Bass Strait Triangulation 1952 - 53

In September 1952 the field parties obtaining astronomical control in Queensland and South Australia for 1:250 000 scale mapping were again recalled; this time to observe the triangulation across Bass Strait, the reconnaissance of which had been completed in 1949.

The purpose was two-fold, to provide horizontal control for R.A.N. charting operations in Flinders Island waters and to link the Geodetic Surveys on the mainland with those on Tasmania.

The original reconnaissance had provided for a full triangulation scheme to carry both distances and positions from the mainland to Tasmania. As well as those points on the islands which were finally used, this would have meant siting a point on Curtis Island and on Pyramid Rock if that were possible. Financial considerations precluded the adoption of the full triangulation scheme; the method used was to junction a triangulation network from Victoria with a triangulation network from Tasmania on a single point connection at Deal Island. Distances north of that point would be calculated from the distance of the opening Victoria line, Cape Liptrap  - Mt Fatigue, while south of Deal island would be calculated from the opening Tasmanian line Mt Arnon - Mt Barrow. Azimuth would be carried forward from the Victorian triangulation.

This time Wild T3 theodolites were to be used by the same observers who had completed the Eyre Peninsula scheme during the previous spring. Luckily some time was available for familiarisation with these instruments and the observers spent considerable time practising in Albert Park observing to various church spires. This practice was just what was needed and all observers approached the new task much more at ease. In addition the Wild T3 theodolite was so much easier to use that confidence was immediately inspired.

For horizontal circle settings the circle was broken into 45º segments; settings on the R.O. were:

00º & 180º            90º & 270 º           45º & 225º            135º & 315º

The reading on the micrometer drum with the first setting on 3" was increased by about 15" with each new circle setting. For uniformity of instruction the following definitions were adopted:

Arc: The direction (or directions) observed as the theodolite is ‘swung’

in an arc from the R.O. to each station in turn.

Round: After completing the ‘arc’, change face on the last station

and an ‘arc’ of directions from that station back to the R.O.

is observed; these two ‘arcs’ make one round.

Set: Eight ‘arcs’ of four ‘rounds’ using the above

horizontal circle settings

complete one set.

On this survey it was decided to mean each round, thus the field books show the mean of four rounds as making up the set.

Field Operations

It was decided to complete the scheme in two phases; South Gippsland to Deal Island in November 1952 and Deal Island to Tasmania from January 1953.

First Phase, South Gippsland to Deal Island

Points to be occupied in this phase were the two primary triangulation stations, Cape Liptrap and Mt Fatigue, two secondary stations, Mt Latrobe and Mt Hunter on Wilson’s Promontory, and a new point on Deal Island. The National Mapping observers were E.J. Caspers (Mt Latrobe), P.H. Lennie (Mt Hunter) and R.A. Ford (Deal Island). D.R. Hocking would have the responsibility of deploying the observing team on Mt Latrobe and keeping them supplied.

Owing to the logistics involved in an operation of this size where two points had to be occupied from the sea and considering the very small number of National Mapping personnel available, it was necessary to have assistance. The Victorian Department of Grown Lands and Survey provided two experienced observing teams to occupy the primary stations Cape Liptrap and Mt Fatigue.

The Mt Hunter observing party was taken by a local fisherman across Corner Inlet to the beach at the foot of the mountain; the Deal Island party by the mailman on his normal run from Port Albert. These two parties, each of an observer and booker, were to deploy their equipment without further assistance while the remainder of those available were to assist in establishing the party on the summit of Mt Latrobe, and then keep them supplied.

This was to prove the most difficult task of the survey. The initial climb took some 5 to 6 hours, thick scrub causing trouble in some places. In addition, the weather was cold with rain most of the time the station was occupied; the rain varying from a very heavy to light drizzle which often lasted all day. Towards the end of their stay on the summit, the observer’s tent was badly ripped in a storm and the point had to be evacuated sooner than had originally been intended. They were camped on the summit for about a fortnight in all.

