New Coordinates for CORS Sites &Oregon Case Study

The NGS Multi-Year CORS Solution and the evolution from NAD 83(CORS96)Epoch 2002

toNAD 83(2011)Epoch 2010

ODOT Surveyors ConferenceMar 29th, 2011

By Mark L. Armstrong, PLS – NGS Oregon AdvisorMYCS slides from Dr. Jake Griffiths, Dr. Giovanni Sella and the MYCS Team at

NOAA/NGSOPUS-Net info. From Dr. Neil Weston

A Little History• ‘Multi-year’ effort began 5 years ago

• IGS proposed re-processing all data to re-compute station coordinates, orbits and EOPs from 1994-present• MYCS positions were derived from the

reprocessing of the full 16 year time series (1994-2010) and a rigorous stacking of weekly estimates in a fully consistent, global framework.

• 11 of these MYCS stations are in Oregon

• NAD 83(2011)Epoch2010 is a new realization of NAD 83 based on this NGS Multi-Year CORS Solution (MYCS)

Why Reprocess?Generally can’t continue to live in epoch 2002

• Generate fully consistent orbits, EOPs and CORS+global station coordinates using latest models and methods—existing history is inadequate for modern realizations of TRFs

– longer data spans– absolute antenna calibrations

• satellite transmitting and ground receiving antennas– new network design—added redundancy

• Delaunay triangulation over global sites and CORS backbone• tie remaining CORS to backbone as stars

– IERS 2003 Conventions generally implemented– updated model for station displacements due to ocean tidal loading– updated models for troposphere propagation delays– use current frame; first attempt to obtain a full history of products in a fully consistent

framework

• Contribute NGS reprocessed orbits, EOPs and global SINEX files to International GNSS Service (IGS) repro1 campaign

• Generate CORS coordinates and velocities in global framework using new orbits, EOPs and global station coords

Slide by J. Griffiths and the MYCS Team

Frame Definition and Nomenclature• ITRF frame (global) multi-technique—vlbi, slr, doris, gnss• IGS frame (global) GNSS only• NAD frame (plate fixed) related to ITRF• Critical to pay attention to frame tags and epoch dates and

antenna calibration values

Frame Name Epoch Antenna PCV* Data DurationITRF2000 1997.0 RelANTEX 1994.0-2002.0 ITRF00(NGS’ssoln) 1997.0 RelNGS ANTEX 1994.0-present

NAD 83(CORS96) 2002.0 RelNGS ANTEX 1994.0-presentITRF2008 2005.0 Abs IGS05 ANTEX 1997.0-2009.5IGS08 2005.0 Abs IGS08 ANTEX 1997.0-2009.5IGS08 (NGS’stentative) 2005.0 Abs IGS08 ANTEX 1994.0-2010.5(ongoing)NAD 83(2011) (tentative) 2010.0Abs IGS08 ANTEX 1994.0-2010.5 (ongoing)

Slide by J. Griffiths and the MYCS Team

West Coast Crustal Motion

Horizontal velocities in the western U.S.relative to the North American Datum of 1983 as derived from geodetic observations.

Slide from R. Snay, NGS

-Times 8 years (2002-2010)-As will be seen realized with NAD 83(2011)Epoch2010 (tent. name)

What now?

• Reprocessing and ITRF re-alignment may take place again in 5-6 years

• NAD 83(2011)Epoch2010 may be rolled into OPUS via an improved OPUS engine (OPUS-net)?

• 2011 [CORS96a] positions are an improvement over CORS96 positions– Case Studies- NC, SC, AR, OR

OPUS-Static vs. OPUS-Net (engines)• OPUS-Static

– U.S. CORS Network– Fixed IGS ephemerides

– Computes independent double differenced baseline solutions between the unknown and 3 CORS

– Relative antenna models– Phase ambiguity integer

fixing– Relative troposphere

modeling– ITRF2000 reference

frame– Average position

solution– Peak – Peak error

reported

• OPUS-Net– U.S. CORS Network & IGS

Global Network– Network approach

– Consists of 3 nearby CORS + up to 12 CGPS from global IGS network

– Absolute antenna models– SV & ground

– Ocean tidal loading model

– Satellite weighting– Relative troposphere

modeling– ITRF2008 reference

frame– Weighted least squares

adjustment – Weighted mean and

standard deviations reported at 95%

OPUS-net info. From Dr. Neil Weston

NGS Multi-Year CORS Solution (MYCS)A Case Study in Oregon

A comparison of how well the MYCS (CORS96a) coordinates fit in a network adjustment compared to

CORS96 coordinates

MYCS: NAD 83(CORS96a)Epoch 2010vs.

