Survey Report

South Pacific Sea Level and Climate Monitoring Project (SPSLCMP)

EDM Height Traversing (Leap Frog Method) & Precise Differential Levelling Surveys.

TONGA June 2005

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Contents Page 1. Bench Mark Locality Map……………………………. 3 2. Introduction …………………………………………… 4 3. Equipment ………………………….. ……………….. 4 4. Method ………..………………………………………. 4 5. Route …………………………………………………... 5 6. Levelling Comparison and Table of Results ………… 6 7. Comparisons of Reduced Levels ……………………… 7 8. TONG RMs and TONGBM locality diagrams …….. 8 - 12 9. Deep Driven Bench Mark Diagrams ………………… 13 - 18

1. Bench Mark Locality Map

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2. Introduction This report outlines the surveys completed during the visit to Tonga, June 2005. Personnel: Steve Yates – Surveyor - GEOSCIENCE AUSTRALIA Andrick Lal – Surveyor - SOPAC As part of the South Pacific Sea Level and Climate Monitoring Project (SPSCLMP), Geoscience Australia has been requested to undertake the Levelling Survey of the Deep Bench Mark Array and SEAFRAME Station using both the Electronic Distance Measuring (EDM), Height Traversing, leap frog method and the Precise Differential Levelling techniques. This request was from the Australian Agency for International Development (AusAID), through the SPSLCMP manager, Australian Marine Science and Technology (AMSAT). The Levelling Comparison, Table of Results and the Comparison of Reduced Levels from the two techniques are listed on Pages 6 and 7. This survey was the first to be completed in Tonga using the EDM Height Traversing and the Precise Differential Levelling techniques. From the results of the two techniques a comparison will be determined and on subsequent scheduled Tongan visits, Geoscience Australia will perform the EDM Height Traversing Levelling method only. 3. Equipment

EDM Equipment LEICA Total Station Model TCA1800 (S/N 424936). LEICA Precision Prisms GPH1P (2). LEICA Rigid Tripod. Stainless Steel Target Poles supported by LEICA Bi-Poles (2). Shortened Stainless Steel Target Pole for the SEAFRAME Sensor BM Connection. LEICA Cast Iron Change Plates (2). KESTRAL 4000 Pocket Weather Tracker Digital Levelling Equipment LEICA Digital Level Model NA3003 (S/N 283676) LEICA Invar Staves, supported by telescopic Bi-Poles (2) LEICA Rigid Tripod. LEICA Cast Iron Change Plates (2). 4. Method The EDM Height Traversing and the Precise Differential Levelling methods were both performed to the Class L2A, as per the Inter-Government Committee on Surveying and Mapping (ICSM), Standards and Practices for Control Surveys, SP1, Ver. 1.5, May 2002. All observations for both techniques were recorded digitally. For the EDM Height Traversing method, atmospheric readings were obtained using a KESTRAL 4000 Pocket Weather Tracker. These atmospheric readings were recorded manually onto the Tongan Levelling Booking Sheets and entered into the Total Station prior to each level run and approximately every hour there after. For the Precise Differential Levelling method all observations were recorded manually, in the field, onto Field Levelling sheets.

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5. Route (refer to Bench Mark Locality Map Page 3) All the TONG Reference Marks, TONGBM and the Coastal Array Bench Marks were found undisturbed and in good order.* Levelling connections were made to: TON15 (The Project Plaque) TON16 (SEAFRAME Sensor bench mark). TON1 TON2 TON3 TON60 TON61 TON62 TONGBM and the 3 Reference Marks The Tonga Level Route (EDM Height Traversing Technique) started at TON1, which is held fixed and located at the intersection of Vuna Avenue and the By-Pass Road outside the entry road to the Queen Salote Wharf and proceeded along the road into the wharf area to the NTC Project Tide Gauge Plaque – TON15 and the SEAFRAME Sensor BM – TON16. The level route then recommenced at TON1 and went via the Deep Driven BM’s – TON60 (along the By-Pass Road) TON60 to TON61 (along the By-Pass Road) TON61 to TON62 (near Apifo’ou College) TON62 to TONGBM (inside Apifo’ou College grounds) TON61 to TON2 (along the By-Pass Road) TON2 to TON3 (along By-Pass Road) A total distance of 2.2 Kilometres. The Precise Differential Levelling technique followed the same route and also included all the existing holding marks previously placed by NTC. An internal precision of 1.0mm √K or better was achieved for both methods and for all sections levelled. *See the TONG Reference Mark and TONGBM locality diagrams on Pages 8 to 12 and the Deep Driven BM locality diagrams on Pages 13 to 18

6. Levelling Comparison and Table of Results

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7. Comparisons of Reduced Levels

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8. TONG RMs and TONGBM locality diagrams.

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8. TONGA Deep Driven Bench Mark Diagrams.

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