At Mt Fatigue, the ground mark was missing. Under the supervision of the Chief Topographic Surveyor, the point was relocated by resection of a number of lower and similar order points on the surrounding hills. However firstly all these points had to be visited to check beacons and replumb over their station mark where necessary At Mt Fatigue a round of horizontal angles was then read with the Wild T3 theodolite. After calculation it was considered the point was re‑established within a few inches of the original site.

The Victorian Lands Department provided a VHF radio for each observing party; these radios provided almost perfect communications and were probably the main factor in the successful completion of phase one of the work. For those interested in radio equipment of that time, these VHF sets must have been among the very first manufactured in Australia. While the VHF radio was a fairly new technique the power supply of the set was of a pre-war vintage (a six volt car battery input and a rotary-converter to turn this DC Current to the high tension AC current required by the VHF radio).

Observations were all to lights - the quad, Liptrap - Fatigue - Hunter - Latrobe having first priority. The observers on the last three stations were to cut in the lighthouse on Deal Island on an opportunity basis. All observations from Deal Island were to lights, the distance Deal - Fatigue was almost 84 miles. Progress was slow, the mountains on the mainland often being under cloud, alternatively banks of fog in Bass Strait often hid Deal Island. From South Gippsland, Deal Island is quite spectacular, the summit is almost 1000 feet above sea level and from the peak, falls almost as a sheer cliff to the sea.

The station mark on the peak is some 680 feet from the lighthouse which is on a slightly lower peak. It was necessary to measure down through a steep gully and up the other side to the centre of the lighthouse, and also read the required angle to the distant stations so that the calculation of the correction for the eccentric light could be made.

The final task on Deal Island in this phase was to observe sufficient sets of horizontal angles between one of the Victorian stations and Cliffy Island Lighthouse so that a permanent R.O. was available for the next phase.

It was too difficult to re‑supply the party on Mt Hunter so when it had completed its own observing program it had to be withdrawn. As the Mt Latrobe party had already been withdrawn, Mt Fatigue was the only station available as an R.O. for the Cliffy Island observations. As could be expected the long 84 mile sight from Deal Island across foggy Bass Strait to Mt Fatigue caused many delays; also the flashes from the Lighthouse were so short that even when the sighting was good observing was necessarily slow. The observing took about a fortnight and the Deal Island observing party was able to be withdrawn during the first week in December.

The triangular misclosures in the quad, Liptrap ‑ Fatigue - Hunter ‑ Latrobe were reasonable but not quite as good as expected; however the three narrow triangles into Deal Island were particularly good; being under one second. This was pleasing as only National Mapping observers were involved in these observations.

Second Phase, Deal Island to Tasmania

The occupation of Deal Island and the stations on Flinders Island commenced immediately the New Year holiday was over. R.A. Ford was again to be the observer on Deal Island and proceeded there with the mail contractor, while the flight to Flinders Island became National Mapping’s only operation where a vehicle was transported by air. All equipment, including a Land Rover and most of the personnel were taken by Bristol Freighter to Whitemark airstrip on Flinders Island. New 12 volt VHF radios had been purchased and they arrived just in time for this survey.

On Flinders Island with the help of carrying parties, P.H. Lennie and E.J. Caspers occupied Mt Killiecrankie and Brougham Sugarloaf respectively, while D.R. Hocking was taken by the R.A.N survey auxiliary “Jabiru” to Hummock Island. At this time the weather on the mainland was hot and dry; this evidently had an effect on conditions in Bass Strait. To all events conditions for observing immediately the parties were established, were particularly good; the expected difficult connection Deal ‑ Flinders was completed in two or three days thus enabling the evacuation of Deal and Hummock Islands.

