LABORATORIO CNR ISPC

                                                                    

NAME OF THE INSTRUMENT

Camere fotografiche ad alta risoluzione e diversi obiettivi; SAPR;  sistemi a scansione laser (TOF e phase-based), sistemi topografici (GPS differenziale e stazione totale) e sulle piattaforme GIS più comuni (QGIS)

 

GENERAL DESCRIPTION

The CNR ISPC laboratories have a strong know-how in survey methodologies and techniques integrating image-based e range-based finalizzate al rilevamento del patrimonio culturale, documentazione e visualizzazione scientifica. I laboratori sono dotati in particolare di strumentazione e sensori attivi e passivi per la digitalizzazione 2D e 3D di monumenti e siti archeologici. Il laboratorio è dotato sia di una stazione totale laser sia di uno strumento GPS in grado di lavorare in modalità differenziale. La strumentazione d’istituto consiste principalmente in sistemi fotogrammetrici terrestri ed aerei (camere fotografiche ad alta risoluzione e diversi obiettivi, SAPR), sistemi a scansione laser (TOF e phase-based), sistemi topografici come il GPS differenziale, per il posizionamento di punti sul territorio, intesi sia come punti di stazioni fisse per la costituzione di poligonali, sia punti per la determinazione della forma del territorio, che possono essere caricati direttamente sulle piattaforme GIS più comuni (QGIS), e stazione totale. Nel contesto di un progetto rilevamento 3D, il CNR ISPC può offrire la propria collaborazione scientifica per la pianificazione, rilevamento, elaborazione, interpretazione e visualizzazione dei dati rilevati.

 

TECHNICAL DESCRIPTION

Although laser scanner and photogrammetric systems are independent, they often require a topographic survey to support orientation and to avoid rotation and propagation errors. Given that, surveying activities on the territory or in the archaeological/architectural field are always carried out with the following instrumentation: Total Station (TS) and Global Navigation Satellite System (GNSS).

a)   The stazione totale can be considered the descendant of to the theodolite and is still a useful tool for topographic work in the archaeological field. Starting from different stations, defined by the topographer, it is possible to acquire coordinates of points in space, in a local reference system established a priori (x,y,z). In the past, this technique has made it possible to acquire numerical data in photo-rectification processes for the representation of the facades of historical buildings in the architectural field. Recently, it is a fundamental tool for every photogrammetric application. Indeed, topographic survey of ground control points is always required to improve photo alignment during image-processing and to scale and geo-reference 3D models obtained.

b)     GPS/GNSS (Global Positioning System/Global Navigation Satellite System) systems are measuring instruments used to gather and manage spatial data. This technology was developed at the end of the 1980s with the GPS constellation derived from military know-how . Currently, GNSS systems have achieved high accuracy in the field of topographic surveying by exploiting other constellations, such as GLONASS and COMPASS. The main advantage of this technology is the possibility to relate spatial data within a single (global) reference system.

GPS determines the coordinates of a point based on information received from at least 4 satellites, using the geometric principle of space forward intersection. A single GPS receiver has positioning error between 10 m and 30 m. This uncertainty depends mainly on the signal but also on other variables such as the geometric arrangement of the satellites. To achieve centimetre accuracy, it is necessary to use two receivers in differential mode. This mode, called D-GPS (Differential Global Positioning System), allows twin receivers (with the same characteristics) to receive the same information from the satellites at two different times during the measurement, improving final accuracy.

 

Referents:
Daniele Ferdani daniele.ferdani@cnr.it
Andrea Angelini andrea.angelini@cnr.it

 

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