SRI Seminar 2005

Time series of GPS stations

For reference, monitoring and geophysics

Günter Stangl

Federal Office of Metrology and Surveying

SRI Seminar 2005

Some Definitions

GPS = Global Positioning System 2 Frequencies (Between 1-2 GHz) Phase measurements (L1,L2) for

precise determination, resolution about 0.5 mm

Equipment antennas+receivers Post processing for high accuracy

SRI Seminar 2005

Some more Definitions

ITRS = International Terrestrial Reference System (Earth fixed system)

ITRF = Representation of ITRS, updated sometimes, presently ITRF2000 (epoch 1997.0), combined solution of VLBI, SLR, GPS and DORIS measurements

ETRS89 = European Terrestrial Reference System (Fixed to the “stable“ part of Eurasia, defined 1989), plate velocity removed, “constant” coordinates

ETRF = Representation of ETRS, derived from ITRF by GPS, Helmert transformation applied

SRI Seminar 2005

Time Series

Coordinates derived from controlled adjustments (orbits fixed)

X,Y,Z transformed to φ, λ, h Differences in N(orth), E(ast), U(p) Neglecting correlations in space and time Restricted to permanent stations Total zenith delays for climatology (In Europe

standardized) Main target: station velocities (needed for ITRF

definition) Additional use for station monitoring (jumps) and

geodynamics (plate motions)

SRI Seminar 2005

Different Reference Frames Different Antenna Definitions Modeling Errors Seasonal Variations Site Problems (Equipment,

Monumentation, Atmosphere) Orbits and Clocks before 1992 Orbits and Clocks 1992-2004 Different Adjustments

About 20 mm About 10 mm About 5 mm Up to 10 mm Up to 30 mm Height 60 mm About 50 mm Up to 30 mm Up to 20 mm

Systematic effects on station coordinates

SRI Seminar 2005

Removing procedures

Reference frame transformation (identical sites)

Recomputation with calibrated antenna values

Recomputation with corrected orbits

Combined adjustment solutions Detrending (velocities)

SRI Seminar 2005

IGS station map

SRI Seminar 2005

EPN station map

SRI Seminar 2005

IGS station velocity map

SRI Seminar 2005

NUVEL (2D) Plate Motions derived from geology

SRI Seminar 2005

Example BahrainITRF2000 (1995-1999)

SRI Seminar 2005

Example BahrainITRF2000 short term

North East Up

SRI Seminar 2005

Example GrazITRF2000

SRI Seminar 2005

Example AnkaraETRS89 reference jumps removed

SRI Seminar 2005

Example GrazETRS89 detrended + reference jumps removed

SRI Seminar 2005

Example AnkaraETRS89 detrended + reference jumps removed

SRI Seminar 2005

Earthquake Signal

Earthquake shift

some decimeters

SRI Seminar 2005

Pseudo-Earthquake Signal

Receiver change and earthquake nearby

SRI Seminar 2005

Equipment Effects

SRI Seminar 2005

Periodic Effects

SRI Seminar 2005

Examples from Austria

+ 20 stations from

Germany, Slovenia, Switzerland

+ 5 new stations/year

SRI Seminar 2005

HFLK (Hafelekar )Monumentation in bedrock

Permanent since October 1994, constructed by ZAMG Wien

1994: Minirogue 1997: Turborogue 1999: Trimble Software: Terrasat

Permanentstation for: IGS since 1994 EPN since 1996 APOS RTK since 2004

SRI Seminar 2005

RTMN (Rottenmann)Monumentation on building

Permanent since September 1999; financed by city of Rottenmann

9/1999: Trimble 11/1999: Z-18 Software: Terrasat

SRI Seminar 2005

Local Effects (1)

Danube Alluvium

Gradual sinking

SRI Seminar 2005

Local Effects (2)

Rock instability

Overlay of seasonal

(frost) and rock gliding effects ?

(Station height 3 600 m)

SRI Seminar 2005

Human Errors and Strange Effects

Probably Snow/Ice

But wrong direction

?My failure

wrong antenna type

SRI Seminar 2005

Interpolation (1)Stress Field

SRI Seminar 2005

Interpolation (2)Strain Field

SRI Seminar 2005

Summary Space Domain

Remove outliers and movements for reference determination

Remove outliers and reference jumps for velocity estimation

Remove outliers, reference jumps and known global velocities for regional (intraplate) motions

Remove all known features and you‘ll find new ones (?)

Which colour has the noise?

SRI Seminar 2005

Spectral Analysis (1)Autocorrelation

SRI Seminar 2005

Spectral Analysis (2)Power spectrum GRAZ

SRI Seminar 2005

You can have white noise coordinates!

Possible sources of non-white noise: - Receiver misbehaviour (Channels) - Adjustment procedures (models, orbits) - Monumentation (temperature, ice) - Underground (´water level) - Unmodelled weather effects (Foehn)

Summary Frequency Domain

SRI Seminar 2005

We will continueThank You!