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1 Australian Fundamental Gravity Network, 1992 Coober Pedy - Mt Willoughby Gravity Tie, South Australia Operations Report by John W. Williams AGSO Record 1997/32-1~/) ~<>. 6-mR. (()W\ P 0 lq/rtl.~2- ~ Co~3 <. v ~ ' ( '. AUSTRALIAN GOLOGICAL SURVY O R GAN I SAT I ON

2 AUSTRALIAN FUNDAMNTAL GRAVITY NTWORK 1992 COOBR PDY - Mt WILLOUGHBY GRAVITY TI, SOUTH AUSTRALIA OPRATIONS RPORT by John W Williams AUSTRALIAN GOLOGICAL SURVY ORGANISATION Record 1997/32 June 1997

3 DPARTMNT OF PRIMARY INDUSTRIS AND NRGY Minister for Primary Industries and nergy: Hon. J. Anderson, M.P. Minister for Resources and nergy: Senator the Hon. W.R. Parer Secretary: Paul Barratt AUSTRALIAN GOLOGICAL SURVY ORGANISATION xecutive Director: Neil Williams Commonwealth of Australia 1997 ISSN: ISBN: This work is copyright. Apart from any fair dealings for the purposes of study, research, criticism or review, as permitted under the Copyright Act 1968, no part may be reproduced by any process without written permission. Copyright is the responsibility of the xecutive Director, Australian Geological Survey Organisation. Requests and inquiries concerning reproduction and rights should be directed to the Manager, Corporate Publications, Australian Geological Survey Organisation, GPO Box 378, Canberra City, ACT, 2601 AGSO has endeavoured to use techniques and equipment to achieve results and information as accurately as possible. However such equipment and techniques are not necessarily perfect. AGSO has not and does not make any warranty, statement or representation about the accuracy or completeness of any information contained in this document. USRS SHOULD NOT RLY SOLLY ON THIS INFORMATION WHN CONSIDRING ISSUS WHICH MAY HAV COMMRCIAL IMPLICATIONS.

4 CONTNTS Summary 1 Introduction 2 Survey Method and Operations 3 Survey Data Processing 4 Survey Results 4 FIGURS 1. Locality Plan of Fundamental Gravity Network - Central South Australia. APPNDICS 1. Field Party and quipment. 2. Gravity Base Station Location Diagrams and Control information. 3. Field Observations. 4. Tidal Gravity Corrections. 5. Processing Summary and Statistics.

5 LOCATION OF SURVY \j ' ' ' s-; ,---::::-== ;;;----=;::--::-: "(""-:-~.. :_::: --_, ' S.; ( '~~~~~~---~~~~--~------~~~~~~--~~~ ' S ' '

6 SUMMARY This report describes gravity meter ties conducted to establish new gravity control stations at the Coober Pedy aerodrome in South Australia. Two LaCoste and Romberg gravity meters ( G 132. and G252) were used to measure the gravity intervals during the survey. The control station used for this survey was at Mt Willoughby airstrip windsock. station The new control stations have been marked with inscribed brass identifier discs glued onto concrete at the observation sites. The following table summarises the new station values. Station locations have not been surveyed and are only approximate. NW STATIONS STABLISHD DURING THIS SURVY Station ID Latitude Longitude Location Gravity ~.2 Ties ' ' Coober Pedy Terminal : ' ' Coober Pedy NS Windsock :2 Australian Geological Survey Organisation

7 2 INTRODUCTION The Australian Geological Survey Organisation (AGSO) has the responsibility of maintaining the Australian Fundamental Gravity Network (AFGN), previously known as the Isogal Network. This network provides a consistent gravity datum to control all gravity surveys carried out in and around Australia. AGSO is currently putting additional effort into a project to refurbish the AFGN since the last systematic survey of the network in A large number of base stations have been destroyed by redevelopment of roads and buildings etc. During each annual survey program while progressively restoring and augmenting the AFGN, new control stations are installed in areas needed by Government departments and the mineral exploration industry where there is only a sparse distribution of control stations. The aim of this survey was to establish new control stations at the Coober Pedy Airstrip following a request by BHP xploration to improve the coverage of gravity control stations in the Coober Pedy area. On the 22 of May 1992, the Gravimetry Section of AGSO performed a gravity survey in the Coober Pedy - Mt Willoughby area of South Australia establishing new gravity control stations ( and ) at the Coober Pedy Airstrip. The new stations were tied to an existing gravity station at the Mt Willoughby airstrip windsock, station numbered Two La Coste and Romberg gravity meters (G 132 & G252) were read by one operator over one day. Australian Geological Survey Organisation

