GA Record Template€¦ · Web viewUpdated January 2013 2009 Mount Stromlo SLR Observatory Local Tie Survey Technical Report Geoscience AustraliaRECORD 2013/45 Ryan Ruddick1 and Alex

2009 Mount Stromlo SLR Observatory Local Tie SurveyTechnical Report

GEOSCIENCE AUSTRALIARECORD 2013/45

Ryan Ruddick1 and Alex Woods2

1. Geoscience Australia, GPO Box 378, Canberra, ACT, 2601, Australia2. Office of Surveyor-General Victoria, Land Victoria, Level 17/570 Bourke Street, Melbourne, Victoria, 3000, Australia

Department of Resources, Energy and TourismMinister for Industry: The Hon Ian Macfarlane MPParliamentary Secretary: The Hon Bob Baldwin MPSecretary: Ms Glenys Beauchamp PSM

Geoscience AustraliaChief Executive Officer: Dr Chris PigramThis paper is published with the permission of the CEO, Geoscience Australia

© Commonwealth of Australia (Geoscience Australia) 2013

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ISSN 2201-702X (PDF)

ISBN 978-1-922201-83-6 (PDF)

GeoCat 78503

Bibliographic reference: Ruddick, R. & Woods, A., 2013. 2009 Mount Stromlo SLR Observatory Local Tie Survey. Record 2013/45. Geoscience Australia: Canberra.

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http://www.creativecommons.org/licenses/by/3.0/au/deed.en

Contents

Executive Summary................................................................................................................................ 1

1 Introduction.......................................................................................................................................... 21.1 Methodology................................................................................................................................... 2

1.1.1 Field Observations.................................................................................................................... 21.1.2 Data Reduction......................................................................................................................... 21.1.3 Reporting.................................................................................................................................. 2

1.2 Site Description and Contacts........................................................................................................3

2 Instrumentation.................................................................................................................................... 42.1 Tachymeters, EDM and Theodolites..............................................................................................4

2.1.1 Description................................................................................................................................ 42.1.2 Specification............................................................................................................................. 42.1.3 Calibration................................................................................................................................ 4

2.2 Meteorological Sensor.................................................................................................................... 42.2.1 Description................................................................................................................................ 42.2.2 Specification............................................................................................................................. 4

2.3 Forced Centring............................................................................................................................. 52.3.1 Description................................................................................................................................ 52.3.2 Specification............................................................................................................................. 5

2.4 Targets and Reflectors................................................................................................................... 52.4.1 Description................................................................................................................................ 52.4.2 Calibration................................................................................................................................ 5

2.5 Precision Levelling......................................................................................................................... 52.5.1 Levelling Instruments................................................................................................................52.5.2 Levelling Rods.......................................................................................................................... 52.5.3 Levelling Staff........................................................................................................................... 6

2.6 Tripods........................................................................................................................................... 62.6.1 Description................................................................................................................................ 6

3 Measurement Network......................................................................................................................... 73.1 Terrestrial Network......................................................................................................................... 7

3.1.1 Primary Survey Control Points..................................................................................................73.2 Representation of Reference Points..............................................................................................8

3.2.1 SLR Reference Point................................................................................................................83.2.2 GNSS Reference Point.............................................................................................................83.2.3 DORIS Reference Point............................................................................................................8

4 Observations...................................................................................................................................... 104.1 Terrestrial Observations...............................................................................................................10

4.1.1 Horizontal Control Survey.......................................................................................................104.1.2 Vertical Control Survey...........................................................................................................10

4.2 Indirect Terrestrial Observations..................................................................................................104.2.1 SLR Telescope.......................................................................................................................10

2009 Mount Stromlo Local Survey

4.2.1.1 Azimuth Axis.....................................................................................................................114.2.1.2 Elevation Axis.................................................................................................................... 11

5 Data and Analysis.............................................................................................................................. 125.1 Process........................................................................................................................................ 125.2 Data Reduction............................................................................................................................ 12

5.2.1 Orthometric Levelling..............................................................................................................125.2.1.1 Procedure.......................................................................................................................... 125.2.1.2 Results.............................................................................................................................. 12

