International cooperation and technology transfer

Fras, Mojca Kosmatin

Bibliographic data

Monograph

Persistent identifier:: 856490555

Author:: Fras, Mojca Kosmatin

Title:: International cooperation and technology transfer

Sub title:: Ljubljana, Slovenia, February 2 - 5, 2000 : proceedings of the workshop

Scope:: VI, 163 Seiten

Year of publication:: 2000

Place of publication:: London

Publisher of the original:: RICS Books

Identifier (digital):: 856490555

Illustration:: Illustrationen, Diagramme

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: RTK SURVEY USING COMBINED GPS+GLONASS L1/L2 CARRIER PHASES. Crocetto N. - Gatti M. - Marchesini M. - Negroni F. - Russo P.

Document type:: Monograph

Structure type:: Chapter

41 Hood Section b ~ 13 m Fig. 9. Transverse section of the road embankment. The GPS+GLONASS RTK survey consisted of: • repositioning the planned sections on the ground, during the various repetitions; • measuring their variations. The measurements were taken twice a week for six months. The bi-weekly survey of a road embankment was performed in this way. The operator positioned the Master receiver on a vertex of known co-ordinates and initialised the Rover receiver, with a standing time of no more than one minute. At that point, he performed the operation of plane calibration: within the GPS reference system, he measured the co-ordinates of at least five points on the ground which had co-ordinates known also in the local system. When the double set of co-ordinates was entered into the CDU-2, the parameters of the plane calibration for passage from the GPS+GLONASS co ordinates to the local ones were calculated (Fig. 10). The maximum differences in the calibration were never greater than 5 cm. Fig. 10. Display of the Field Face Program in the CDU-2. When the parameters of the calibration and the planned co-ordinates of the sections were stored in the data logger, the operator proceeded with the measurement of the points in transverse directions. During the measurement operations, the acquisition interval of the single receivers was set at 1 sec and the minimum cut off of the satellites at 5°. The survey of a single road embankment, including the operations of repositioning, lasted from 1.5 to 2 hours. In this time period, 15 to 20 sections were measured, i.e. 300 to 500 points. The number of visible satellites was never less than 12- 13: on average 8 GPS and 5 GLONASS. The PDOP was never greater than 2. In this way, it was sufficient to stay with the Rover receiver on the survey points for no more than two epochs of measurements (Fig. 7 and 8). The same survey was performed with equipment similar to the previous one but with receivers for only GPS measurements in double frequency L1-L2 (GPS RTK). The sampling interval was the same (1") and the cut off was increased from 5° to 10°. With this equipment, the interruptions of the signal were more frequent, especially in correspondence to the scarps of the road embankments which reach considerable heights and inclinations (Fig. 9). The number of dynamic re-initialisations was increased and with them also the respective times of static (of initialisation and of a single fix) and dynamic stationing. Moreover, to permit the Rover device to receive many satellites and therefore to record the position, we were often forced to leave the area of measurement, with a considerable increase of the difficulty of surveying. From the operational point of view, the experiment showed: • the considerable capacity for acquisition of the GPS+GLONASS RTK system, especially in conditions particularly unfavourable for reception of the signal, e.g. during the survey of scarps or the calibration on vertices situated near electric power lines; • the good reception of the radio link signal from the Master to Rover, which never suffered interruptions that might compromise the execution of repositionings and fixes; • the reduced times of static initialisation and dynamic re-initialisation; • the good planimetric and altimetric precision, always within the tolerances established by the client; • the limitations of the GPS RTK system, both in the phase of initialisation and the phase of acquisition. Table 1 shows a comparison of the measuring times and number of operators employed in the two satellite techniques, as well as in the survey with an integrated theodolite, for an equal number of points measured (300- 500). It can be seen that productivity was increased by about 30% with respect to the traditional instrumentation, while the presence of operators was reduced to the minimum (only 1 GPS or GPS+GLONASS operator versus 1 theodolite operator + 2 rod holders). Measuring techniques Measurement time (minutes) Operators Integrated theodolite 240-300 3 GPS RTK 120-180 1 GPS+GLONASS RTK 90-120 1 Table 1. Comparison of the measurement times and the number of operators for the different survey methods. 2.2 Localising reference points in woodland for a water supply tunnel The second application involves the checking of the co ordinates of some vertices of an axis network for the organisation of the course of a water supply tunnel. These vertices are situated in an inaccessible wooded area,

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