H. van der Marel

Comparison of GPS slant delay measurements to a numerical model: case study of a cold front passage

Abstract GPS water vapour measurements are expected to have the ability to fill the lack of moisture information in numerical weather prediction (NWP) and nowcasting. Zenith total delays (ZTD) are obtained by mapping signal delays in the line of sight to the vertical in the processing of the GPS data. The estimated zenith integrated water vapour (IWV) can be extracted from this ZTD when surface pressure and temperature is available. This method is valid under the assumption that the atmosphere is layered and horizontally stratified. When a cold front passes the observation sites, this assumption is not valid. In this paper a case study of such a cold front passage is examined. Slant delays from GPS and the high resolution NWP model High Resolution Limited Area Model (HIRLAM) are derived, and the non-stratified slant wet delay components from GPS are compared with HIRLAM. Furthermore, GPS derived zenith IWV measurements are compared to HIRLAM. Meteosat water vapour channel information together with IWV derived from GPS and HIRLAM are used for interpreting the results. The additional information of slant measurements for use in synoptic forecasting and NWP is briefly discussed.

The proof of concept for 3-cm Altimetry using the Paris Interferometric Technique

A proof-of-concept instrument for PARIS-IOD, based on a full-custom dedicated GNSS-Reflections receiver has been developed, and the novel interferometric concept tested in several experiments using signals generated by a SPIRENT equipment. The preliminary analysis has resulted in the detection of 1-cm delay-jumps, using 33 group-delay observables of 1 second, with an associated dispersion of the order of 2-cm. A signal-to-noise degradation of the order of ∼3 dB with respect to the one expected for the Bridge Experiment would keep the 1-second sigma error below 3-cm. A second experiment using real reflected signals obtained from a relatively high bridge (∼15 m) over estuary waters is planned for July 2010. The aim of the activity is to confirm the PARIS Interferometric Technique concept as an altimetric system able to provide 3-cm resolution, as initially suggested by the presented preliminary results.

Use of Global and Regional Ionosphere Maps for Single-Frequency Precise Point Positioning

This paper compares global and regional ionosphere maps in different aspects, from vertical TEC and slant TEC in the range domain to their application in single-frequency Precise Point Positioning. Under quiet ionospheric conditions, the mean of the difference in vertical TEC between the global (GIM) and regional (SWACI) map, in Europe, was found to be less than 1 TECU, and the RMS generally in the order of 1–2 TECU. Both static data and kinematic (flight) data are analysed. Although being limited in its coverage for the moment, the real-time regional map SWACI (from DLR) provides promising results also with highly kinematic data. It is shown that for the dataset under investigation the SWACI map can bring the vertical positioning accuracy to the same level as the horizontal one, at 2–3 km (95% level)

Real-time GPS and GLONASS integrity monitoring and reference station software

Abstract At Delft University of Technology (DUT) a software suite has been developed for Continuously Operating GPS/GLONASS Reference Stations. The most important features of this software suite are a real-time GPS receiver interface, real-time integrity monitoring and communication with a computing centre. The sample rate of the receiver and the transmission rate to the computing centre can be selected independently, and the data are sent in discrete batches of several minutes up to 24 hours, or continuously. The data are stored on the local computer disk with the receivers sample rate. The real-time quality control and integrity monitoring is based on a single channel approach. It uses a Kalman filter based Detection, Identification and Adaptation (DIA)-procedure. Presently, the AOA Turbo Rogue, JPS Legacy, Trimble 4000SSE/SSI and Trimble 4700 receivers are supported. The software also includes an interface for meteorological sensors. The software has been used since 1997 for the Dutch Permanent GPS Network and since 1999 for DUTs IGEX GPS/GLONASS reference station.

