As spring quickly approaches I thought this would be a good time to go over a few navigational basics and explain how they relate to our new walking guides.
In 2000 Australia changed over to GDA94 (Geocentric Datum of Australia), which was defined in 1994 and based on WGS84 (the World Geocentric System developed in 1984 for use with the satellite Global Positioning System). Essentially GDA94 and WGS84 datums are the same for recreational purposes such as bushwalking. Most current-edition Australian maps now use the GDA94 datum (earlier maps were based on the Australian Geodetic Datum systems AGD66 and AGD84). Bushwalkers using the maps in this guide (or downloading our GPS data) should set the datum on their hand-held GPS to GDA94 or (if this is not an available option) to WGS84.
• There are two sets of lines drawn across each map. Those that run north-south are called eastings and those that run east-west are called northings.
• Intersecting eastings and northings form grid squares with each square representing 100 hectares or one square kilometre. The maps in our guides are not created to a set scale so it is important to look carefully at the scale icon and/or the grid to ascertain the distances involved
• Grid north points to the top of the map (when viewed the correct way up).
• In the map/text example, each segment of a described walk is indicated by a location marker showing the distance travelled (in this case 10 and 12.3km) and the name of the location (such as Erskine Falls Carpark). The text reflects this information with the addition of the full grid coordinates as taken directly from the GPS.
• In the map/text example, the two digit grid numbers in the margins of the map correspond to each grid line. These numbers are abbreviated and are underlined (for easy reference) in the GPS grid coordinates.
• In the map/text example, the GPS grid coordinates show the number 54. This is the UTM (Universal Transverse Mercator) zone number (the earth is divided into 60 north-south zones). The letter H indicates the UTM zone designation letter. Together the UTM zone numbers and designation letters provide what is called a Grid Zone Designation. In a nutshell, Victoria (for example) is divided into two zones: 54H (covering the west side of the state and 55H (covering the east side of the state).
How to download GPS tracks
• Many of our described walking trails has been mapped using a hand-held Garmin GPSmap 60CSx device. Each GPS track is available as a free download at osp.com.au in both .gpx and .kmz files.
• If you don’t own a Garmin GPS device, don’t fret. All of our original Garmin .gdb files have been converted to .gpx files (GPS eXchange Format). This popular open format is commonly used to exchange waypoint, route and track data between various brands of GPS devices and mapping software.
• All of our .gpx files have been simplified to under 500 track points for faster downloading.
• Waypoint data is provided on all our .gpx files and will be kept up to date where possible.
• A .kmz file will open in Google Earth just by simply double clicking on it (as long as you have Google Earth installed on your machine). Google Earth also has native support for .gpx files containing GPS data. In Google Earth go to File > Open and navigate to your folder containing the downloaded .gpx file. If you cannot see the .gpx file in your folder try selecting the right file type (All File Types). Open the file.
• Remember that you will need to be running a software program to handle your .gpx files. These programs usually come with your hand-held GPS device. The program we use with came with our Garmin and is called MapSource. Garmin also have free software called BaseCamp. There are many others on the market.
Just a final word of caution. The maps within our walking guides provide a basic overview of each trail, but are not designed to be used in conjunction with a compass, and cannot replace the accuracy of detailed contour maps such as the Vicmap 1:25,000 series. In other words, use a large contour map, carry a compass and/or a GPS and make sure you have a firm understanding of basic navigation. Hand-held receivers have become very affordable in recent years and are increasingly popular among bushwalkers. A GPS user can accurately pin-point a location at any given time. It’s important to note however, that a GPS is only as good as it’s batteries (or fumbling fingers) and that basic map-reading and compass skills are still required.