Ray‐traced tropospheric delays in VLBI analysis

Nafisi, Vahab; Madzak, Matthias; Boehm, J.; Ardalan, Alireza A.; Schuh, Harald

doi:10.1029/2011rs004918

Cited by 35 publications

(24 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore the Vienna ray-tracer was applied through the pressure level data to obtain tropospheric delays for different elevation angles. A more detailed description of the Vienna ray-tracer can be found in [16].…”

Section: Validation By Ray-tracingmentioning

confidence: 99%

Improved Troposphere Blind Models Based on Numerical Weather Data

2014

Self Cite

View full text Add to dashboard Cite

The troposphere blind model RTCA MOPS is the minimum operational performance standard for global positioning systems. With a standard deviation of 2.3% of the ZTD, it enables us to mitigate the main part of the tropospheric effect on GNSS signals. Nevertheless, the comparison of RTCA MOPS with modern troposphere models like the ESA model or GPT2 shows the limitation of RTCA MOPS and points out the potential of modern troposphere blind models based on climatological series derived from numerical weather data. The ESA model profits from a more advanced wet delay model and a higher spatial resolution. GPT2 shows the smallest mean bias on surface level in comparison to ray‐tracing and IGS data and profits from additional mapping function coefficients – especially if the user is interested in tropospheric delay at low elevation angles. A revision of GPT2 ‐ called GPT2w ‐ combines the benefits of both aforementioned models. Copyright © 2014 Institute of Navigation.

show abstract

Section: Validation By Ray-tracingmentioning

confidence: 99%

Improved Troposphere Blind Models Based on Numerical Weather Data

2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…As formulated, the signal travel time delay is computed for a transmitter with a finite distance to the receiver. In another space geodetic technique, i.e., very long baseline interferometry (VLBI) [see, e.g., Nafisi et al , ], the transmitter is practically at an infinite distance to the receiver. This is accounted for through

\begin{matrix} alignleft \\ align-1 y_{0} & align-2 = 0 \\ align-1 y_{m + 1} & align-2 = y_{m} \end{matrix}

and guarantees that the tangent vector of the signal path is parallel to the tangent vector of the geometric path at the hypothetical top of the atmosphere.…”

Section: Technical Descriptionmentioning

confidence: 99%

“…However, at that time we utilized different NWM input data. Here, we restrict the comparison to those participants utilizing the same NWM input data: KARAT [ Hobiger et al , ], UNB [ Urquhart , ], and VIE [ Nafisi et al , ].…”

Section: The Performancementioning

confidence: 99%

See 1 more Smart Citation

The rapid and precise computation of GPS slant total delays and mapping factors utilizing a numerical weather model

et al. 2014

View full text Add to dashboard Cite

In a previous study we developed an elegant technique to compute the signal travel time delay due to the neutral atmosphere, also known as slant total delay (STD), between a Global Positioning System (GPS) satellite and a ground‐based receiver utilizing data from a numerical weather model (NWM). Currently, we make use of NWM data from the Global Forecast System (GFS) because short‐range forecasts are easily accessible. In this study we introduce some modifications which double the speed of our algorithm without altering its precision; on an ordinary PC (using a single core) we compute about 2000 STDs per second with a precision of about 1 mm. The data throughput and precision are independent of the vacuum elevation (azimuth) angle of the receiver satellite link. Hence, the algorithm allows the computation of STDs in a mesobeta‐scale NWM with an unprecedented speed and precision. A practical by‐product of the algorithm is introduced as well; the Potsdam Mapping Factors (PMFs), which are generated by fast direct mapping utilizing short‐range GFS forecasts. In fact, it appears that the PMFs make the application of parameterized mapping in GPS processing obsolete.

show abstract

“…Investigations on the accuracy of different practical implementations of the ray-tracing method have been carried out by Hobiger et al (2008); Nafisi et al (2012a); Hofmeister (2016).…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Application of ray-traced tropospheric slant delays to geodetic VLBI analysis

Hofmeister

Boehm

2017

J Geod

Self Cite

View full text Add to dashboard Cite

The correction of tropospheric influences via socalled path delays is critical for the analysis of observations from space geodetic techniques like the very long baseline interferometry (VLBI). In standard VLBI analysis, the a priori slant path delays are determined using the concept of zenith delays, mapping functions and gradients. The a priori use of ray-traced delays, i.e., tropospheric slant path delays determined with the technique of ray-tracing through the meteorological data of numerical weather models (NWM), serves as an alternative way of correcting the influences of the troposphere on the VLBI observations within the analysis. In the presented research, the application of ray-traced delays to the VLBI analysis of sessions in a time span of 16.5 years is investigated. Ray-traced delays have been determined with program RADIATE (see Hofmeister in Ph.D. thesis, Department of Geodesy and Geophysics, Faculty of Mathematics and Geoinformation, Technische Universität Wien. http:// resolver.obvsg.at/urn:nbn:at:at-ubtuw:1-3444, 2016) utilizing meteorological data provided by NWM of the European Centre for Medium-Range Weather Forecasts (ECMWF). In comparison with a standard VLBI analysis, which includes the tropospheric gradient estimation, the application of the ray-traced delays to an analysis, which uses the same parameterization except for the a priori slant path delay handling and the used wet mapping factors for the zenith wet delay (ZWD) estimation, improves the baseline length repeatability (BLR) at 55.9% of the baselines at sub-mm level. If no tropospheric gradients are estimated within the compared analyses, 90.6% of all baselines benefit from the application of the ray-traced delays, which leads to an average improvement of the BLR of 1 mm. The effects of the ray-traced delays on the terrestrial reference frame are also investigated. A separate assessment of the RADIATE ray-traced delays is carried out by comparison to the ray-traced delays from the National Aeronautics and Space Administration Goddard Space Flight Center (NASA GSFC) (Eriksson and MacMillan in http:// lacerta.gsfc.nasa.gov/tropodelays, 2016) with respect to the analysis performances in terms of BLR results. If tropospheric gradient estimation is included in the analysis, 51.3% of the baselines benefit from the RADIATE ray-traced delays at sub-mm difference level. If no tropospheric gradients are estimated within the analysis, the RADIATE ray-traced delays deliver a better BLR at 63% of the baselines compared to the NASA GSFC ray-traced delays.

show abstract

Ray‐traced tropospheric delays in VLBI analysis

Cited by 35 publications

References 55 publications

Improved Troposphere Blind Models Based on Numerical Weather Data

Improved Troposphere Blind Models Based on Numerical Weather Data

The rapid and precise computation of GPS slant total delays and mapping factors utilizing a numerical weather model

Application of ray-traced tropospheric slant delays to geodetic VLBI analysis

Contact Info

Product

Resources

About