Geoinformation Issues Vol. 7, No 1, 2015
Editorial pages, contents, reviewers of journal "Geoinformation Issues"
Walyeldeen Godah, Malgorzata Szelachowska, Jan Krynski
On the selection of GRACE-based GGMs and a filtering method for estimating mass variations in the Earth system over Poland
Abstract. Since the launch of the GRACE (Gravity Recovery And Climate Experiment) satellite mission in 2002, significant progress in the knowledge regarding the temporal variations of the Earth’s gravity field has been achieved. The main objectives of this contribution are to define a suitable filter to reduce the noise contained in the latest release, i.e. RL05, of GRACE-based GGMs as well as to select the most suitable GRACE-based GGM time series for estimating mass variations in the Earth system over Poland. The performance of the Gaussian filter with different radii and the de-correlation filters (DDK1–DDK5) applied to reduce the noise contained in those GGMs was examined. First, they were investigated globally. Then, they were examined over the area of Poland, in particular, over two basins, i.e. the Vistula river basin and the Odra river basin. Moreover, both the internal and external accuracy of RL05 GRACE-based GGMs were assessed. Error degree variances of geoid heights were calculated on the basis of these models. Equivalent water thickness variations obtained from GRACE-based GGMs were compared with the corresponding ones obtained from the hydrology model. The obtained results were analysed and discussed. Finally the filtering method and the GGM time series most suitable for estimating mass variations in the Earth system over Poland were selected.
Comparison of techniques for Integrated Precipitable Water measurement in the polar region
Abstract. Tropospheric delay estimates (tropospheric product) for selected International GNSS Service (IGS) and EUREF Permanent Network (EPN) stations made it possible to asses two areological techniques in the polar region (mainly in Greenland). Integrated Precipitable Water (IPW) – important meteorological parameter is derived from GPS tropospheric solutions by a known procedure for GPS stations. To convert from the wet part of tropospheric delay (ZWD) to IPW, the relation between 2 m temperature and the
so-called mean temperature of the atmosphere above was derived using local radiosonde data for nearby GPS stations. Sunphotometer data were provided by AERONET (NASA AErosol RObotic NETwork). IPW comparisons lead to the determination of a systematic difference between the techniques of GPS IPW and sunphotometer data (not present in the case of RAOBs). IPW measured by sunphotometer CIMEL (Cimel Electronique) is several percent smaller than IPW from GPS (both IGS and EPN solution). The bias changes seasonally and is a function of atmospheric temperature. It signals some systematic deficiencies in solar photometry as the IPW retrieval technique. CIMEL IPW shows some temperature dependent bias also in relation to radiosoundings.
Zbigniew Bochenek, Dariusz Ziółkowski, Maciej Bartold
Application of NOAA AVHRR satellite images for studying various environmental and climatic conditions in Polish forests
Abstract. The main objective of the presented work is to make an evaluation of the applicability of low-resolution satellite data for studying the condition of Polish forests being under impact of various climatic and environmental factors. NOAA AVHRR images were used in the work; vegetation indices derived from these images were combined with meteorological parameters obtained from weather stations. Six forest study areas representing different climatic and environmental conditions were used in the research work. The results of the study revealed that there are statistical relationships between remote sensing based indices derived for forest areas from low-resolution satellite data and temperature information characterizing climatic conditions, especially in the first part of the growing season. These findings were confirmed both in the spatial context – in various climatic zones – and in the temporal context.
Automated measuring devices for pendulum wire displacements
Abstract. The article describes the construction and principle of operation of two prototype devices: a laser device and an inductive device for measuring the pendulum wire displacement. A rotating laser beam and two inside detectors (fixed), as well as two external detectors were used in the first device. Falling on the detectors, the laser beam will cause them to generate electrical signals. The time differences between the signals generated by the internal (fixed) and external detectors are a function of the pendulum wire displacement. Inductive sensors mounted inside the measuring head, which is fixed to a cross-truck, moving along the perpendicular X and Y axes in the range of 50 mm, were used in the second device. The cross-truck is moved by stepper motors, and the inductive sensors placed in the X and Y axes search for the location of the pendulum wire. The number of steps of the stepper motors is a measure of the pendulum wire displacement along the X and Y axes.
Such devices are used to control the deviation of verticality of tall hydro-technical facilities mainly due to the action of internal stresses and external factors such as temperature and the water level in the tank.