The Deal and Hummock Island observing parties were picked up by “Jabiru” and after a very rough trip made rendezvous for the night with the survey sloop “Warrego”, a converted warship as pictured in Figure 1. The Navy was engaged on a charting operation in Flinders Island waters; this was under the command of Commander D.T. Gale. “Warrego” was under the command of Lt Commander Cooper who was second in command of the charting operation. All observing parties were now ready on Flinders Island for movement on an opportunity basis to Babel, Chappell and Cape Barren Islands.

An observing party was then placed on Babel Island by “Warrego” but independent arrangements had to be made for the establishment of a party on Mt Kerford, Cape Barren Island. The property owner, Mr Robinson, agreed to take the party on his own boat and to provide the necessary horse and dray then tractor and horses to transport the survey party and equipment to the base of Mt Kerford. Unfortunately he was not able to leave for Cape Barren Island for some days.

As there was no normal way of advising Mr Robinson when his tractor and horses should be required for the return trip, it war arranged that a smoke signal would be sent at a pre‑arranged time and this worked successfully some 14 days later.

Figure 1: Survey sloop HMAS “Warrego (II)” off Flinders Island

The parties already established completed observing the triangle, Babel ‑ Killiecrankie ‑ Brougham Sugarloaf. The party from Killiecrankie was then landed on Chappell Island by “Jabiru”. However as always seemed to happen in these cases, the weather deteriorated just as the Cape Barren Island observing party arrived at Mt Kerford; observations had to wait the usual weekly cycle for the storm to blow itself out.

Chappell and Babel Islands are mainly composed of sand which is stabilised with tussocks of strong, tough grass. Both islands are mutton bird rookeries and the tussocks are honeycombed with their burrows. Tiger snakes are also numerous; when the observers were on their late afternoon climb to the summit they often disturbed the snakes which immediately disappeared down the burrows. On the return journey in the dark, after completing the night’s observations, the observers often crashed waist deep through the sandy ceilings of the burrows. These trips were quite nerve-wracking; one always visualised suddenly crashing down on top of a snake.

With the completion of all observations north of the line Chappell Island ‑ Mt Kerford, it was all haste to occupy the two necessary stations on the Tasmanian mainland. These were Cape Waterhouse and Mt Cameron which were expected to be the final stations for our observations. Senior Surveyor J. Hunter and an advance party left by air for Hobart and the remainder for Launceston on the 100 foot ketch “Will Watch” which was able to take the Land Rover in its hold.

The advance party was only able to hire two wheel drive utility type Commer vehicles from the Department of Supply, Hobart. Contact was also made with the Tasmanian Department of Lands and Survey; it was found that to link the Bass Strait triangulation with existing surveys, the chain would need to be carried westward to the Launceston area. A reconnaissance diagram showing the stations to be occupied and the observations necessary was supplied.

Another problem which arose at this time was the lack of finance to cover the cost of this extra work. This was the first time that field parties had encountered financial problems; they were to learn it was to be the first of many times, during the succeeding years. Eventually a small amount of money was allotted to complete the survey and the party was told to finish the task with all speed.

On arrival in the Mt Cameron ‑ Cape Waterhouse area it was found that Mt Cameron was to be a solid climb.

The first ascent which involved some clearing to make a track through thick ti‑tree, took close on five hours from the point where the two wheel drive vehicle had to be left. Cape Waterhouse luckily was a “drive on” station. Once again the weather deteriorated just as the Stations were occupied, taking as usual about a week to return to satisfactory observing conditions over the long lines involved. The final observations across water, the quad Chappell Island – Mt Kerford – Cape Waterhouse – Mt Cameron was then completed. This finalised the difficult problem of island occupation and the logistic problems of re-supply, if the observer’s stay was overlong.

The final observing of the Tasmanian chain between the lines Cape Waterhouse ‑ Mt Cameron, and Mt Arnon ‑ Mt Barrow, was frustrated by smoke haze from burning off operations by the local farmers. For a change weather during the day was still; this enabled the smoke to build up to a thick haze by dusk and made the sighting of lights impossible. This time it was a matter of anxiously looking for the stormy weather with the wind and rain to clear the air; then immediately completing the observations before the fires flared again. The weather was certainly nice for camping in a very beautiful and pleasant area but the constant delays were very frustrating.

