Local Tie Technical Report 4 Summary

This local tie survey at Yaragadee (Moblas 5) was completed on the 1st to 3rd May 2001. The purpose of this survey was to repeat the determination of the invariant point of the Satellite Laser Ranging telescope (SLR IVP) and its relationship to the surrounding survey control, especially the SLR reference point DON95, the permanent GPS site YAR1 (DON95 RM4) and the permanent Glonass site YARR (AU053). The previous survey in August 1998 showed some differences from the original 1992 survey, especially in the area of DON95 RM4 (Johnston et al, 2000). This survey was intended to resolve the uncertainty created by those differences. The following report details the technique used in this survey and the results achieved. While internal consistency is of an extremely high standard some questions will be raised about the stability of the survey network in light of some of the differences encountered.

A Leica TC2003 total station was used for all horizontal angles, slope distances and zenith angles. Where zenith angles were to be used for vertical heightening, the Rueger method was used to determine the height of the trunnion axis of the total station. Simplistically, the Rueger method consists of observing a levelling staff over a known point with the vertical circle of the total station set to 90 degrees (horizontal) and reading the height value. This value, along with the known relationship between the two ground marks can then be used to determine a height of instrument. Where observations to the telescope for IVP determination were carried out, both face-left and face-right heights were observed to eradicated collimation effects. This was repeated at two targets per setup for extra redundancy.

• See the complete Technical Report 4 [PDF_250k]

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