Correcting New Zealands longterm sea level records for

Correcting New Zealand’s long-term sea level records for tectonic uplift using continuous GPS observations Auckland Wellington Lyttelton Dunedin Toulouse 2002 Paul Denys John Beavan Dion Matheson Mikael Denham Chris Pearson John Hannah

AUCK & TAKL WGTN & WGTT MQZG & LYTT OUSD & DUNT • Sites with ~100 years of TG records • CGPS close or collocated with TG recorders • But … Problems … • TG sites not stable • Possible GPS masking problems • High multipath environments • Requires careful monitoring Paired CGPS and CGPS@TG sites Toulouse 2002

• Local stability: • Regional stability: TG pole/recorder to local benchmarks CGPS@TG to regional CGPS to CGPS@TG (km) TG to CGPS@TG (km) CGPS@TG to TG Connection Method Auckland 27. 3 Collocated Spirit level Wellington 4. 2 0. 55 Lyttelton 12. 1 Collocated Spirit level Dunedin 11. 1 0. 4 Spirit level + GPS Tide Gauge Site Stability Monitoring Toulouse 2002

Ports of Auckland Tide Gauge and TAKL CGPS Station • • • CGPS antenna (TAKL) Located on Captain Cook Wharf, Auckland Tide gauge measurement system uses microwaves reflected off sea surface beneath wharf Reference surface of tide gauge is immediately adjacent to base of GPS antenna Toulouse 2002 Tide Gauge mounted under this cover Base of antenna mast firmly bolted to wharf

Power Supply/ Battery charger GPS receiver Industrial PC on internet Back-up battery CGPS Receiver at Ports of Auckland Toulouse 2002

Automatic tide gauge Manual gauge Measuring system at Wellington float-type tide gauge Toulouse 2002

WGTT Continuous GPS Station Mast is attached through facing onto the main structural wall of the museum Toulouse 2002

Toulouse 2002

HEIGHT CONNECTION from WELLINGTON TIDE GAUGE BENCH MARK (TGBM) to CONTINUOUS GPS (WGTT) 1. Install Temporary GPS (WGTA) 1. 50 m from TGBM for 24 hours every 3 months 2. Same antenna type and radome used at WGTT and WGTA 3. Level TGBM and WGTA several times during 24 hour period 2. GPS Baseline Processing 1. Troposphere variation solved at WGTT as part of regional network processing 2. Same troposphere variation assumed at WGTA as at WGTT when solving for the WGTT - WGTA height difference 3. Another CGPS site, WGTN, is located in bedrock 5. 5 km from WGTT 1. Provides a check on the stability of WGTT Toulouse 2002

Location of WGTT CGPS (at Te Papa) Temporary GPS used to tie between tide gauge BM and WGTT GPS levelling: temporary GPS to WGTT CGPS Toulouse 2002

Temporary GPS used to tie between tide gauge BM and WGTT Level Precise levelling: Wellington tide gauge to temporary GPS Toulouse 2002

Precise and GPS levelling results: Wellington tide gauge Toulouse 2002

Combined geodetic and GPS levelling results Wellington tide gauge Toulouse 2002

Tide Gauge Hut and GPS antenna Structure Stability Problems: Wooden Wharf at Lyttelton Toulouse 2002

TG recorder and tide pole CGPS@TG site Port Chalmers: Poor GPS Environment Toulouse 2002

Regional Stability: CGPS to CGPS@TG Toulouse 2002

Baseline Distance (km) Latitude (mm) Longitide (mm) Height (mm) Velocity (mm/yr) OUSDDUNT 11. 1 1. 9 1. 8 5. 9 0. 6 MQZGLYTT 12. 1 4. 6 2. 5 4. 5 0. 7 WGTNWGTT 4. 2 2. 4 3. 6 5. 7 1. 2 AUCKTAKL 27. 3 1. 6 1. 8 6. 9 8. 8 rms of Baseline Components and Vertical Velocity Toulouse 2002

Sea. Leveltrue = Sea. Levelmeasured +/- ? ? ? Tide Gauge Mean Annual Sea Level Record: June 2002 Toulouse 2002

• CGPS installed at 4 long • CGPS to CGPS @TG stability record TG locations • CGPS collocated or within 600 m • Baselines 4, 11, 12 & 27 km • Horz rms 2 -3 mm (excluding MQZG-LYTT) • Site stability monitored using a variety of methods • Precise levelling to close BMs • GPS “levelling” to regional CGPS and TG BM • Vert rms 5 -7 mm • Vert vel ~1 mm/yr (excluding AUCK-TAKL) New Zealand’s CGPS @TG Project Toulouse 2002