12.540 Principles of the globa Positioning System Lecture 23 Pre of. thomas herring 12540Lec23 OVERVIEW Run through Hw 03 Final lecture: Application area and gPs results Analysis of contemporary motions in the Tien Shan region of central Asia Example of evolution of a network Issues faced when generating multi-year(decade) velocity model
05/12/03 12.540 Lec 23 1 12.540 Principles of the Global Positioning System Lecture 23 05/12/03 12.540 Lec 23 2 results – region of central Asia. – Example of evolution of a network – velocity model. Prof. Thomas Herring OVERVIEW • Run through HW 03. • Final lecture: Application area and GPS Analysis of contemporary motions in the Tien Shan Issues faced when generating multi-year (decade) 1
omework 03 Results from analyses Phase 22253288074676994950537115988548 Rinex file|-2225316719467699521413711599980 L1 only 2225401.05 4677074.26 371159632 LC data 222539555467706277 371158548 BKAP|-222543272467699479 371159945 Erwan 222568944676973873371193862 -222540287046770226263711614283 12540Lec23 Central Asia Analysis · Network Development of network Transition from"pins"with tripods to IVTRAN fixed-heights monuments Continuous stations Analysis methods Pre-continuous station analysis Merger with global GPS analyses Motion relative to eurasia Methods of used to realize a eurasia fixed frame Vertical motions Vertical motions as a function of existing topographic heights
Homework 03 Results from analyses: Phase -2225432.8807 -4676994.9505 3711598.8548 Rinex file -2225431.6719 -4676995.2141 3711599.9580 L1 only -2225401.05 -4677074.26 3711596.32 LC data -2225395.55 -4677062.77 3711585.48 Diff BKAP -2225432.72 -4676994.79 3711599.45 Erwan -2225468.944 -4676973.873 3711593.862 Lili -2225402.870 -4677022.626 3711614.283 05/12/03 12.540 Lec 23 3 05/12/03 12.540 Lec 23 4 Central Asia Analysis • Network monuments • Analysis methods • Motion relative to Eurasia • Vertical motions – Development of network – Transition from “pins” with tripods to IVTRAN fixed-heights – Continuous stations – Pre-continuous station analysis – Merger with global GPS analyses – Methods of used to realize a Eurasia fixed frame – Vertical motions as a function of existing topographic heights 2
Network First measurements made in July 1992: just after start of International GPS Service(IGS). Since then measurements each year and often multiple campaigns per year. The current network has over 1000 sites, many of them being ecovery marks for the main stations(typically 3 per locatio Network extends from Kyrgyzstan to the Kazakh Platform In 1995. the first continuously operating stations installed Currently, 9 continuous sites with 2 IGS sites(POL2, SELE) Results available on web at delay estimates) 12540Lec23 Regional view of network Zoom Eurasia Fixed ⊙ Frame realized TRF2000 50% confidence 05/1203 12540Lec23
Network • Development of Network – First measurements made in July 1992; just after start of International GPS Service (IGS). Since then measurements each year and often multiple campaigns per year. – The current network has over 1000 sites, many of them being recovery marks for the main stations (typically 3 per location) – Network extends from Kyrgyzstan to the Kazakh Platform – In 1995, the first continuously operating stations installed. Currently, 9 continuous sites with 2 IGS sites (POL2, SELE) – Results available on web at: http://www-gpsg.mit.edu/~tah/cont98g/cont98.html (Pages include time-series, phase residuals, atmospheric delay estimates) 05/12/03 12.540 Lec 23 5 05/12/03 12.540 Lec 23 6 Regional view of network Zoom Eurasia Fixed Frame realized using ITRF2000 50% confidence ellipses shown 3
Monument evolution Original monuments were mainly steel pins in bedrock which required tripod setups Starting in 1995: IVTRAN designed fixed-heights were installed. Simplified setup. Three recovery marks installed for each original monument After 1995, measurements made on the recovery marks rather than original marks With the original marks and fixed height marks, for many stations two independent velocity estimates (results shown later) 12540Lec23 Analysis methods Prior to 1995; selected IGS from Europe, Asia and Australia included in the analysis of regional data After 1995 when pol2 became an IGs site and was routinely included in the IGs analysis; only local sites included in the MIT analysis Using GAMIT/GLOBK; regional analyses are included in the Scripps Institution of Oceanography IGS (SOPAC)analysis including orbit improvement(more mportant in early data ftp: /garner. ucsd. edu/pub/hfiles Campaigns are combined with SOPAC h-files for velocity field and repeatability analys
05/12/03 12.540 Lec 23 7 Monument evolution • which required tripod setups • installed. Simplified setup. Three recovery marks installed for each original monument. • After 1995, measurements made on the recovery marks rather than original marks. • With the original marks and fixed height marks, for many stations two independent velocity estimates (results shown later) Original monuments were mainly steel pins in bedrock Starting in 1995: IVTRAN designed fixed-heights were Analysis methods • Prior to 1995; selected IGS from Europe, Asia and Australia included in the analysis of regional data • After 1995 when POL2 became an IGS site and was routinely included in the IGS analysis; only local sites included in the MIT analysis • Using GAMIT/GLOBK; regional analyses are included in the Scripps Institution of Oceanography IGS (SOPAC) analysis including orbit improvement (more important in early data). ftp://garner.ucsd.edu/pub/hfiles • Campaigns are combined with SOPAC h-files for velocity field and repeatability analyses. 05/12/03 12.540 Lec 23 8 4
