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Scatter plot of diurnal difference and diurnal mean for midday and predawn of actual thermal DN values of deep cave (red), shallow cave (green) and surface control sites (blue). DNs = digital numbers. 

Scatter plot of diurnal difference and diurnal mean for midday and predawn of actual thermal DN values of deep cave (red), shallow cave (green) and surface control sites (blue). DNs = digital numbers. 

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Conference Paper
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Introduction: Since Rinker’s [1] groundbreaking work on terrestrial cave detection nearly 50 years ago, our ability to find caves using airborne and spacecraft acquired imagery has improved considerably. Due to superior analytical techniques, improved instrument optics, and high resolution imagery, we have furthered terrestrial cave detection capab...

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Context 1
... caves using the actual thermal of predawn imagery. Because this result occurred only once, we interpret it cautiously. Our limited ability to detect differences between deep and shallow features may be due to a small sample of shal- low caves (n = 4). Based upon this limited sample, these features exhibit thermal behaviors similar to deep caves (Fig. 2). Further, this result may be due to limita- tions in our seven point DN extraction method. While this systematic approach appears successful overall, it may be affecting the results by limiting the DN values analyzed for each feature. Most of the cave entrances were either crescent (lateral entrances viewed at nadir) or oblong in ...

Citations

... On Earth, caves are found by a combination of geological and geomorphological map analyses and their direct reconnaissance in the field (e.g., Ground Penetrating Radar). More advanced, albeit still somewhat experimental techniques, include combining thermal and visible imaging (e.g., Rinker, 1975;Cushing & Okubo, 2017;Wynne et al. 2015). These techniques should be fully developed and expanded upon to detect caves on other planetary bodies. ...
... The first groundbreaking work on terrestrial cave detection using airborne and spacecraft acquired imagery was made by Rinker [7] nearly 50 years ago. Wynne et al. [8] presented analytical techniques, improved instrument and high resolution imagery of terrestrial cave detection and confirmed cave-like features on other planets. Cave detection is typically most successful when multiple thermal images are acquired during both the warmest (mid-afternoon) and coolest (predawn) times of the day. ...
... The main method used in this research is detecting cave entrances by thermal cameras. This includes thermal ground imaging with high thermal resolution of long distances to detect caves (figure 2,7,8,9). This technology is important because it is the core of the research. ...
... All the necessary technologies for the first part of the research are currently evaluated with excellent results. 8 We surveyed the location of new unknown caves using this technique. For this purpose, we studied three pilot regions with great potential for locating new caves: ...
Article
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This work aims to create new scientific knowledge by developing new innovative technology for remote detection of unknown underground cavities and deep-seated rockslides. To achieve the goal, we intend to develop new innovative technology for remote localization of unknown underground cavities and deep-seated rockslides using a thermal camera mounted on a unmanned aerial vehicle (UAV). Technology is a defined sequence of operations and procedures under optimal conditions, varying within certain allowable limits, resulting in obtaining a particular result or product that meets certain requirements. Therefore, the development of new technology involves determining the allowable limits of deviation of the optimal conditions of operations and procedures for producing a good result that meets the established requirements. The development of new technology also involves determining the limits of its applicability under different external conditions. This paper includes determination of the allowable limits and the limits of applicability of the new technology being developed. Until now, no technology has been developed for remote detection of unknown underground cavities or deep-seated rockslides. The goal of this work is the development of such innovative technology with numerous applications in construction, environmental studies and protection, security, defence and infrastructure.
... Consequently, cave entrances can show a thermal contrast with respect to surface temperature, thus becoming potentially detectable by means of thermal infrared (TIR) cameras, especially when the temperature contrast between cave entrance and surface is greater (Wynne et al., 2008). This thermal contrast has been used to detect large caves through thermal remote sensing techniques (Rinker, 1975, Wynne et al., 2015 even as far away as Mars (Cushing et al., 2007(Cushing et al., , 2015Wynne et al., 2008). Nevertheless, airborne and satellite thermal remote sensing has typical spatial resolution of meters to hundreds of meters (Calvin et al., 2005;Küenzer et al., 2013) due to their flying height, being therefore unsuitable to spot most karstic cave entrances. ...
Article
Caves are buried geological features of great scientific and engineering interest. Based on the well-known thermal inertia of cave settings with respect to the surface, we have tested the use of thermal infrared (TIR) cameras carried by unmanned aerial vehicles (UAVs) to identify and characterize shallow karstic conduits. A pilot area was selected in a limestone rock massif from the Betic Cordillera (Southern Spain). At surface, this area appears as a doline field with several explored shaft entrances. The main and deepest shaft was thermally monitored at different depths, showing two well defined seasonal stages: (i) air and temperature stratification in summer and (ii) upward air flow and temperature homogenization in winter. We carried out UAV surveys at the expected maximum thermal contrast hours, finding out that winter dawns yielded the most distinctive images. These images show new warm air exits (warm spots) apart from the known cave entrances, and emphasize some of the main entrances depicting large warmed areas around them, which, in turn, can be related to shallow voids and conduits in the cave system. Furthermore, TIR images have been georeferenced using a network of identifiable points that can be transferred from visible orthoimages. The resulting TIR orthoimage mosaics have allowed us to define a number of quantitative parameters to characterize the warm spots. The most important of these parameters are: (i) the characteristic temperature, which is the maximum significant temperature of the air escaping from cave openings; (ii) the warmed area, which is the area that appears on the TIR orthoimage with a temperature greater than the surface temperature mode; and (iii) the average temperature weighted to the affected area. The georeferenced TIR orthoimages and the derived parameters are a new and very valuable tool for both speleological exploration and engineering purposes.
... Conference participants also discussed novel techniques for detecting planetary caves. Colleagues and I presented on how to apply terrain analysis techniques used on visible spectrum imagery to identify caves within thermal imagery [22]. We also proposed a roadmap for planetary cave detection using remote sensing. ...