Overview of Research and Networking with Ground based Remote Sensing for Atmospheric Profiling at the Cabauw Experimental Site for Atmospheric Research (CESAR) - The Netherlands

CESAR, the Cabauw Experimental Site for Atmospheric Research, is the Dutch focal point for collaboration on climate monitoring and atmospheric research and is situated on the KNMI meteorological research site near Cabauw in the Netherlands. CESAR addresses challenging topics in atmospheric research, especially the questions that are related to the interaction between clouds, aerosols and radiation and questions dealing with land-atmosphere interaction. These topics are approached via process studies, model evaluations, climate monitoring, development of new experimental techniques and supporting activities for satellite missions. For each of these approaches, specific demands are put on the instrumentation, mode of operation and overall infrastructure. This paper gives an overview of CESAR that was recently augmented with a scanning drizzle radar (IDRA) and a multi-wavelength Raman lidar for aerosols, clouds and water vapor (CAELI).

Electric quadrupole orientation of 188, 189Ir in graphite

Abstract Samples of 188 Ir and 189 Ir in foils of highly oriented pyrolytic graphite (HOPG) were obtained by electron capture decay of 188 Hg and 189 Hg nuclei, which were implanted at room temperature with the aid of the ISOLDE III facility. Nuclear electric quadrupole interaction of these Ir isotopes has been observed with the technique of low temperature nuclear orientation. With the known value for the quadrupole moment of 188 Ir, the electric field gradient of ir in HOPG was determined to be V zz = +9.96(28)× 10 22 V/m 2 . This gain could be used to determine the quadropolemoment Q ( su 189) Ir ) = + 0.79(6) b . The quadrupole interaction is so strong that at 10 mK the fraction f of nuclei at good sites aligns completely. There is no sign that the remaining part does align even at the lowest temperatures. The fraction f is 8.9(2)% for 188 Ir and 15.5(5)% for 189 Ir. These low values are supposedly caused by: i) lattice damage due to implantation or already existing; ii) partial occupation of positions between the graphite layers; and iii) perturbations due to preceding electron capture decay. Spin and mixing ratios concerning the 1575, 1716 and 2050 keV transitions of 188 Ir and of the 276 and 233 keV transitions of 189 Ir are reported.

Exploitation of Ground Based GPS for Numerical Weather Prediction and Climate Applications in Europe

The operational potential of ground-based GPS data to the fields of climate and Numerical Weather Prediction (NWP) is demonstrated in the European COST-716 action. The best way hitherto for NWP is to assimilate Zenith Total Delay (ZTD), but in order to be useful the estimates must arrive within 1 hour and 45 minutes.

Statistical Testing and Quality Analysis in 3-D Networks (part II) Application to GPS

In this paper reliability measures for geodetic networks with GPS measurements are discussed. Particular attention is given to the type of alternative hypotheses to be selected in order to get a realistic and meaningful concept of internal- and external reliability. For classical surveying networks it is often sufficient to consider only the so-called conventional alternative hypotheses, however, this is not true for GPS.

Proposal for a binary receiver independent exchange format

Abstract The Receiver Independent Exchange (RINEX) format can be considered as the de facto standard for storing and exchanging GPS and GLONASS data. It is, however, not suited for real-time applications and applications that require a high sample rate, due to its ASCII format. In this paper a new, binary receiver independent exchange format is proposed for both GPS and GLONASS. Software to test the new format is freely available from Delft University of Technology.

Nuclear electric quadrupole interaction of 182Re (64h) and 183Re recoil-implanted into graphite

Abstract The technique of static low-temperature nuclear orientation has been used to investigate the nuclear electric quadrupole interaction of implanted 182Re (64h) and 183Re in thin foils of highly oriented pyrolytic graphite (HOPG) at temperatures down to 5 mK. The isotopes were recoil-implanted at a temperature of 700°C in order to limit the amount of lattice damage. The fraction of nuclei experiencing a large electric field gradient was considerably improved after two successive annealing sessions at 1200°C, from 1.0(0.6)% before annealing to 4.5(0.8)% after 6h and to 11.3(2.0)% after 162 h annealing. The electric field gradient for Re in HOPG is deduced to be Vzz = +5.4(2.6)·1022V/m2.