Published Datasheet (NGSIDB): NAD 83(CORS96)Epoch 2002

andOPUS-S Solution Mean (August 1-10, 2010):

NAD 83(CORS96)Epoch 2002

• The network adjustment tests performed were an attempt to provide an independent comparison of the MYCS positions of eleven CORS stations against both the published datasheet positions (NGSIDB) and concurrent (same ten days August 1-10, 2010) averaged OPUS-Static solutions.

SITE LATITUDE (N) LONGITUDE (W) HT Vx Vy Vz

BURN 42 46 46.188550 117 50 36.651830 1181.5006 1.99 3.16 -0.06

CABL 42 50 9.943030 124 33 47.986070 38.2843 11.93 3.47 10.9

CHZZ 45 29 11.441140 123 58 41.183650 51.1570 13.26 1.68 6.91

CORV 44 35 7.913010 123 18 16.516930 107.4991 8.44 2.78 4.88

DDSN 43 7 7.633560 123 14 39.212080 953.5800 5.03 5.05 5.59

FTS1* 46 12 17.581460 123 57 21.878600 -13.6069 13.7 -1 7.59

MDMT 42 25 6.013880 121 13 17.707890 1711.0742 1.6 4.26 3.54

NEWP* 44 35 6.075350 124 3 42.733130 22.1936 12.37 1.39 7.15

ORK1* 42 17 19.718270 121 40 9.541170 1258.6986 1.52 1.86 5.72

ORK2* 42 17 19.705200 121 40 10.701370 1258.6674 0.78 3.55 4.67

ORS1 44 9 51.274000 119 3 31.460480 1438.1199 3.06 2.24 1.28

ORS2 44 9 50.882490 119 3 30.350220 1439.0132 3.3 2.44 1.11

P367 44 35 6.873050 124 3 41.595930 23.2790 12.2 2.53 6.52

P376 44 56 28.315860 123 6 8.099260 181.2334 8.52 2.65 4.81

REDM 44 15 35.146710 121 8 52.314910 920.3443 4.47 2.99 1.73

* Stations in red no longer exist

Oregon Case Study cont.

• Baseline Processing– All baselines were processed, loop closures completed and

then the project was saved and copied to 3 separate projects before continuing forward with the network adjustments in each of three NAD 83 datum realizations identified in the introduction.

• Baselines that did not meet the loop closure requirement (0.030m horiz. and 0.050m vert.) were disabled. For the purposes of this investigation, performing the loop closure analysis provided informative statistics on the baseline vector interrelationships.

MYCS in Oregon

Final Computed MYCS CORS in Oregon

- Will be held fixed in adjusting the ORGN

Oregon CORS & CGPS

~31 CORS in Oregon~139 CORS + CGPS -11 MYCS CORS

ResultsDiagram shows plots of average error for 5 points constrained for each of the three realizations. The MYCS coordinates fit the baselines observed much better than the other two.

Results – MYCS Network Adj. with 5 points constrained

How does this affect Oregon CORS users?What changes will you see?

West Coast Crustal Motion

Horizontal velocities in the western U.S.relative to the North American Datum of 1983 as derived from geodetic observations.

Slide from R. Snay, NGS

-Times 8 years (2002-2010)-As will be seen realized with NAD 83(2011)Epoch2010 (tent. name)

NAD 83(2011)Epoch 2010How will you cope with the change?• The ORGN Real-time Network may shift to this new NAD 83

realization sometime toward end August 2011?• For ACTIVE projects how will you cope?

– Single base RTK from legacy project control?– Calibrate (localize)? – Shift your control to the new datum realization using OPUS-

Net?– Convert your control coordinates with the OPUS Datum

Conversion Tool for Oregon – • Currently under development and testing by Michael

Olsen and ODOT

Questions• Mark Armstrong, PLS - Geodesist• Oregon Advisor - NOAA/NOS/National Geodetic Survey• Office: Oregon Department of Transportation

Geometronics Unit4040 Fairview Industrial Dr. SE, Salem, OR 97302

• 503.986.3775 Office• 503.986.3548 Fax• 202.306.6716 Blackberry• Email: mark.l.armstrong@noaa.gov