5.3 Data Processing........................................................................................................................... 135.3.1 Geodetic Adjustment..............................................................................................................13

5.3.1.1 Procedure.......................................................................................................................... 135.3.1.2 Results.............................................................................................................................. 13

5.4 IVP Determination........................................................................................................................ 135.4.1 Procedure............................................................................................................................... 135.4.2 Results.................................................................................................................................... 15

5.5 Global Alignment.......................................................................................................................... 155.6 Prism Offsets................................................................................................................................ 165.7 Comparison.................................................................................................................................. 16

5.7.1 IVP Coordinate Estimate........................................................................................................175.7.2 Local Survey Network.............................................................................................................175.7.3 Calibration Prisms...................................................................................................................18

References........................................................................................................................................... 20


Executive Summary

The integrity and strength of multi-technique terrestrial reference frames, such as realisations of the International Terrestrial Reference Frame (ITRF), depend on the precisely measured and expressed local-tie connections between space geodetic observing systems at co-located observatories. Australia has several observatories which together host the full variety of space geodetic observation techniques, including Global Navigation Satellite Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) beacons.

This report documents the technical aspects of the survey undertaken to determine the local-tie connections at the Mount Stromlo SLR Observatory. The Observatory is located next to the Australian National University (ANU) Research School of Astronomy and Astrophysics on Mount Stromlo in Canberra. The Observatory has a Satellite Laser Ranging (SLR) telescope co-located with three permanent GNSS sites, two of which contribute to the International GNSS Service (IGS) network. Nearby there is a national gravity observatory at the ANU school and a radio telescope used for Very Long Baseline Interferometry (VLBI) at the Canberra Deep Space Communication Complex (CDSCC) which is operated by NASA. The survey was conducted in November 2009 by surveyors from Geoscience Australia. Precision classical geodetic observations were combined with geodetic GNSS observations to determine the repeat relationship between the SLR system invariant point (IVP) and the conventional reference points of the GNSS antennas and the surrounding survey control.

The results of this survey have been provided to the International Earth Rotation Service (IERS) for inclusion in the next realisation of the ITRF.


1 Introduction

1.1 MethodologyThis report is not written to serve as a manual for precision geodetic surveys and it largely assumes that the reader has an understanding of the basic concepts of geodetic surveying. Furthermore, this report does not detail or justify the approach taken, but merely reports the results of each major computation step. For an in-depth analysis and justification of the approach taken the reader is referred to Dawson et al, 2007. However for completeness the steps in our approach for observation and computation of local-ties relationships are as follows:

1.1.1 Field Observations

The calibration of all geodetic instrumentation,

The observation of a vertical geodetic network,

The observation of a horizontal geodetic network,

The observation of a GNSS network on at least three suitable survey marks,

The observation of targets located on the observing system during rotational motion about each of its independent axis, including the observation of zenith angles to a staff on levelled survey marks for the precise determination of instrument height.

1.1.2 Data Reduction

The reduction of the terrestrial geodetic observations, including correction for instrument and target bias, angular set reduction and atmospheric effects,

The estimation of coordinates and their associated variance-covariance matrix in a local system, through a classical geodetic least squares adjustment (minimum constraint),

The estimation of the system IVP, the axes of rotation and associated system parameters, such as axis orthogonality and offset,

The analysis of the GNSS observations,

The transformation (translation and rotation) of the terrestrial network, computed system IVP and variance-covariance matrix onto a global reference frame defined by the GNSS analysis.

1.1.3 Reporting

The coordinate estimates and their associated variance-covariance information is provided to the IERS and made available on-line (ftp.ga.gov.au) in the form of a SINEX file.


ftp://ftp.ga.gov.au/geodesy-outgoing/local_tie/

1.2 Site Description and ContactsThe Mount Stromlo Laser Ranging Observatory is located next to the Australian National University (ANU) Research School of Astronomy and Astrophysics on Mount Stromlo in Canberra. The Observatory has a Satellite Laser Ranging (SLR) telescope co-located with three permanent GNSS sites. Nearby there is a national gravity observatory at the ANU school and a radio telescope used for Very Long Baseline Interferometry (VLBI) at the Canberra Deep Space Communication Complex (CDSCC) which is operated by NASA. Similar local surveys were undertaken in 2003, after the bush fire destroyed a large part of the observatory, and in 2006.

