the geodetic datum for the eastern states, the Clarke 1858 reference ellipsoid and a British modified map grid based on the Transverse Mercator map projection with Australian zones. The first map with the British modified grid, for artillery purposes, was Albury '1 mile' although it was on the polyconic projection. This grid system was used for Australian topographic mapping until 1966. 1934–1939: undertook a 1st Order geodetic survey triangulation program to connect Queensland, New South Wales, Victoria and South Australia into one coherent network. Cooke, Troughton and Sims Tavistock 5 1/2-inch theodolites, reading direct to half-second for 1st Order work, replaced the larger and heavier 8-inch instruments and 3 1/2-inch Tavistocks reading direct to one second were used for second order work. Baselines of four to six miles in length were placed every 200 to 250 miles and measured with invar tapes standardised by steel bands. The use of field thermometers to estimate temperature corrections for thermal expansion of the measuring bands, was replaced with a system of measuring electrical resistance to estimate temperature coefficient of expansion to achieve accuracies of about 1 in 1 million (1 mm in 1 km) of the measured baselines. This world class research and development was in conjunction with Professor Kerr Grant, Department of Physics of University of Adelaide. Baselines for connecting the eastern Australia trigonometric network were measured at Jondaryn (QLD), Somerton (NSW), Benambra (VIC) and Tarlee (SA). 1936: the first map produced on the Transverse Mercator projection and the British modified grid – Helidon, Queensland 'one-mile' 1936: the first map compiled entirely from overlapping strip of air photography and graphical methods of rectification (Arundel method of radial line plotting) – Sale, Victoria 'one-mile'. Second World War: many innovative adaptions of equipment and processes for surveying, aerial photography for topographic compilation, cartography, photo-lithography, various printing methods and battlefield terrain modelling in base and field mobile situations to provide rapid response military survey/mapping support under adverse conditions of extreme heat, cold, high humidity, dust and rain in desert and jungle environments and at times under enemy attack 1952: topographic mapping by multi-projector (Multiplex anaglyph) stereoplotting from overlapping air photography, replacing graphical methods of rectification for map compilation 1953: large format Klimsch Commodore cartographic camera (remained in continuous use until December 1978) 1956: changed to decimal (also known as metric) scale mapping, largely as part of standardisation with allies in the South East Asia Treaty