8 3 SURVY MTHOD AND OPRATIONS The field party consisted of Harry Reith (Technical Officer grade 2), with a Toyota L WB 4WD vehicle, and two La Coste and Romberg gravity meters, G 132 and G252. While travelling between survey locations, the opportunity was taken while in the Coober Pedy area to tie gravity control station at Mt Willoughby to two new stations and at the Coober Pedy airstrip. Two loops (3:2tie), using two meters, were made over a period of 10 hours on the 22May Data was recorded using a Husky Hunter data logger for processing at Canberra. AustraIian Geological Survey Organisation

9 4 SURVY DATA PROCSSING The Husky Hunter data logger was down loaded in the field and the data sent to Canberra on a floppy disc for processing on a Sun computer (via an IBM PC) by J W Williams. The field data from the two meters was re-formatted to an input me format suitable for calculation of arth tidal gravity correction, drift and gravity interval using AGSO programs RTID and GRVHTS. The readings were arranged to form loops which were then corrected for earth tide, results of which are shown in Appendix 4. The corrected readings were then input to the network adjusting program which used the two unknown stations as nodes, the primary control station being at Mt Willoughby. The closed loops defined the drift of each meter. The drift and tide corrected measured gravity intervals between the nodes for each loop and for each meter, were least square adjusted to provide best fit values for all measured intervals. Final gravity values were then calculated for each station using the control station value and the adjusted intervals. RSULTS Both meters performed well. Adjustments for and between meters were better than 0.26 ~ms 2.The standard deviation of adjusnnents was 0.16 pms- 2 All readings have been used for the final processing as shown in Appendix 5. The final gravity values are shown in the following table. FINAL GRAVITY VALUS STATION LATITUD LONGITUD HIGHT GRAVITY LOCATION NUMBR degrees degrees m Jlms- l MT WILLOUGHBY WINDSOCK COOBR PDY TRMINAL COOBR PDY WINDSOCK Australian Geological Survey Organisation

10 Personnel; Gravity Meters Vehicle Other quipment 5 APPNDIX I Field Party and quipment Harry Reith (Technical Officer grade 2), LaCoste and Romberg numbers G 132 and G252. ToyotaLWB 4WD. Husky Hunter Data Logger, Base plates camera, cement, station markers. Australian Geological Survey Organisation

11 6 APPNDIX 2 Gravity Base Station Location Diagrams. The following diagrams describe the locations of the Fundamental Gravity Network stations measured on this survey. The descriptions and gravity values shown are accurate at the time of installation (May 1992) but these may change to some degree as the envroment around each station is modified in the future. Control Information. The reference value used to control the gravity datum for this survey was jlms 2 at the MtWilloughby airstrip windsock; gravity station number as shown on Station diagram Mt Willoughby Sheet 1 of 1. Australian Geological Survey Organisation

12 ST,AJJ~ N.Afv COOBR PDY ST,AJJ~~ 1.OC.All~ DSCRIBD I RCO\ RD BY CSSIMD GRA\fIY (J.l.ms.2) Coober Pad{ M WnctOCk " H ReHh i!zl.-'iy.77jl) Zl!lotd;_ I DSCRIPTlOO: $bal1ov T'rP: PCSTlaJ: PosItfon SoU'ce: LV.Al1aJ: Bt!M:1ffon SoU'ce: Base S 29 02' 30" ' 00" CM nroute Supplement 254. m CM * Bross disc placed on round concrete block marked ' LC ' 9293.~ ~p OPo lo.4m 0 l 0 It\oII:lQrock 0 0 IMndsock Cones 0 0 On 0 2 \.ert1col ~es 1.Sm high 0 N To Coober Pedy :...:,.'-= t--r GRA'v1lY STATlOf\JS,AL5TR,AU,AN NA1l0N,Al GRA\i1lY NT\AORK StaHon Oass: BuilD I Terminal D.AJ tvby 1992 Wndsock AGSO.as AUSTRALIAN GBC\.OGICAL S!JlVI!Y Oi ea-hai ATloN

13 stajlon NA'v COOBR PDY stajlon~ ~ON DSCRIBD I RCO\ RD BY I H ReIth I Coober R9dy IVS Terminal!Zl.- &",7TJ/) 1II.It4J DSCRIPTlOO: 5rA11(X\J T'tP: l3ce PCST100: S 2902' 30" 13443' 00" PosJfIon Sotrce: LV,41100: 254. m J9\allon Sotrce: N * Wndow 1 Fuel - I nclosurb '----, L I, Te~lnal 0 1 Buldlng I ,Apron \t\bter Tank \ 1 L- Telephone J 03SR\ D GRA\1lY (Ilms- 2 ) 1 D.AJ StatIon aems: tvby 1992 : ~ ~. U). ~. -.0 o ~ a;. 1m I I Gate On east side of terminal 4.0m South of v..all 1.Om Sourh of door 0.4m ast of wndow on concrete VvOIk\M:::ly GRA\AlY ST.All()\JS PlISlR,AUPl\J NAllQ\J,Al GRA\AlY NlV\ORK AGSO AUSTRALIAN GIIC1.OGICAL SlIMlY OI.CANIIATJON ~: :::0. ~ ~. ~. itt. ~. i f\) ~. f\)

