The course aims to describe the instruments, methods and operating procedures for the use of Unmanned Aerial Vehicle (UAV) for surveying purposes, using an approach based on images and Structure from Motion (SFM) techniques.
The use of traditional survey methods using topographic instruments (total stations, levels and GNSS receivers., Laser scanner), requires the presence on the ground of technicians and surveyors that are expensive and time spending. The UAVs allow to quickly acquire aerial images, limiting the presence of operators in the field.
Thanks to recent advanced methods related to computer vision and digital photogrammetry, the SFM techniques allow to efficient use aerial images captured by the drones for an automatic generation of:
• points cloud on the object, as made as laser scanning instruments;
• 3D spatial information useful for mapping;
• digital terrain models (DTM) and digital surface models (DSM);
• textured photorealistic 3D models;
• orthophotos, solid images (RGBD images) and solid orthophotos.

The tools and methods presented allow the students to have a knowledge for a wide range of applications such as for territorial and environmental surveys, for urban, cultural heritage and architectural aspects and for precision farming.

In this course, the students will learn:
• the technological aspects related to the drones and on-board sensors (for navigation and imaging);
• the theoretical aspects related to the use of images in order to acquire metric information;
• the design and operating procedures for planning the survey operations;
• the use of some available software (commercial and/or open source) to address the processing steps and generation of final products;
• metrical requirements (in terms of quality and quantity characteristics) for final products;
• a critical analysis about the surveying procedures and the obtainable results;
• national and international standards and regulations.

After attending the course, students will be able to:
• plan the UAVs acquisitions, considering scale and final products;
• process acquired data in order to obtain the final results;
• analyze obtained results in terms of precision, accuracy, completeness and level of detail, in a critical point of view.

The lab activities deal with the entire survey process realized by drones: flight planning for images acquisition, the flight planning, data processing to extract metric and radiometric information of objects, the generation of final products, depending on the different application area (land survey, urban, architectural and cultural heritage, precision farming) will be also considered.

Basic concepts about geomatics and/or surveying and basic sciences (mathematic, physics, ecc.).

The program is divided into 4 modules of lectures, for a total duration of 30 hours, and a series of practical exercises to be performed at both the LAIB, the Laboratory of Photogrammetry, Geomatics and GIS at the DIATI and the Laboratory of Geomatics for Cultural Heritage of DAD and flying field area.

Lessons (30 h):
Module 1: The Unmanned Aerial Vehicle
Definitions and state of the art, systems available, photogrammetric UAV approaches and some application examples.

Module 2: Structure from Motion
In this module are considered aspects about the measurement of real objects by means of digital images, the principles of photogrammetry and Structure from Motion in addition to projective geometry, digital camera images (radial and tangential distortions due to optics and sensor), the use of stereoscopic images, the calculation of the 3D structure with 2 images, the use of 3 or more images, the matching techniques (pixel, sub pixels by least squares, interest operators and features matching)

Module 3: The spatial information process using UAV
The survey process, planning activity, planning and implementation of autonomous flight, the use of Ground Control Points and Check Points, the surveying processing by aligning the images (external orientation), auto-calibration of digital cameras, generation of the dense cloud are considered.

Module 4: The final products generation
In this module are considered aspects about the generation of the photorealistic 3D model, definition and production of DSM/DTM, interpolation techniques, methods of generation and production of orthophotos. Description of possible applications in the field of land surveying, environment, cities, architecture, cultural heritage, the forest resources and precision agriculture are also taken into account.

Lab activities (30 h):
The lab activities take about half of the course and are focused on:

• Planning of photogrammetric surveys using UAVs and on the field acquisition;
• data pre-processing using commercial and/or open source softwaretools for the external orientation procedure;
• data post-processing for point cloud generation using commercial and/or open source software;
• final products generation: orthophotos, digital elevation model, 3D models (mesh and mesh with texture).

The works are carried out in team; finally, a special report with graphical drawings must be completed.
Some specicif activites will be developed according to the various degree programs in collaboration with other courses in the field of urban, architectural and cultural heritage survey (Building Engineering, Architecture), the survey of facilities and infrastructure (Civil Engineering, Architecture), the territorial and environmental survey such as river beds, landfills and other (Environment, Land and Infratructure Engineering, Urban Planning) and for precision farming.

The main text consists of the lecture notes provided by the teacher and slides presented during the classes.

The exam consists of three parts:
- Exercises made during practical activities on the entire process of acquiring spatial metrics information using UAV. The exercises is evaluated as vote/30.
- The capacity to process data acquired from UAV thanks to specific software tools, in order to extract spatial information. This part is evaluated as vote/30.
- Oral exams where is possible to evaluate theoretical aspects acquired during the course. This part is evaluated as vote/30.
The final grade is a weighted average of the results of the three previous tests.