Before undertaking the survey the following people should be consulted in regards to site access, survey timing and interference with observing systems:

Site Contact: Chris Moore – EOS Space SystemsEmail [email protected] +61 2 6222 7979

Gravity Contact: Nicholas Dando – Geoscience AustraliaEmail [email protected] +61 2 6249 9552

GNSS Contact: Ryan Ruddick – Geoscience AustraliaEmail [email protected] +61 2 6249 9426





2 Instrumentation

This section provides the specifications and calibration procedures of the equipment used in the survey.

2.1 Tachymeters, EDM and Theodolites

2.1.1 Description

A Leica TCA2003 (S/N 439124) total station was used to record all angles and distance measurements.

2.1.2 Specification

Electronic Distance Measurement (EDM) (infrared) distance standard deviation of a single measurement (DIN 18723, part 6): 1.0 mm ± 1 ppm.

Angular standard deviation of a mean direction measured in both faces (DIN 18723, part 3): 0.15 mgon (≈ 0.49°).

2.1.3 Calibration

The Leica TCA2003 (S/N 439124) was serviced by C.R. Kennedy (Sydney, Australia) in April 2009, during which the instrument was checked to ensure compliance with manufacture specifications.

2.2 Meteorological Sensor

2.2.1 Description

A NK Kestrel 4000 Pocket Weather Tracker (S/N 516991) was used to record meteorological observations (temperature, pressure and relative humidity).

2.2.2 Specification

Temperature is accurate to 1.0°C between -29.0°C and 70.0°C.

Pressure is accurate to 1.5 mb at 25°C between 750 mb and 1100 mb.

Relative humidity is accurate to 3.0%.


2.3 Forced Centring

2.3.1 Description

An FG0L30 (S/N 609030) zenith and nadir optical plummet was used to centre and level all instrument and target setups.

2.3.2 Specification

Accuracy is 1:30 000 (1 mm at 30 m).

2.4 Targets and Reflectors

2.4.1 Description

The standard target kit includes:

4 x Leica GDF21 tribrachs.

4 x Leica GZR3 prism carriers with optical plummet.

4 x Leica GPH1P precision prisms.

6 x Leica GMP101 mini prisms.

2.4.2 Calibration

The additive constant for the Leica GPH1P precision prism is -34.4 mm which was applied directly into the Leica TCA2003 total station. All prisms were calibrated on a tripod baseline at Geoscience Australia in July 2009. Prism corrections were applied to observations during data processing.

Leica GMP101 mini prisms were calibrated at Geoscience Australia in July 2009. Approximate prism corrections of +18.5 mm were applied to observations during data processing.

2.5 Precision Levelling

2.5.1 Levelling Instruments

Refer to section 2.1 for a description of the Leica TCA2003 total station.

2.5.2 Levelling Rods

A fixed height stainless steel rod (ARGN3) approximately 1.5 m in height with Leica style bayonet mount on top for mounting a precision prism was used with a Leica bi-pod for stability.

A fixed height stainless steel stub (Stub3) approximately 0.2 m in height with Leica style bayonet mount on top for mounting a precision prism.


A height offset between the pole (ARGN3) and the stub (Stub3) was determined by observing both on a low mark. Multi-set, dual face observations were used to eliminate collimation effects. The resulting height offset was 1.4061 m.

2.5.3 Levelling Staff

A Topcon fibreglass levelling staff was used in the determination of precise instrument heights.

2.6 Tripods

2.6.1 Description

Leica GST20/9 heavy duty timber tripods with adjustable legs were used on all marks with the exception of the pillars.


3 Measurement Network

3.1 Terrestrial Network

3.1.1 Primary Survey Control Points

Table 3.1 The primary survey control points observed during the survey.

Name 4-Char ID DOMES Description

AU45 STR2 50119M001 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. The pillar plate is inscribed with “AU045 Fundamental Pillar”.

AU46 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. This is the north calibration pillar.

AU47 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. This is the north-east calibration pillar and was re-aligned in September 2009.

AU48 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. This is the south-east calibration pillar.

