5 Steps to Successful Thermographic Mapping

  1. Accurate study of the object to be mapped, based on the project objectives

    1. An accurate analysis of the object to be examined is of key importance in successfully mapping with a UAS. In the visible sphere there are any number of sectors in which a thermal camera can be used: territorial surveys, inspections of buildings and urban areas, historic structures and monuments, plus an infinite variety of other scenarios. Each of them, in turn, can present a wide range of technological facilities that are often the primary focus of the inspection: photovoltaic panels, power-line stanchions, surfaces that disperse energy in the power industry, wall outlines and internal structures, surface defects in general, humidity etc..

    2. Each of the subjects of the subsectors described above presents its own unique features and peculiarities, which need to be closely analysed, in order to maximise the precision and effectiveness of the mapping and the subsequent use of the data, with priority given to identifying the best possible equipment and sensor for obtaining meaningful data. Here too, as in the field of the visible, or when operating with other electromagnetic bands, it is of no small importance to remember that not all mapping operations can be carried out a second time, due to any one of a variety of secondary conditions (involving the weather or the environment, or, in the case of plants, shut-downs of operations etc.).

    3. The planning of mapping is also of key importance in all instances where flight constraints (i.e. operations in critical settings) place limits on the time and space available for flying, or where the acquisition of photos and videos is subject to physical constraints (i.e. the inclination of photovoltaic panels; systems protecting against lightening; the façades of buildings found on narrow streets or in crowded squares that can be partially isolated; industrial plants whose tubes and pipes are in close proximity to each other etc.)

    4. A study of the purpose of the mapping is equally important (for design, survey, comparison, study, monitoring etc.), seeing that only in terms of the ultimate objective can we determine the best possible way to calibrate the mapping of the data in the field, so as to produce the output that is sought and required.

  1. Determining the mapping activities

    1. The first task is to list all the equipment and systems to be monitored: in many company settings, such a list is already available, and all that needs to be done is to eliminate the elements not suitable for thermographic inspection from the list.

    2. Next the items on the list should be ranked in terms of importance. Most companies have maintenance and production registers that show which equipment is more susceptible to malfunctions and thus needs greater attention. The registers also take into consideration the direct consequences of the malfunctions: equipment of critical importance must be monitored more frequently, and more closely, than other items that can be temporarily taken out of operation without causing the entire process to shut down; based on this information, the planning can be drawn up for thermographic inspections.

    3. If there are no registers available, or if they are missing information needed for performance of the mapping, then the request for thermographic mapping is the first step in the process of creating a maintenance and production register.

    4. But it is still not time to begin the inspection, as another key phase must be considered before it can get underway.

  1. Defining the reference parameters for the inspection

    1. Before the problems observed on the devices inspected can be diagnosed, reference materials must be obtained. It is highly advisable, therefore, that thermal images of all these devices, in the course of their normal operations, be obtained. In some cases, it may prove necessary to obtain a number of thermal images for a given device, especially if the device contains key components or subsystems susceptible to malfunctions. These images will be used as a basic reference framework, and so their procurement is of fundamental importance in preparing the best possible documentation for the inspection activities.

    2. Care must also be taken to account for all the factors mentioned in the manuals for the setting and the use of the thermal camera mounted on the UAV, so as to ensure accurate temperature measurements.

    3. The report on the inspection reference parameters must include the methods utilised, such as the settings for the emission and reflected-temperature levels of each device, as well as a precise description of the position of each thermal image.

    4. Once a benchmark database of images has been obtained, the acceptable temperatures for each device can be obtained and an alarm threshold can be set, so that the thermal camera will trigger an alarm whenever any area of the thermal image presents a temperature out of line with that established as the reference parameter (within a margin of tolerance), meaning that future inspections can be performed more rapidly and within a more fully developed context. It is always a good idea to record the alarm temperature for future use.

  1. Starting the inspection

    1. When all the reference temperature measurements have been performed, and adequately documented, the inspection of the plants and devices can begin, based on the register indicating which devices and plants should be inspected, as mentioned earlier.

    2. It should always be remembered that the operator of the thermal camera must possess a thorough understanding of both the physics of thermographic technology and the principles of operation of the device or plant being inspected, in order to be able to carry out a correct analysis generating data that can be used to predict failure. When inspecting a photovoltaic field, for example, an in-depth knowledge of the parameters governing the thermal camera for such devices is necessary, together with an equally solid knowledge of the principles of operation of the solar panels, so as to be able to correctly determine the amount of sunshine needed to highlight hotspots. The first piece of advice, therefore, is to immediately become well versed in all the reference temperatures tied to malfunctions of the plants or devices being inspected.

    3. In preparing for the flight, however, there is a whole series of secondary parameters that must also be obtained, seeing that they too could affect the thermographic mapping, meaning that: The starting time of the mapping should be recorded – the position of the Sun on the horizon should be observed, to avoid direct reflection of its rays (control of the recording angle and height) – the climatic conditions should be registered, with annotation of the temperature, relative humidity, speed and direction of the wind – evaluation with a meter measuring the Sun’s radiation, taking note of the time of the start of the trial - … - recording of any variations in environmental conditions - noting the time of the conclusion of the mapping.

  1. Analysis and Report

    1. When all the mapping has been completed, and the facilities have been inspected, it is time to go back to the office to analyse the images and draw up a report.

    2. The drafting of the report, based on the analysis of the data collected, makes it possible to accurately illustrate the thermal performance of the device over time, with graphs and tables that are easy to interpret. This information will be of help in foreseeing when maintenance is needed, as support for sufficient and effective planning.

    3. Contrary to what is advisable in the realm of the visible, it is not always a good idea to carry out redundant mappings, obtaining more images than would normally be considered necessary under standard practice, and this on account of the quantity of information found in each pixel of the thermographic image. Therefore, the planning of the mapping, along with knowledge of how the devices to be inspected operate, plus a precise awareness of the objective of the final report, are all key, synergistic elements when it comes to determining the right amount of information to be obtained in the field in the course of the UAV flight.