14 MT WILLOUGHBY COBR PDY TI Station t Time Reading Latitude Longitude Comments TRAVRS TRAVRS L L APPNDIX 3 FILD OBSRV A TrONS MT WILLOUGHBY WINDSOCK COOBR PDY TRMINAL COOBR PDY WINDSOCK Australian Geological Survey Organisation GRAVITY NDFLGHT NDFLGHT NDGRAVS

15 8 APPNDIX 4 TIDAL GRAVITY CORRCIlONS MT WILLOUGHBY COBR PDY TI GRAVIT Y Page No. 1 Computed on 1996/ 09 / 06 Stat ion. Day Hrs Min Corr. rdg. Lat(deg. min) Long (deg.min) TRAVRS /92 132L GMT+ 8H OM S S S S S S S S S S S TRAVRS /92 252L GMT+ 8H OM S S S S S S S S S S S Co r r e ctio n(mgal) Australian Geological Survey Organisation

16 9 APPNDIX 5 PROCSSING SUMMARY AND STATISTICS. GRVHTS Version 6 of November Phase one sub-program Computed on 1996/09/06 at 11:44:54 ********** Input data for this pass being read from non-standard unit 40 Gravity meter data reduction Use new scale correction for LaCoste meters Latitude-Longitude data saved Segment identification *MT WILLOUGHBY COOBR PDY TI TRAVRS Flight /92 Meter 132L Scale factor Scale correction factor is Station Time Gravity Drift Ditf Reading TRAVRS Flight 1 22/ 5/92 Meter 252L Scale factor Scale correction factor is Station Time Gravity Drift Ditf Reading MNSLOP completed at 0.4 seconds. Position data saved on scratch file Position data transfer completed at 0.4 sec Scratch file closed GRAVITY * GRVHTS Version 6 of November 1992 Phase two sub-program Computed on 1996/09/06 at 11:44:55 Least squares adjustment phase - Number of segments to adjust together *MT WILLOUGHBY COOBR PDY TI Free nodes Fixed nodes Values commenced 0.4 sec Australian Geological Survey Organisation' GRAVITY *

17 Segment Free and fixed node lists compared Number of free nodes deleted is Final number of free nodes is Final number of fixed nodes is Total number of nodes in list is Maximum adjustment expected - Data search commenced Height Gravity Magnetic o sec identification *MT WILLOUGHBY COOBR PDY TI metres 1.00 mums gammas GRAVITY * TRAVRS ********** Internal loop - tied TRAVRS **.* Internal loop - tied to node to node from from reading reading 3 to reading 3 to reading 4 4 Linkage search commenced 0. 4 sec Matrix inversion commenced Matrix inversion completed 0.4 sec 0.5 sec Least squares values for free nodes node VALU Connection table and adjustments Node Node Difference Adjustment FIXD FIXD FIXD FIXD FIXD FIXD FIXD FIXD fl ight TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 TRAVRS 1 Standard deviation of adjustments Mean of adjustments 0.00 Maximum adjustment Number of lines in network 18 Flight data adjusted - starting 0.5 sec. Segment identification *MT WILLOUGHBY COOBR PDY TI Gravity differences scaled by 10.0 for micrometres Australian Geological Survey Organisation GRAVITY

18 Station list sort commenced Final sorted values *MT WILLOUGHBY C008R PDY TI NOD NOD NOD Number of stations in sorted list 3 Number of different stations 3 Station list sort completed sec 0.5 sec GRVHTS Version 6 of November 1992 Phase two sub-program Latitude-longitude insertion phase - Number of segments to merge 1 Segment identification TRAVRS TRAVRS Final position list checked Commenced *MT WILLOUGHBY COOBR PDY TI / /92 Merging of position data completed o Non-fatal mistakes discovered o Mis'si'ng positions in final lis,t o Fatal errors occurred in merging 0.6 sec GRVHTS Version 6 of November 1992 Phase two sub-program Creation of new segment file New output file created on unit 2 labelled *AUSTRALIAN GP~VITY DATA GRAVITY * Computed on 1996/09/06 at 11:44: sec LATLONG * Computed on 1996/09/06 at 11 : 44:56 ********** 3 Stations output in newly created segment on unit 2 labelled *MT WILLOUGHBY COOBR PDY TI New output file on unit 2 terminated labelled *AUSTRALIAN GRAVITY DATA 96/09/06* CRAT completed at 0.6 sec. AustrnIian Geological Survey Organisation 96/09/06* 96/09/06*