AU49 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. This is the south calibration pillar.

AU52 STR1 50119M002 The intersection of the top of the stainless steel prism holder with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. The prims holder is attached directly to AU46. The offset between AU46 and AU52 is 0.182 m.

AU54 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot.

AU60 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. This pillar is located on the western edge of the roof of the SLR building.

AU61 The intersection of the top of the stainless steel plate with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. This pillar is located on the eastern edge of the roof of the SLR building.

STR3 STR3 The intersection of the top of the stainless steel prism holder with the vertical axis of the 5/8 inch Whitworth threaded stainless steel spigot. This is the north-west calibration pillar.

DORIS MSPB 50119S004 The intersection of the DORIS antenna with the plane coinciding with the base of the reference height line marked on the DORIS antenna.

SLR IVP 7825 50119S003 The intersection of the estimated azimuth axis and elevation axis of rotation of the SLR telescope.

TRIG The original Mount Stromlo geodetic survey mark. A .303 cartridge set in concrete beneath a steel quadrapod.

1586 Levelling benchmark located to the north-east of the observatory. It consists of a stainless steel rod with a centre punch mark at the top.


Name 4-Char ID DOMES Description

AU45 RM1 and RM2

Stainless steel reference pins with a centre punch mark on top.

….R An “R” as the suffix denotes the SLR calibration targets on the calibration pillars.

3.2 Representation of Reference Points

3.2.1 SLR Reference Point

There is one SLR telescope used for geodetic observations at the Mount Stromlo Observatory. The telescope is an azimuth-elevation style and was established in 2003. The reference point of the telescope, referred to as the system invariant point (IVP), is a theoretical point defined by the intersection of the azimuth axis with the common perpendicular of the azimuth and elevation axes. An indirect survey was used to determine this point.

3.2.2 GNSS Reference Point

There are three permanent GNSS antennas at the Observatory. The antennas are mounted on pillars attached to bedrock with the antennas aligned to true north. The conventional reference point for the antennas is described as the intersection of the top of the stainless steel pillar plate with the vertical axis of the 5/8 inch Whitworth threaded spigot. For STR1 this point corresponds with the antenna reference point (ARP). All of the antennas were removed during this survey.

3.2.3 DORIS Reference Point

There is one DORIS beacon at the Observatory. The conventional reference point of the beacon is described as the intersection of the beacon with the plane coinciding with the base of the reference height line marked on the beacon.


Figure 3.1 Mount Stromlo SLR Observatory terrestrial survey network.


4 Observations

4.1 Terrestrial Observations

4.1.1 Horizontal Control Survey

A terrestrial network survey was conducted between the permanent survey marks within the Mount Stromlo Observatory. Five sets of observations were completed at each standpoint; a set consists of a round of face left observations, followed by a round of face right observations to each of the visible survey marks. For each observation a horizontal direction, zenith angle and slope distance was recorded. At each instrument set-up atmospheric conditions (temperature, pressure and relative humidity) were recorded. Atmospheric conditions were applied during post-processing and not directly into the total station. Instrument and target heights were measured using an offset tape.

During the survey the GNSS antennas were removed and direct observations made to and from the survey pillars.

4.1.2 Vertical Control Survey

Precise levelling was conducted between the survey pillars and reference marks using the EDM height traversing technique (Reuger and Brunner 1981). Height difference observations were made using a Leica TCA2003 total station to a prism mounted on a fixed height stainless steel pole and to a fixed height stainless steel stub. Atmospheric conditions (temperature, pressure and relative humidity) were recorded every 30 minutes and entered directly into the total station.

Levelling loops to all monuments in the survey network were completed in both directions. Each instrument set-up involved reading three rounds of face left and face right observations to a single prism set-up over two marks.

4.2 Indirect Terrestrial Observations

4.2.1 SLR Telescope

The SLR telescope was observed from two instrument standpoints (AU45 and STR3). From each standpoint one set of observations was made to each of the visible targets. Each set of observations consists of a round of face left observations, followed by a round of face right observations. For each observation a horizontal direction, zenith angle and slope distance was recorded. Every 60 minutes atmospheric conditions (temperature, pressure and relative humidity) were recorded. Atmospheric conditions were applied during the post-processing and not directly into the total station. After each set of observations the telescope was rotated in set increments for first azimuth and then elevation, until the telescope was rotated through 360° for azimuth and 180° for elevation.


