**1. Introduction**

Mountain glaciers represent the main source of fresh water for human activities of the surrounding regions [1, 2]. Furthermore, glaciological processes (e.g. ice break-offs, glacier outbursts, snow/ice avalanches) can threaten population, urban areas and infrastructures [3]. In densely populated areas, such as the European Alps, the interaction between glaciers and anthropic activities is very frequent and it is of crucial importance to study the glaciers to understand their evolution and response to climate change, which is expected to reduce their area coverage and increase their instability [4].

Long-term monitoring of glaciological processes is often complicated and expensive, especially in remote areas and inaccessible terrains, which are common in mountain environment [5]. A practical approach is the adoption of remote sensing apparatuses that allow observing glacial processes with minimal risk for scientists and technicians. In recent years, the free availability of data acquired from satellite platforms has largely improved the possibility to observe wide areas from remote with relatively high spatiotemporal resolution. Nevertheless, satellite surveys suffer complex geometries and the revisit time might be not adequate to

measure fast processes. Therefore, the use of close-range remote sensing systems is often the most effective solution for glacier monitoring [6].

Section 2 presents a substantial list of close-range remote sensing techniques that can be adopted to measure glacier surface deformations. Section 3 is devoted to the Planpincieux and Grandes Jorasses glaciers (Mont Blanc massif) case study (**Figure 1**). In recent years, such a glacial complex has become an open-air laboratory where innovative and experimental monitoring systems have been developed [6–12]. Several practical examples of close-range remote sensing surveys will be described therein.

**Figure 1.**

*Overview of the Planpincieux and Grandes Jorasses glaciers (upper tile) and area of study (lower tile). Yellow and orange rectangles indicate respectively the Montitaz Lobe and the Whymper Serac framed by the time-lapse cameras (Figure 2).*

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*Close-Range Sensing of Alpine Glaciers DOI: http://dx.doi.org/10.5772/intechopen.92841*

**2. Close-range remote sensing techniques**

structure and thickness (**Table 1**).

**Figure 2.**

*onto the serac surface in 2019.*

**2.1 Point clouds for surface generation**

of different object hit by the same pulse [18].

The study of the Planpincieux and Grandes Jorasses glacier surface deformations has been conducted following different approaches: (i) volumetric changes have been evaluated with point clouds and digital elevation models (DEMs). Such measurements have been obtained with laser scanners or structure from motion (SFM) processing. (ii) Surface kinematics maps of specific displacement components, which have been provided by monoscopic time-lapse camera and terrestrial interferometric radars. (iii) 3D displacements measured in specific points with a robotised total station (RTS). Furthermore, helicopter-borne ground-penetrating radar (GPR) campaigns have been conducted to investigate the glacier internal

*(a) Image of the Montitaz Lobe of the Planpincieux Glacier monitored by a monoscopic time-lapse camera. The terminus width is approximately 100 m. (b) Image of the Whyper Serac acquired by monoscopic time-lapse camera. The serac face is approximately 40-m high. The black circles indicate the prism positions* 

Three-dimensional point clouds are crucial tools in glacier monitoring; the main survey techniques to obtain them are LiDAR [13], terrestrial laser scanner (TLS) [14] and aerial and terrestrial photogrammetry, particularly structure from motion (SfM) approach [15]. LiDAR and TLS are based on a sensor, terrestrial or airborne, capable of emitting laser pulses at high frequency and measure their 'time of flight' in order to compute the position of each echo. The absolute position of each point is calculated from the emitter centre, geocoded by a GNSS coupled with an inertial measurement unit [16]. Besides its coordinates, each point can be characterised by the intensity of the echo in order to detect the nature of the target [17]. By the exploitation of laser beam divergence, it is also possible to discriminate and analyse multiple echoes or even the full waveform, thus obtaining multiple measurements

Concerning SfM, it is a technique originating from computer vision, which, by processing multiple images from different points of view of the same target object, generates a three-dimensional point cloud. The algorithm matches common

#### **Figure 2.**

*Glaciers and the Polar Environment*

measure fast processes. Therefore, the use of close-range remote sensing systems is

Section 2 presents a substantial list of close-range remote sensing techniques that can be adopted to measure glacier surface deformations. Section 3 is devoted to the Planpincieux and Grandes Jorasses glaciers (Mont Blanc massif) case study (**Figure 1**). In recent years, such a glacial complex has become an open-air laboratory where innovative and experimental monitoring systems have been developed [6–12]. Several practical examples of close-range remote sensing surveys will be described therein.

*Overview of the Planpincieux and Grandes Jorasses glaciers (upper tile) and area of study (lower tile). Yellow and orange rectangles indicate respectively the Montitaz Lobe and the Whymper Serac framed by the time-lapse* 

often the most effective solution for glacier monitoring [6].

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**Figure 1.**

*cameras (Figure 2).*

*(a) Image of the Montitaz Lobe of the Planpincieux Glacier monitored by a monoscopic time-lapse camera. The terminus width is approximately 100 m. (b) Image of the Whyper Serac acquired by monoscopic time-lapse camera. The serac face is approximately 40-m high. The black circles indicate the prism positions onto the serac surface in 2019.*
