31 March 2010
TASMANIA 15th APRIL 2007 - COMPASS NAVIGATION ^
Having just completed a 9 day 97 kilometre hike from the tallest waterfall in Tasmania at Meander Falls and travelling cross country to Lake St. Clair we passed near to the IRONSTONE range which we discovered to be magnetic in nature and severely affecting our standard orientation compass. In the Meander region we found that compass readings varied up to 20 degrees when two compasses were only 10 metres apart. Near large rocks this was greater but on eroded flat areas; consisting of the same bedrock; this was minimal. It is suggested that Global Compasses be used as they are efficient at dealing with high magnetic dipping. Beyond Long Tarn near Mount Jerusalem this effect became negligible and readings coincided with use of GPS.
The highlight of this leg of the journey were views from an un-named peak located 1.75km from the centre of Lake Eros on a bearing of 242 degrees true North. From there we could view Mount Jerusalem in the N.E. all the way to the jagged Du Cane range laying to our west. The exact coordinates on the 1:25,000 "DUCANE" map series are: 55G 04 29364/53 55248. The area is untracked sub alpine scrub of moderate density but with some sections of Phagus (Australia's only deciduous tree) making forward progress very slow.
The final section of our journey was 16km along the CUVIER track on the west side of lake St. Clair. The area south of lake Petrach is a muddy and water logged section of button grass plain. Although a marked track, it is advised by the park rangers that only experienced walkers use this path. In some sections the mud is knee deep and the trail can fade easily. North of the lake is some wonderful steep forest walking, the thick canopy opening at times to reveal the scraggy peak of Mount Byron.
Our day walk to MOUNT RUFUS; lying at an altitude of 1416 metre; was an 18km circular loop starting at Lake St.Clair, which unlike the western Central Plateaux was free-walking along a rocky track with only stunted subalpine vegetation. The views extend dramatically to FRENCHMAN'S CAP, the King william Ranges and afford clear views of the mountain's of the OVERLAND TRAIL. This walk is highly recommended by myself. A fast unladen hiker can achieve this in 4.50 hrs although the track markers suggest 7 hrs.
PHOTO: CENTRAL PLATEAU ON A PREVIOUS AUTUMN HIKE, WITH UNSEASONAL SNOW.
***The Silva EXPEDITION-54 compass (as pictured above) consists of standard orienteering baseplate but with a sighting prism located near the West cardinal point and is accurate to half a degree. It will not work in areas such as the Ironstone ranges. Alternatively,The Silva Voyager 8010 is a fully damped compass which will accomodate severe needle dipping
Posted by marcus micheaux (aust)