At each standpoint the height of instrument was determined before and after each observation session using the technique described by Reuger and Brunner (1981). The measurement technique involved the observation of a single round of face left and face right vertical angles to specific graduations on a levelling staff (in this case 2.0, 1.6, 1.2 and 0.8 m) placed on two nearby, levelled survey marks.

4.2.1.1 Azimuth Axis

For the azimuth axis:

Observations were made from the standpoints AU45 and STR3.

Three mini prisms were mounted to the substructure of the telescope using magnetic mounts.

The elevation axis was fixed.

The azimuth axis was rotated in 20° increments through 360°.

4.2.1.2 Elevation Axis

For the elevation axis:

Observations were made from the standpoints AU45 and STR3.

Four mini prisms were mounted to the substructure of the telescope using magnetic mounts.

The azimuth axis was fixed at 91° and 355° for the standpoints respectively.

The elevation axis was rotated from 0° to 180° in 10° increments.


5 Data and Analysis

5.1 ProcessThe data analysis can be split into five steps:

Data Reduction – angular sets reduced, prism offsets and atmospherics applied,

GNSS Analysis – coordinates estimated in a global reference frame,

Classic Geodetic Adjustment – coordinates estimated in a local reference frame,

IVP Determination – system reference points and tie vectors estimated,

Transformation – alignment of the survey to a global reference frame.

5.2 Data Reduction

5.2.1 Orthometric Levelling

5.2.1.1 Procedure

The levelling observations were reduced using Geoscience Australia’s levelling reduction application. Height differences were determined between all survey marks. The misclosure was noted as being well within zero order specifications. The results were added into the survey adjustment with a precision of 0.0002 m.

5.2.1.2 Results

Table 5.1 Orthometric heights (in metres) derived with respect to AU45 (STR2) from the 2009 survey compared with the 2003 (post-fire) and 2006 surveys.

AU45 to … 2003 2006 2009 σ (m)

AU46 -2.7314 -2.7315 -2.7311 0.0003

AU47 4.6889 4.6876 4.6882 0.0003

AU48 -0.9367 -0.9363 -0.9351 0.0003

AU49 -7.9697 -7.9693 -7.9688 0.0003

AU54 -3.7628 -3.7628 -3.7638 0.0003

AU60 - 0.8962 0.8961 0.0003

AU61 - 1.8059 1.8055 0.0003

STR3 - -3.4452 -3.4452 0.0003

1586 - -5.4965 -5.4975 NA

TRIG 1.0846 1.0839 1.0838 NA


5.3 Data Processing

5.3.1 Geodetic Adjustment

5.3.1.1 Procedure

The geodetic adjustment was undertaken using Dynanet (v 3.08) (Fraser et al, 2013). In the adjustment AU45 (STR2) was minimally constrained to its ITRF2000 coordinates and AU46 was minimally constrained in a longitudinal direction. The angular observations were given a precision of 1.0” and the slope distances given a base precision of 1.0 mm. The estimated coordinates and associated variance-covariance matrix in a local topocentric system was output as a SINEX file.

5.3.1.2 Results

Table 5.2 Local topocentric vectors (in metres) between AU45 and the surrounding survey control from 2009.

AU45 to … de dn du

AU46 -9.2911 69.6446 -2.7315

AU47 25.6967 21.8581 4.6880

AU48 49.3484 -88.6286 -0.9359

AU49 -67.4328 -30.0221 -7.9691

AU52 -9.2911 69.6446 -2.5491

AU54 -43.4766 8.6562 -3.7638

AU60 -28.5237 9.3048 0.8960

AU61 -15.7924 6.4620 1.8054

MSPB -15.8578 6.1397 2.4314

STR3 -25.5947 51.7637 -3.4454

5.4 IVP Determination

5.4.1 Procedure

The geometrical modelling and adjustment processes were undertaken in Axis (v 1.08) (Dawson et al, 2007). The SINEX file containing the estimated coordinates and variance-covariance matrix in a local topocentric reference frame was used as input for Axis.

