Birdsville Track Blaze Tree - SA

This Blaze tree was blazed around 1952 as part of the National Mapping programme.

Here are the details :


Natmap Survey Marks

By 1962 the geodetic survey of Australia had been underway for some ten years. In a paper First Order Angular Control (Johnson, 1962) that year National Mapping’s Senior Geodetic Surveyor H.A. (Bill) Johnson stated:…“There is no doubt that, without proper supervision, the first aspect of a survey to suffer will be its marking. Remote or awkward stations, which should be the best and most prominently marked of all for future users, because of their very difficult or cost of access, are usually the poorest marked.
This Division [National Mapping] has tried to make a special point of its marking, with due regard to getting materials into distant areas, permanence, ready recognition and future use by other survey authorities and to carrying out daylight observations.
In very flat country, near Mataranka to Newcastle Waters, and across the Nullarbor Plain, 20' and 30' galvanized windmill stands have been erected on concrete emplacements, and after use as instrument stands, have been left as future marks. (Note 20’ is the pre-metric annotation meaning 20 feet).
Cairns have been erected, however, wherever possible, with centre poles and vanes - the most stable shape being 7'-8' diameter, 5'-6' high, pudding-shaped, with 11' pole and four 3' x 2' vanes…11' steel poles, internally steel-strutted, are now used.
To avoid the heavy and unnecessary labour of dismantling these carefully constructed monuments, and to enable other observers to sight to them at any time, instrument standpoints are chosen eccentrically [away from the centre] and usually form one of three recovery marks emplaced.
Most surveyors can quote examples, not only of thoughtless or careless damage, and loss of marks, but also of deliberate, wanton destruction of them.
Some of these new geodetic marks could remain unvisited for generations, but within 5 or 10 years, most future visits will be by helicopter.
In all cases, such visits are likely to be more expensive than the initial ones establishing the stations, and it is hoped no time will be lost in finding any such sought for mark by future users”.
This philosophy has meant that many cairns and later beacons still exist today some 50 years later. Not only do these marks exist but apart from natural weathering have not deteriorated significantly. The condition of beacons found along the Canning Stock Route is shown here http://xnatmap.org/adnm/docs/trig/trig.htm
and one in the Tanami Desert here
http://xnatmap.org/adnm/docs/recolls/mng56.htm

Survey marks of earlier years are less visible. Being generally wooden posts they have succumbed to ants, rot, fire etc. However, where the survey mark has been cut (blazed) into the living wood of a tree these marks can survive provided of course drought, fire, clearing etc does not eliminate the tree.

National Mapping’s first surveys to provide control for aerial photography photomaps were a series of Astro-fixes. Dave Hocking’s paper here
http://xnatmap.org/adnm/ops/prog/astro_new.pdf
covers these surveys and lists the identifiers used in blazing a tree at the site of each Astro-fix. For each Astro-fix a Station Summary was prepared which summarised location and coordinates. Until recently only one such summary existed that for NM H 1 the first Astro-fix done by Dave on 21 May 1948 near the Frewena Road House (now gone from the Barkley Highway, NT). A copy of this summary is at the end of Dave’s paper.
In 1984 the Adelaide Advertiser of Thursday, 1 November reportedhttp://xnatmap.org/adnm/docs/drh_advertiser.pdf
the finding of another of Dave’s Astro-fixes NM H 173 near Innamincka, SA. The date of inscription was 19 July 1952.

A Coolabah tree stump (add my photo) inscribed NM H 116 has been on display in Canberra. The stump came from Birundudu Station in the central west of the Northern Territory and was cut down in 1970 to allow the building of a new homestead. NM H 116 was another of Dave’s Astro-fix sites circa 1950s but the station manager had been unaware of its importance for many years.
Recent interest in another of Dave’s Astro-fixes NM H 168 north of Etadunna on the Birdsville track, however, has bought some more information to light. The complete set of Astro-fix summaries was destroyed as not relevant many years ago but copies of Astro-fixes in South Australia still exist. Thanks to Chris Jordan and his team at the Lands Services Group, Department of Planning, Transport and Infrastructure, SA, the station summaries for NM H 173 and NM H 168 have been made available.
(show SS images)

Of particular interest is that the summary shows the coordinates for NM H 168 as 28° 31’ 24” S, 138° 42’ 06” E as computed from the observations of 13 June 1952. The GPS coordinates from the supplied photo are 28°31’ 17” S, 138° 42’ 14” E giving a discrepancy in latitude of 7” and in longitude 8”. As a rough guide 1” is about 30m so the difference in position 60 years apart in time is around 250m. Factor into that a shift of some 100m when the GPS datum was adopted and the difference is reduced to around 150m. To put that into perspective it is the fence to fence distance across the Melbourne Cricket Ground (apologies for the Melbourne-centricity).

In the 1960s Natmap was carrying out Astro-fixes in SA for the R502 program…….





References

Johnson, H.A. (1962) First Order Angular Control, Presented, Australian Survey Congress (6th : Adelaide).