It was now found that unfortunately the reconnaissance which had been supplied was in error and that stations Slate Quarry (now Turquoise Hill) - Black Sugarloaf were not intervisible. A new reconnaissance had to be made and the observing parties called in to assist with the proving of lines and clearing. The final outcome was that the last quad had to be replaced by a centre point polygon and a new station Mt George had to be established. This further delay again raised the question of finance and eventually it was agreed that the survey could still be completed. Considerable clearing was necessary on both Slate Quarry (see Figure 2) and Mt George which had also to be marked. However the standard was not as good as it might have been due entirely to the lack of time caused by money restrictions.

Figure 2: Clearing lanes at Slate Quarry triangulation Station, northern Tasmania

The observing parties returned to their respective stations and despite further delays caused by smoke haze all observations were completed by late April. The vehicles were returned to Hobart and that portion of the field party returned to Melbourne by air. The remainder with the Land Rover and survey equipment returned to Melbourne by sea on M.V. “Taroona”.

Summary - Bass Strait Triangulation observing

The following statistics are of interest:

Stations occupied



Intersected Points


19 (mainly for RAN charting)

Average triangular misclosure



Longest lines:

Deal Island


Mt Fatigue

83.8 miles


Deal Island


Mt Hunter

65.8 miles


Deal Island


Mt La Trobe

60.9 miles


Deal Island


Brougham Sugarloaf

51.9 miles


Chappell Isl.


Mt Cameron

48.9 miles


Mt Kerford


Cape Waterhouse

48.6 miles

Trig heights were carried through by simultaneous reciprocal vertical angles. With the computation of these a junction was made at Deal Island where there was a one foot difference between the value obtained from the Victorian Datum and the value obtained from the Tasmanian Datum. Figure 3 shows the triangulation scheme diagram. Progress to date is shown on the following Progress Map.

The observing teams had really learnt a lot on this survey. In particular the Wild T3 theodolite was a delight to use after the Wild T2. This gave the observers confidence which was lacking in their first task on Eyre Peninsula. Communications by the VHF radios were very good most of the time and they certainly made this survey possible. Unfortunately the new sets did not prove quite as reliable as the older sets used in the first phase. Relay trouble on occasions left an observer without a Receive, or alternatively without a Transmit capability. However with “one-way” communication available and some war-time knowledge of signalling by lights the observing parties were able to overcome this problem.

Field Party, November 1952 - April 1953

J. Hunter

Senior Surveyor

D.R. Hocking

Surveyor Grade 2 (acting)

E.J. Caspers

Field Assistant (Survey)

R.A. Ford

Field Assistant (Survey)

P.H. Lennie

Field Assistant (Survey)

R.G. Foster

Photogrammetric Draftsman

W.J. Dingeldei

Field Assistant

F.J. McCoy

Field Assistant

J. Jaggers

Field Assistant

J. Carrucan

Field Assistant

Figure 3: Triangulation scheme diagram.

Additional Photos

Ketch “Will Watch”

Observing with a Wild T3 theodolite

HMAS “Jabiru” (Jabiru was a survey tender for HMAS Warrego; GRL Rimington did most of his 1949 reconnaissance onboard Jabiru)(*)

MV “Taroona” (Bass Strait Ferry in those days)

ANA Bristol Freighter (*)

Loading Landrover (*)

Field Party members : Ted Caspers is 2nd from left and

Mr Robinson and his tractor used on Cape Barren Island to

Phil Lennie 5th (*)

transport survey equipment (*)

(*) These photos lifted from DR Hocking’s movies by Peter Hocking whose assistance is gratefully acknowleged

Deal Island (Note highest point from lighthouse)

Flinders Island