The method of IVP determination involves the derivation of independent axes of rotation of the telescope through a process of 3-dimensional circle fitting to the 3-dimensional coordinates of targets observed at points on the telescope during rotational sequences. A least squares method was used for the computation of the axes of rotations and the system IVP. The method works on the basis that a target located on a rigid body, rotating about one independent axis can be fully expressed as a circle in 3-dimensional space and described by seven parameters:

A circle centre (3 parameters),


A unit normal vector, perpendicular to the circle (3 parameters),

A circle radius (1 parameter).

The method of IVP determination makes assumptions that:

During a rotational sequence target paths scribe a perfect circular arc in 3-dimensional space,

There is no deformation of the targeted structure during rotational sequence,

There is no wobble error,

The axis of interest can be rotated independently of the other axis.

No assumptions of axis orthogonality, verticality / horizontality or the precise intersection of axes are made.

The indirect geometrical model includes a number of conditions, including:

Target paths during rotations about an independent axis scribe a perfect circle in space,

Circle centres derived from targets observed while being rotated about the same axis are forced to lie along the same line in space,

Normal vectors to each circle derived from targets observed while being rotated about the same axis are forced to be parallel,

The orthogonality of the primary axis to the secondary axis remains constant over all realisations of the secondary axis,

Identical targets rotated about a specific realisation of an axis will scribe 3-dimensional circles of equal radius,

The offset distance between the primary and the secondary axis remains constant over all realisations of the secondary axis,

The distance between 3-dimensional circle centres for all realisations of the secondary axis are constant over all realisations of the secondary axis,

The IVP coordinate estimates remain constant over all realisations (combinations) of the primary/secondary axis.

In addition, a constraint that the unit normal vector perpendicular to the plane of the circle must have a magnitude of one applied and a minimum of three rotational sequences for each target was required to enable the solution of the equation of a circle.

The linearized equations take the form of twos sets of equations, namely conditions and constraints with added parameters:

Av+BΔ=f (1)

D1Δ+D2Δ'=h (2)

Where vis the parameter vector of residuals of the input classical adjustment results, ∆ is the parameter vector of the circle parameters, ∆ ' is the parameter vector of the parameters associated with IVP estimates, f and h are the constant vectors associated with the evaluation of the conditions


and constraints respectively and A ,B , D1 and D2 are matrices of coefficients. The least squares solution is obtained from the following system of normal equations:

[−W At 0 0 0A 0 B 0 00 B t 0 D1

t 00 0 D1 0 D20 0 0 D2

t 0][ vkΔk cΔ ' ]=[0f0h

0]

(3)

Where W is the weight matrix of the input coordinates derived from the classical adjustment and k and k c are vectors of the Lagrange multipliers required to satisfy the least squares criteria.

The solution to the normal equation is iterated as required for non-linear condition and constraint equations. An updated estimate of the input coordinates and their variance-covariance matrix is obtained together with an estimate of the IVP coordinate their variance-covariance matrix and the inter-relating covariance matrix.

The solution for the IVP included 747 observations to 14 targets. There were two estimates of the IVP for the point 7825 50119S003 which were constrained together through 30 separate constraints. The resultant linear system for the network was 747 x 747 with 1203 degrees of freedom. The computed variance factor was 0.185. The maximum circle fit residual was 1.2 mm.

5.4.2 Results

Along with the coordinate estimates and associated variance-covariance matrix in a local reference frame, the following system parameters specific to the telescope were determined:

The azimuth axis deflection of the vertical is 0°00’30.55”.

The orthogonality of the azimuth to elevation axis is 89°59’42.88”.

The offset distance between the azimuth and elevation axis is 0.0002 m.

Table 5.3 Local topocentric vectors (in metres) between AU45 and the surrounding survey control from 2009.

7825 to … de dn du

AU45 (STR2) 24.9531 -2.0066 -2.4997

AU52 (STR1) 15.6626 67.6383 -5.0488

STR3 -0.6413 49.7576 -5.9451

MSPB (DORIS) 9.0953 4.1333 -0.0683

5.5 Global Alignment

The estimated coordinates in a local topocentric reference frame were not aligned to a global reference frame. Instead the ITRF2000 coordinate of AU45 and the azimuth to AU46, as obtained from the 2003 survey, were used to align the survey.