Analysis Meth Types of analyses performed with combined files Velocity field analysis. Multiple types Global: Global selection of sites along with regional sites Eurasian frame then defined using the ITRF2000 Eurasian Eurasian: only sites from eurasia included. Eurasian frame defined to minimize velocities of stable eurasian sites In both analyses: Option to force velocities at nearby sites(<0.5 km separation) to be the same(some exceptions) slated to best alig time with positions and velocities from one of the velocity IVTRAN Monuments od length 355 Monument components antennas used in Central Asia 05/1203 12540Lec23
05/12/03 12.540 Lec 23 9 Analysis Method • Multiple types • Global: Global selection of sites along with regional sites. Eurasian frame then defined using the ITRF2000 Eurasian rotation pole. • Eurasian: Only sites from Eurasia included. Eurasian frame defined to minimize velocities of stable Eurasian sites • In both analyses: Option to force velocities at nearby sites (<0.5 km separation) to be the same (some exceptions) • Each campaign is rotated/translated to best align as a function of time with positions and velocities from one of the velocity analyses. Types of analyses performed with combined files: – Velocity field analysis. – Repeatability analysis: 05/12/03 12.540 Lec 23 10 IVTRAN Monuments Monument components Installed monument (SST antennas used in Central Asia Rod length 355 mm 5
Statistical analysis Since the network contains both continuous sites and campaign sites, we include statistical process noise in the velocity analyses to account for temporal correlations in the time series Each site has random walk process noise(2 mm)2ly Without process noise, velocities of continuous sites would have sigmas of 1 for global; sigmas depend on size of region considered
Statistical analysis • Since the network contains both continuous sites and campaign sites, we include statistical process noise in the velocity analyses to account for temporal correlations in the time series. • Each site has random walk process noise (2 mm)2/yr • Without process noise, velocities of continuous sites would have sigmas of 1 for global; sigmas 6
ITRF2000 Residuals RMS 0.8mm 12540Lec23 Eurasia only residuals 5 mm/yr 14 sites model at NYAL ONSA
05/12/03 12.540 Lec 23 13 ITRF2000 Residuals Horizontal RMS 0.8 mm/yr 52-sites 05/12/03 12.540 Lec 23 14 Eurasia only residuals Horizontal RMS 0.5 mm/yr 14 sites Postglacial rebound model at NYAL, ONSA 7
Difference between realizations z RMS Difference 1.3 mm/yr Set by systematic 1. 3 mm/yr E 0.7 mm/yr N If removed 0.1mm/ RMS 12540Lec23 Local frame realization Another method for frame realization is the use of local stations(1200x 1800 km region) in forming velocity solution The frame is then found by rotation/translation to best match the Eurasia only realization In this method, effects of global scale systematic errors should be reduced RMS difference of velocities is 0.4 mm/yr(vx2/f0.2) and only slightly changed by estimating rotation/translation between fields
05/12/03 12.540 Lec 23 15 Zoom RMS Difference 1.3 mm/yr systematic -1.3 mm/yr E -0.7 mm/yr N If removed 0.1 mm/yr RMS Difference between Realizations Set by 05/12/03 12.540 Lec 23 16 • Another method for frame realization is the use of velocity solution. • The frame is then found by rotation/translation to best match the Eurasia only realization • In this method, effects of global scale systematic errors should be reduced. • RMS difference of velocities is 0.4 mm/yr (√c2/f 0.2) and only slightly changed by estimating rotation/translation between fields. Local Frame realization local stations (1200x1800 km region) in forming 8
Local frame realization differences Zoom 12540Lec23 Differences between co-located sites Of the approximately 400 sites with high quality velocity estimates, 104 sites are collated between old and new monument styles Comparison Analysis Horizontal RMS 3D-RMS Global 1.9 mm/yr 2.5 mm/yr Regional 1.9 mm/yr 2. 4 mm/yr (V20.9) (V211) 05/1203 12540Lec23
05/12/03 12.540 Lec 23 17 Zoom Local Frame Realization Differences Differences between co-located sites • Of the approximately 400 sites with highquality velocity estimates, 104 sites are collated between old and new monument styles. • Comparison: Analysis Horizontal RMS 3D-RMS Global 1.9 mm/yr (√c2/f 1.0) 2.5 mm/yr (√c2/f 1.1) Regional 1.9 mm/yr (√c2/f 0.9) 2.4 mm/yr (√c2/f1.1) 05/12/03 12.540 Lec 23 18 9
Collocated velocity estimates 50% confidence intervals Differences with sigmas 12540Lec23 Motion in eurasia frame Motion from difference Best estimates Site East POL20.5±0.63.0±0.6 SELE0.9±0.83.7±0.8 AzoK1.2±0.91.1±0.9 cHUM-03±1.004±1.0
05/12/03 12.540 Lec 23 19 Collocated velocity estimates Zoom 50% confidence intervals Differences are consistent with sigmas 05/12/03 12.540 Lec 23 20 Motion in Eurasia Frame Motion from difference analyses Best Estimates: Site East North mm/yr mm/yr POL2 3.0±0.6 SELE 0.9±0.8 3.7±0.8 AZOK 1.2±0.9 0.5±0.6 1.1±0.9 CHUM -0.3±1.0 0.4±1.0 10
