AGD66, GDA94 or WGS84) if you wish to read-off and hand-plot coordinates for locations from your GPS unit onto your map; - but be aware if you upload coordinates by cable from your PC to a GPS unit, they will always be uploaded assuming the datum is WGS84 (the standard GPS default datum).
Before starting to walk - It is very important to leave the GPS unit on for a few minutes (depending on your unit, up to about 5 minutes) at the start point of your walk, before you start walking. This gives the receiver time to lock on to as many satellites as possible and to get an accurate starting location. If you do this the receiver will be able to maintain accurate location information during the walk and even if you turn the receiver off temporarily (e.g. at a rest point) it will be able to quickly and accurately find your current location (usually in 15-30 seconds). If you don't give the receiver time to lock on at the start point it may not be able to maintain a lock onto sufficient number of satellites and will then not give accurate location information during your walk.
New waypoints - One of the great benefits of using GPS is the ability to accurately record the position of interesting features that you come across on your walk that you may want to be able to revisit in the future. This is especially useful for locating small or subtle features that would have been very difficult to find again using traditional compass navigation. When marking a feature as a new waypoint it is useful to give it an appropriate short descriptive name (instead of a number) to help remember in the future what the feature was.
Cross-country walking - When a route is 'off-track' (i.e. when it is cross-country, not along an existing track, 'trail', or 'path'), the easiest walking between each pair of waypoints is often not exactly along the straight line that is shown on the map. When walking off-track, you need to be prepared to pick your own sensible route to the next waypoint by looking ahead and varying from the direct line to bypass local obstacles such as patches of thicker vegetation or unnecessary multiple stream crossings.
GPS 'track' files versus bushwalking tracks - New GPS users may be confused by the use of the term 'track': In GPS terminology a 'track' means nothing more than a plot of a series of map points which have each been recorded (logged) by a GPS receiver or have been opened from an uploaded 'track' file. A GPS 'track' does NOT have the same narrower meaning of a traditional walking 'track' (or trail). A GPS track may in fact be mostly or partly cross-country (i.e. 'off-track'!) as in the case of many of the walks on WalkGPS (which are also provided as GPS 'track' files on the Maps, Waypoints & Tracks page).
Battery life - Battery life for the Garmin eTrex (which uses two AA batteries) is only sufficient in normal mode for about 10-12 hours of continuous operation, but this can be extended to about 22 hours in 'Battery Save' mode. Use rechargeable batteries.
Lanyard or carabiner - Always keep your GPS unit securely looped onto your belt or clothing by a lanyard or carabiner. The hand-held units are small and very easy to leave behind at a rest stop unless attached to you!
If you haven't used GPS navigation before, you will find that getting started is easy. The manual that comes with your GPS unit will probably be sufficient, but you can also obtain additional information from a number of websites :
Using GPS (user guides etc)
GPS Receivers for bushwalking
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This page was last updated : 17 May, 2013
Site authored by David Osborne. Photographs and text are copyright © 2003-2013 David Osborne.