Table 5.4 Final Cartesian coordinates (in metres) with 1σ precision estimates, aligned to the ITRF2000 coordinate of AU45 (STR2) orientated to the ITRF coordinate of AU46.

Station ID X Y Z

AU45 50119M001 -4467074.6878 ± 0.0005 2683011.8687 ± 0.0005 -3667007.8238 ± 0.0005

AU61 50119M004 -4467071.0218 ± 0.0005 2683028.0889 ± 0.0005 -3667003.5946 ± 0.0005

MSPB 50119S004 -4467071.2663 ± 0.0005 2683028.3120 ± 0.0006 -3667004.2194 ± 0.0005

7825 50119S003 -4467064.5827 ± 0.0005 2683034.9074 ± 0.0005 -3667007.6315 ± 0.0005

STR3 50119M005 -4467084.7522 ± 0.0005 2683047.7698 ± 0.0005 -3666963.5938 ± 0.0005

STR1 50119M002 -4467102.6350 ± 0.0005 2683039.4920 ± 0.0005 -3666949.5217 ± 0.0005

AU46 -4467102.5074 ± 0.0005 2683039.4154 ± 0.0005 -3666949.4163 ± 0.0005

AU47 -4467102.0302 ± 0.0005 2682998.3155 ± 0.0005 -3666992.6983 ± 0.0005

AU48 -4467055.5198 ± 0.0006 2682942.7914 ± 0.0006 -3667079.6017 ± 0.0005

AU49 -4467019.5152 ± 0.0006 2683057.3923 ± 0.0006 -3667027.7137 ± 0.0006

5.6 Prism OffsetsThe SLR system at Mount Stromlo Observatory regularly ranges to terrestrial targets located on five of the surrounding pillars. The terrestrial laser observations are used to calibrate the system, including calculation of the system delay.

The prism offsets were calculated using a two pillar baseline between AU45 and STR3. Repeat face left and face right observations were made between the pillars to each of the calibration prisms. The prisms offsets were calculated and added to the IVP to calibration pillar baselines.

Table 5.5 Local topocentric vectors between the SLR IVP and the calibration prisms.

7825 to … de dn du Range (m)

AU46 R (N) 15.6572 67.6136 -5.1303 69.5921

AU47 R (NE) 50.6310 19.8438 2.2847 54.4290

AU48 R (SE) 74.2838 -90.6151 -3.3396 117.2190

AU49 R (SW) -42.4598 -32.0126 -10.3652 54.1763

STR3 R (NW) -0.6410 49.7323 -5.8451 50.0787

5.7 Comparison

Local surveys have previously been carried out in 2003 (post-fire) (Johnston et al 2004) and 2006 (Woods 2007). This section shows the comparisons between the previous survey results with the 2009 survey.


5.7.1 IVP Coordinate Estimate

Table 5.6 shows the estimates of the system IVP coordinates from the three surveys. There is good agreement the 2006 and 2009 surveys. The differences are well within the expected error bounds of the survey.

Table 5.6 Comparison of the Cartesian coordinates of the system IVP (in metres) with the 1σ precision estimates aligned to the ITRF2000 coordinates of AU45 (STR2), AU52 (STR1) and AU61.

Station ID X Y Z

2009 -4467064.5827 ± 0.0005 2683034.9074 ± 0.0005 -3667007.6315 ± 0.0005

2006 -4467064.5844 ± 0.0001 2683034.9069 ± 0.0001 -3667007.6316 ± 0.0001

2003 -4467064.5807 ± 0.0001 2683034.9070 ± 0.0001 -3667007.6305 ± 0.0001

5.7.2 Local Survey Network

Tables 5.7 to 5.9 show the residuals in the local vectors from the system IVP between the individual surveys and the mean of the three surveys. The results indicate good agreement in the horizontal (east and north) components. Again the agreement between the 2006 and 2009 surveys is relatively good. One point of concern is the possible instability of AU61 which has been used in all surveys as an alignment point to the global reference frame. In future surveys, the alignment of the survey should be made using the three permanent GNSS sites.

