retreat 2015 28.04.-30.04. miesenbach daniel landskron - my previous and upcoming research...

Retreat 2015 Daniel Landskron

Retreat 2015 28.04.-30.04.Miesenbach

Daniel Landskron-

My previous and upcoming research

12015/04/28

Retreat 2015 Daniel Landskron 2

Overview

Work together with Armin and Johannes

• Calculating tropospheric delays through ray-tracingcarried out by Armin‘s ray-tracing program RADIATE

• Modeling of tropospheric delays o Mapping functions

- site-augmented improvement of GPT2w

- temporal improvement of VMF1

o Azimuthal asymmetry

- new treatment of gradients

2015/04/28


Part 1

Part 1:

Research in Mapping Functions

2015/04/28


Improvement of GPT2w

2015/04/28

ah vs. T plot for WETTZELL 2011

Shows a clear correlation

If the user measures T => improve ah



2015/04/28

If user measures also e => improve zwd

zwd vs. e plot for WETTZELL 2011

Shows a clear correlation



2015/04/28

Comparison of mfh for WETTZELL first half of 2011, T from NWM



2015/04/28

Mapping Function

Δshd [cm] T (NWM)

Δzwd [cm]T (NWM)

GPT2w 1.3 2.6Additional

measurement of T 0.9 2.5Additional

measurement of T, e 0.9 1.7

Comparison slant hydrostatic delays w.r.t. VMF1:e = 5°; averaged for 18 VLBI stations from 2011-2014, zwd from ECMWF

=> GPT2w well suited for site-augmented approach using in situ measurements of

T, p and e

D.Landskron

shd can only be improved by T, e brings no further improvement



2015/04/28

Geographical variation of the coefficient M2


Improvement of VMF1 (1)

Calculation of new mapping function coefficients:

• For CONT11

• From ray-traced delays using RADIATE

=> No clear improvement in BLR

2015/04/28

D.Landskron

dazusagen, dass verschiedene Ansätze ausprobiert wurden, also einerseits empirische Werte für b,c und a dann in einem AUsgleich berechnet, andererseits a,b,c gemeinsam in einem AUsgleich (hier Probleme!)



Higher temporal resolution of NGS data

2015/04/28



2015/04/28


Part 2

Part 2:

Research in Azimuthal

Asymmetry

2015/04/28


Azimuthal asymmetry

Standard gradient formula (Chen and Herring, 1997):

Tropospheric delays vary for different azimuths because

• Atmosphere thicker at the equator

• E.g. weather fronts affect delay

Effect is significant for low-elevation observations

2015/04/28

D.Landskron

...therefore a ray travels longer through the atmosphere to Vienna if it comes from the South rather than from the north

D.Landskron

erklären: "delta L0(e) is the isotropic part of the delay, that is zenith delay times mapping function, while the rest describes the anisotropic part which is dependent on the azimuth

D.Landskron

the first point is a systematic delay and the second point is mostly random delay

D.Landskron

but can be neglected for observations ~ >15°


Azimuthal asymmetryNew gradient formulas:

2015/04/28

WESTFORDResiduals of total slant delays

D.Landskron

we introduced a gradient formula which is the original formula extended by a higher order term in the azimuthbecause the systematic delay can thus be better described

D.Landskron

einfach grob ein bisschen erklären was man auf den 4 Plots siehtgradient formula 1 describes ~70% of the residualsgradient formula 2 describes ~80% of the residualsgradient formula 1 describes only ~2% more of the residuals


Azimuthal asymmetry

Gradient formulas can be used:

1. as a priori gradients– gradients determined for every NWM epoch and provided in a text file

– use of the new gradient formulas improves the resulting delays

2. for estimating gradients in VLBI analysis– in vie_lsm, together with zwd, station coordinates, source coordinates,..

– Use of the new gradient formulas does not yield improvement

2015/04/28

D.Landskron

most likely because too many correlated parameters are estimated simultaneously


Azimuthal asymmetry

2015/04/28

A priori gradients (a) (b)none 1.20 1.07

standard gradient formula 1.10 1.05

extended formula (1) 1.09 1.03

extended formula (2) 1.09 1.04

BLR comparison for CONT11 in [cm]:(a) Only using a priori gradients(b) Additionally estimating gradients using standard gradient formula


Part 3

Part 3:

teaching activities

2015/04/28


Teaching activities

• 124.026 “Geodetic Space Techniques - project handling and data processing“ exercise

– takes place every even winter semester

– group work

– scheduling and Simulation in VieVS

– final presentation of the results

• Willingness to do more teaching

2015/04/28

D.Landskron

alternately a VLBI and a GNSS project

D.Landskron

groups to 3 people

D.Landskron

...and then comparing BLR and station coordinate repeatabilities

D.Landskron

I was content, nobody failed


Part 4

Part 4:

Outlook

2015/04/28


Outlook

• Collaboration with Gregor

• Find a way to map delays below 3° elevation as well

• Make everything operational, include in VieVS

• Make research for longer time periods

• Find a way to provide gradients on a grid

2015/04/28

D.Landskron

because the improved GPT2w can also be used with wet delays from GNSS PPP

D.Landskron

because the nowadays used mapping function formula is only valid for elevations above 3°

D.Landskron

so that everybody can make use of the research that we've done

D.Landskron

...as Armin is transferring his ray-tracing program to FORTRAN and thus creating simulated ray-traced delays for the whole VLBI historythat is, in the first line, calculation of new mapping functions

D.Landskron

quite tricky, but at least for the systematic part (variable thickness of the atmosphere) of the north gradient it must be possible

retreat 2015 28.04.-30.04. miesenbach daniel landskron - my previous and upcoming research...

Documents

daniel landskron420150428ah

daniel landskronoverviewwork

daniel landskron1420150428

daniel landskron220150428part

daniel landskron1220150428

clear improvement

ah improvement of gpt2wretreat

augmented improvement