Romania, due to its historical background, has many vestigial belongings to the cultural heritage, out of which the most noticeable (by number, age, architecture, symbolism and representation) are the wooden churches. Under these circumstances the role of the current study is to emphasize certain practical aspects (focused on the need to assess, preserve, restore and valorize) regarding the use of modern technology based on photogrammetry and 3D scanning. The case study was represented by the “Saint Martyrs Constantin Brȃncoveanu and His Sons” wooden church from Oradea Municipality, Bihor County, Romania; the edifice being included on the list of historical monuments ever since 2010. The final goal being to create 3D models for both the exterior and interior of the monument for research, restoration in case of need, sharing for education, entertainment, tourism purposes etc.

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Because of the dynamics of the GPS technique used in different domains like geodesy, near real-time GPS meteorology, geodynamics, the precise point positioning (PPP) becomes more than a powerful method for determining the position, or the delay caused by the atmosphere. The main idea of this method is that we need only one receiver -preferably that have dual frequencies pseudorange and carrier-phase capabilities -to obtain the position. Because we are using only one receiver the majority of the residuals that are eliminated in double differencing method, we have to estimate them in PPP. The development of the PPP method allows us, to use precise satellite clock estimates, and precise orbits, resulting in a much more efficient way to deal with the disadvantages of this technique, like slow convergence time, or ambiguity resolution. Because this two problem are correlated, to achieve fast convergence we need to resolve the problem of ambiguity resolution. But the accuracy of the PPP results are directly influenced by presence of the uncalibrated phase delays (UPD) originating in the receivers and satellites. In this article we present the GPS errors and biases, the zenith wet delay and the necessary time for obtaining the convergence. The necessary correction are downloaded by using the IGS service.

When using the PPP method, it is recommended to take into account the tropospheric influences for obtaining reliable estimates. Global Navigation Satellite System (GNSS) observations taken at low elevation suffer more strongly from atmospheric, antenna phase center variation and multipath effects, hence the observations are noisier than those at higher elevation angle, but they are essential to decorrelate the estimated station height and tropospheric zenith delay (ZTD). To relate the ZTD in the direction of an observation, the so-called mapping function (MF) are used. In this article the influence of different mapping function was studieds such as: Niell mapping function (NMF), Global Mapping Function (GMF) in conjunction with the Global Pressure and Temperature 2 -GPT2, Vienna Mapping Function 1 and no mapping function. The MF were used at different elevation cutoff angles -5 0 , 7 0 , 10 0 and 15 0 . The impact was analyzed: a) on the postfit residuals of the ionospheric free combination for phase (LC) and for pseudorange (PC), b) daily variability for North, East and Up component; c) evaluation of coordinates repeatability and how they are affected by the changes of the cutoff elevation angle and mapping function. The analyzed data was taken from 4 EUREF stations for a period of one month -October 2015. By using the VMF1 mapping function, the lowest value was obtained for the postfit residuals of the LC combination for all the stations. The difference in daily variation between each individual solution for the horizontal component is at the level of ~0.3 ÷ 0.5 mm, with smaller effect on the East component compared to North, whereas the Up component is at the level of ~1.0 ÷ 1.5 mm. The standard deviation (SD) is used as a measure of station position repeatability and the results suggested that for high precision determination a cutoff elevation angle of 10 0 should be used. Although at low elevation -5 0 and 7 0 -the VMF1 performs better than the GMF/GPT2 and NMF, after 10 0 the GMF/GPT2 is strongly in agreement with VMF1 and after 15 0 the NMF shows similar results as VMF1 and GMF/GPT2.

Due to the development of GPS technology, nowadays we are able to determine geodynamic plate motion around the world. Using an appropriate noise technique and understanding all the stochastic effects we are able to do a proper GPS time series analysis in which the sources of noise can be classified as: white noise, flicker noise and random walk. We study the area from the Caribbean Sea, taking the data from two GPS stations for a period of 7.5 years. We use spectral analysis and Maximum Likelihood Estimation. In the first part of the analysis we simultaneously estimate the velocity and amplitudes of the noise with integer spectral index and in the second part we estimate the spectral index. The noise model that presented the higher values of the log likelihood is a combination between power law and white noise which best describes the noise characteristics of all three components. In all the cases the noise amplitudes presented higher values for the vertical component. Also, the rate uncertainties for the power law plus white were higher by a factor of 10, then by using only white noise model. ARTICLE INFO