Table 5.7 Residuals (mm) in the local vectors from the system IVP between the 2003 survey and the mean of the three surveys.


AU45 -0.9 0.2 -1.1

AU61 -2.4 -0.9 -1.3

STR3 - - -

STR1 -1.2 0.6 -1.3

AU46 -1.1 0.5 -1.0

AU47 0.4 -0.5 -2.2

AU48 -1.8 1.7 -0.8

AU49 -1.4 0.6 0.7



AU45 -0.6 -0.1 -0.8

AU61 1.0 -0.2 0.5

STR3 0.0 0.5 -0.2



STR1 1.0 0.4 0.8

AU46 1.0 0.5 0.7

AU47 2.6 -2.0 1.7

AU48 0.2 -0.8 1.9

AU49 0.0 -0.1 -0.2



AU45 0.0 -0.3 0.2

AU61 1.5 1.1 0.8

STR3 0.0 -0.5 0.2

STR1 0.1 -0.9 0.5

AU46 0.2 -0.9 0.4

AU47# -3.0 2.5 0.4

AU48 1.5 -0.9 -1.0

AU49 1.4 -0.4 -0.6

# The pillar AU47 was re-aligned between the 2006 and 2009 surveys.

5.7.3 Calibration Prisms

Tables 5.10 to 5.12 show the local vectors between the system IVP and the calibration prisms. Good agreement is shown between the 2003 and 2006 surveys. The 2009 survey indicates a significant difference in the vertical (up) component. This is most likely attributed to the methodology used. In the 2003 and 2006 surveys the calibration prisms were taken to the Watson baseline for calibration. In 2009 the prisms were calibrated on site using a two pillar baseline. Until a new survey is undertake the suggestion would be to use the local vectors from the 2006 survey for any SLR system calibrations.

Table 5.10 Local vectors between the system IVP and the calibration prisms from the 2003 survey.


AU46 R (N) 15.6583 67.6127 -5.1257 69.5912

AU47 R (NE) 50.6243 19.8456 2.2953 54.4237

AU48 R (SE) 74.2868 -90.6180 -3.3310 117.2230

AU49 R (SW) -42.4574 -32.0131 -10.3644 54.1747

STR3 R (NW) - - - -




AU46 R (N) 15.6561 67.6130 -5.1267 69.5911

AU47 R (NE) - - - -

AU48 R (SE) 74.2853 -90.6154 -3.3357 117.2202

AU49 R (SW) -42.4593 -32.0134 -10.3636 54.1761

STR3 R (NW) -0.6409 49.7322 -5.8410 50.0781



AU46 R (N) 15.6572 67.6136 -5.1303 69.5921

AU47 R (NE) 50.6310 19.8438 2.2847 54.4290

AU48 R (SE) 74.2838 -90.6151 -3.3396 117.2190

AU49 R (SW) -42.4598 -32.0126 -10.3652 54.1763

STR3 R (NW) -0.6410 49.7323 -5.8451 50.0787


References

Dawson, J., Sarti, P., Johnston, G., Vittuari, L., 2007. Indirect approach to invariant point determination for SLR and VLBI systems: an assessment. Journal of Geodesy. June 2007, Vol. 81, Issue 6-8. pp 433-441.

Fraser, R., Leahy, F., Collier, P., 2013. Dynanet User’s Guide Version 3.0. Dynamic Network Adjustment Software.

Johnston, G., Dawson, J., Naebkhil, S., 2004. The 2003 Mount Stromlo Local Tie Survey. Record 2004/020. Geoscience Australia: Canberra.

Rueger, J. M., Brunner, F. K., 1981. Practical Results from EDM-Height Traversing. The Australian Surveyor. June 1981, Vol. 30, No 6.

Woods, A., 2007. The 2006 Mount Stromlo Local Tie Survey. Record 2007/018. Geoscience Australia: Canberra


GA Record Template€¦ · Web viewUpdated January 2013 2009 Mount Stromlo SLR Observatory Local Tie Survey Technical Report Geoscience AustraliaRECORD 2013/45 Ryan Ruddick1 and Alex

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