Waterborne GPR survey for estimating bottom-sediment variability: A survey on the Po River, Turin, Italy

We conducted an integrated geophysical survey on a stretch of the river Po in order to check the GPR ability to discriminate the variability of riverbed sediments through an analysis of the bottom reflection amplitudes. We conducted continuous profiles with a 200-MHzGPR system and a handheld broadband EM sensor.Aconductivity meter and a TDR provided punctual measurements of water conductivity, permittivity, and temperature. The processing and interpretation of the GEM-2 and GPR data were enhanced by reciprocal results and by integration with the punctual measurements of the EM properties of the water. We used a processing flow that improved the radargram images and preserved the amplitude ratios among the different profiles and the frequency content at the bottom reflection signal.We derived the water attenuation coefficient both from the punctual measurements using the Maxwell formulas and from the interpretation of the GPR data, finding an optimal matching between the two values. The GPR measurements provided maps of the bathymetry and of the bottom reflection amplitude. The high reflectivity of the riverbed, derived from the GPR interpretation, agreed with the results of the direct sampling campaign that followed the geophysical survey. The variability of the bottom-reflection-amplitudes map, which was not confirmed by the direct sampling, could also have been caused by scattering phenomena due to the riverbed clasts which are dimensionally comparable to the wavelength of the radar pulse

Analisi di deformazioni con metodi GPS

Ph.D thesi

An integrated GPS and Total Station instrument for cultural heritage surveying: the LEICA SmartStation example

Total stations and GPS receiver are normally used separately for terrestrial survey of cultural heritage, and the natural development has been the production of a single instrument where both a GPS and a total station work together. Several problems, such as the different reference systems used by the two techniques, require a geodetic approach to solve them. Leica Geosystems was launched SmartStation, an innovative product that integrates a GPS double frequency receiver and a Total Station series 1200. The real integration is obtained from a new firmware that is able to manage and store both kinds of measurements: angle and distance, RTK and other GPS observations. The GPS observations are functionally to the reference system set-up, while total station measurements provide the north direction of the reference system, and carry out a detailed survey using celerimetric measurements. A new instrument implies a new survey methodology, compared to classical techniques. Several survey scenarios can highlight the main advantages, that is no control points are needed, and there are no long traverses, or resections. To evaluate these new technologies and compare them with traditional ones, a case study survey has been conducted on the Porte Palatine, an archaeological building site in Turin, where a topographic referenced network was signalized and measured. The comparison focused on the time-saving, the staff needed to conduct the survey (skilled and/or unskilled), and the easiness of the survey operations