For a surveyor to find actual true north, it is quite an involved process. Ideally, they have to find 2 permanent marks in the near vicinity with a known bearing between them based on the GDA94, and assuming this is the case, the surveyor would then place a temporary benchmark (TBM) on the desired location on your property.
Then they would set their total station up on top of the permanent mark with known coordinates, and sight to the other mark (by using a prism mounted on a tripod on the other mark) and then input the GDA94 bearing into the machine. Then the procedure is to traverse from the original station to where the scope will be placed. Common procedure for this is once a bearing is established, a second prism will be placed on a temporary benchmark located towards the intended target, that is a point selected by the surveyor. With a known GDA94 bearing now input into the total station, they will have to traverse to the desired location. Prisms will be placed either side of the total station - toward the intended target and back "behind" it on the previous mark, this can be either known permanent marks or temporary marks that the surveyor creates. Using the original bearing, the surveyor will swing the total station to both next and preceeding mark, both clockwise and counterclockwise (foresight and backsight), for a total of 4 readings between each mark, known as "face left" and "face right". This is done for accuracy and redundancy. The total station, using the original bearings between the two known points, will show accurate bearings to each successive mark. Eventually, the total station will end up on the final temporary mark (which will mark the location of the telescope) , and by simply sweeping horizontally with the station using the bearings already found, the station will display the true bearing as it is swung around. True north can now be found to an accuracy of less than 5 arc seconds.
An alternate method is using northing and easting coordinates. Bearing and distance can be found using the eastings and northings of two points. This is handy if there are no known bearings between two marks, It is possible to work out the required parameters using mathematical formulas. Then the surveyor can proceed to find any other point they desire as per the process I described above.
