Infrared exploration of the architectural heritage: from passive infrared thermography to <em>hybrid</em> infrared thermography (HIRT) approach

Abstract

Up to now, infrared thermographic approaches have been considered either passive or active. In the latter case, the heat flux is historically attributed to a non-natural heat source. The use of the sun has recently been incorporated into the active approach thanks to multi-temporal inspections. In this paper, an innovative hybrid thermographic (HIRT) approach is illustrated. It combines both the time component and the solar source to obtain quantitative information such as the defect depth. Thermograms were obtained by inspecting the facade of the Santa Maria Collemaggio church (L'Aquila, Italy), whereas quantitative results related to the sub-superficial discontinuities were obtained thanks to the use of advanced techniques. Experimental results linked to passive approach (i.e., the mosaicking procedure of the thermograms) performed by selecting a set of historic churches are also included in order to explain, when and where, the hybrid procedure should be used. RESUMEN: Exploración infrarroja del patrimonio arquitectónico: de la termografía infrarroja pasiva al enfoque de la termografía infrarroja híbrida (HIRT).Hasta la fecha, los enfoques sobre la termografía infrarroja han sido considerados, o pasivos, o activos. En este último caso, el flujo de calor se obtiene a través de una fuente de calor no natural. El uso de energía solar ha sido recientemente incorporado al enfoque activo gracias a los estudios multitemporales. En este trabajo, se ilustra un enfoque innovador de la termografía híbrida (HIRT). Se combina tanto el componente de tiempo y la fuente de energía solar para recuperar la información cuantitativa así como la profundidad del defecto. Las imágenes térmicas se obtuvieron mediante el análisis de la fachada de la Iglesia de Santa María Collemaggio (L'Aquila, Italia), mientras que los resultados cuantitativos inherentes a las discontinuidades sub-superficiales se obtuvieron gracias al uso de otras técnicas avanzadas. Los resultados experimentales vinculados al enfoque pasivo (es decir, el proceso de mosaico de las imágenes térmicas) derivan de un conjunto de Iglesias antiguas, también incluidas en el estudio, a fin de explicar cuándo y dónde tiene sentido realizar un proceso híbrido.

Thermography data fusion and nonnegative matrix factorization for the evaluation of cultural heritage objects and buildings

“…The optimization uses non-negative least squares (NNLS) considering A and Y . Here, the input thermography data is the basis calculated by NMF optimised by two different GD and NNLS methods [18].…”

Inverse Contrast in Non-Destructive Materials Research by Using Active Thermography

“…The image sequence may be analyzed in the time domain or in the frequency domain. Since it is more difficult to detect inclusions in large-sized and massive members, they are less often investigated using this method [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. No experiment in which the time of recording thermograms is considerably extended until a thermal equilibrium between the tested element and the environment is reached.…”

Reconstructing the Roman Site “Aquis Querquennis” (Bande, Spain) from GPR, T-LiDAR and IRT Data Fusion

“…Infrared thermography (IRT) is a technique for measuring characteristics related to the thermal state of the materials, allowing for the detection of pathologies mainly on their surface [29], but also in the sub-superficial areas if they present a high influence on the thermal state of the object [30,31].…”