## 1 Introduction  
The evaluation of deformations in civil infrastructures or natural environments is normally assessed by the realization of very accurate three-dimensional (3D) models by means of a range of complementary geomatics techniques such as total stations, global navigation satellite systems (GNSS), photogrammetry, or laser scanning [1]. Nonetheless, each geomatic technique is affected by its own instrumental and physical limitations, especially when the monitored area is large and has a complex topography [2]. For instance, atmospheric refraction can severely limit the achievable accuracy in the distance and angular measurements, also in laser and image scanning [3]. Therefore, the integration of data, collected by different techniques, in a unique coordinate reference frame becomes crucial to producing consistent 3D models able to be used for overtime deformation monitoring purposes [4]. In recent decades, advanced monitoring technologies have spread and increasingly been used for the study and management of geological hazard and risk, which may compromise the state of preservation of civil infrastructure [5]. Monitoring actions are necessary to guarantee health and safety conditions by controlling the evolution of deformation patterns or detecting significant instabilities. In terms of spatial and temporal resolution, the improvement of geomatics techniques represents a significant achievement. These methods provide innovative tools in supporting mapping products and geological analysis required for assessment and evaluation. Accurate and fully geo-referenced 3D datasets can be used to characterize in detail structural and geological settings, as well as the geomorphology of a studied area. Geological applications, for example, geo-hydrological risk assessment, rockfall runout modellings, or slope stability analysis, can have a great benefit through non-destructive investigation. Where a topographic survey is based on limited distances (e.g., tens to hundreds of meters), it has historically been carried out with total stations. Although such method provides high accuracy and precision for the measurement of individual points, significant time is required to collect a sufficient density of data to produce rough landscape Digital Elevation Models (DEMs) [6]. Laser Scanning (LS) and Close-Range Photogrammetry (CRP) are state of the art techniques for acquiring dense and precise topographic data at the output detail, for accurate volume measurements or modeling. Accurate mapping and monitoring of lakeside reservoirs, as well as coastal areas and fluvial processes, are critical tasks to which several techniques have been used, from aerial photographs, remote sensing, land surveying, CRP and, more recently Terrestrial Laser Scanning (TLS) and Mobile Laser Scanning (MLS). These latter technologies are in principle advantageous because of their good accuracy, easiness of use and lower time of response [7]. Most of the existing geomatics techniques are sometimes unaffordable, and there is not an all-in-one solution able to provide spatial information with suitable accuracy and temporal frequency. For the completion of existing surveys in particular, MLS was considered the most suitable alternative for the challenges established in the project requirements, concerning productivity, sample density and final costs. In particular, Mobile Mapping System (MMS) technology enables users to reach complex and enclosed spaces, either scanning by hand or by attaching a scanner to a trolley, drone, or mounting on a pole. As a result, the variety of difficult-to-survey environments becomes wider. This solves the problem linked to GNNS-based systems where it does not work well in complex contexts, for example, woods, where tree canopies block signals, as occurred in this case study. With no reliance on remote data, MMS are a priori a truly go-anywhere technology. In this paper, a comparison of a long-range handheld MMS with the CRP has been evaluated that offers particular promise for site-scale topographic surveys.