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This study estimates the uncertainty in Australian Height Datum (AHD) positional data, combining uncertainties from the 1971 adjustment and recent adjustments. It accounts for differences between published AHD values and those from recent adjustments, as well as uncertainties propagated during leveling. The standard deviation of height discrepancies between published and recent AHD values is analyzed. The results aim to resolve outliers and align with established knowledge that AHD accuracy in central Australia is approximately one foot (30 cm).
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Estimated AHD Positional Uncertainty • Derived from a recent homogeneous adjustment of the ANLN, constrained as in the 1971 AHD adjustment. • Combines: • Uncertainty in the 1971 adjustment: • Difference between the published AHD and the height from the recent adjustment & • Uncertainty due to the levelling propagation • Std Dev of the height from recent adjustment
Difference Between published AHD & recent adjustment Uncertainty of height in recent adjustment
Estimated AHD Positional Uncertainty • A few outliers to be resolved • Conforms with conventional wisdom of the originators of AHD: “accuracy of AHD in the centre of Australia is about a foot…” (1 foot ~ 30 cm)
