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Digitisation of roofs for self-consumption installations

Technological development has brought the introduction of new methods and equipment for data collection, such is the case of industrial surveying, the use of the drone has come as an innovative tool to significantly reduce the time in which a job is performed, the number of staff, and the cost.

The photographic survey is the initial stage prior to the installation of photovoltaic panels for self-consumption. It is a technical analysis of the space where the installation is to be carried out, taking into account the dimensions, physical and geographical characteristics of the site.

Traditionally, this survey is carried out with tools such as Total Station and GPS, also the use of satellite images became popular in the topographic field because it presented a lot of advantages in the time of completion of the work. However, in recent years a new tool has been introduced to the world of topography, which promises great advantages and that is the drone.

Photographic surveying using a drone (photogrammetric surveying) and its advantages

Photogrammetric survey is the process of planning the flight of a drone, with ground support points to ensure greater accuracy, over the area of interest, in this case an industrial rooftop, using dedicated software and then executing it in order to obtain a collection of images that have a high overlap between them, 85%-85% minimum, which are subsequently used for the creation of an orthomosaic or plan.

When flying, it is important to make sure that in our project we have created enough points at the different levels of the roof, as, in addition to the images from above, we want to obtain enough oblique images with a high overlap, in this way we will also be capturing the sides of the different levels or elements of the roof and thus be able to calculate their height later on in the plan, anticipating the possible shadows that they could cause on the panels.

This final orthomosaic of the space is a high quality geo-referenced image that allows us to evaluate the area with great precision, recognise details, and estimate volume and dimensions. Once all this information has been obtained, it can be exported to a design programme, such as AutoCAD, to create the planimetry of the industrial roof.

Image 1. Three-dimensional orthomosaic of an industrial roof

Among the main advantages of using drones to carry out this type of project compared to using traditional methods alone are mainly access to more data and accuracy of detail, reduced cost, labour and time. This translates into efficient results achieved in less time and at a significantly reduced cost.

Well, you may be wondering about the difference between an orthomosaic made from a series of images captured by a drone and a satellite image, which can also be used to calculate the dimensions and to obtain the characteristics of the roof. 

And to answer this we have a picture that says more than a thousand words.

Image 2. Comparison between a drone orthomosaic and a satellite photo.

As can be seen in the previous image, the quality of detail is much greater in the photogrammetric survey carried out with a drone and this is the main advantage because it allows us to obtain the dimensions of the space with greater precision, which we will later calculate. As well as the characteristics of the roof, such as the waters, elements in relief, ventilation systems, light inputs, among other data, all of this necessary for the subsequent planimetry and planning of the installation of the photovoltaic panels. 

In the satellite image, we do not obtain the same level of detail and the information of the industrial roof ends up being very reduced, limiting us in the subsequent planning of the installation of the photovoltaic panels and possibly decreasing the efficiency of these in the long run due to errors made during the installation due to the lack of necessary information from the plan.

The same image was then enlarged for greater accuracy of detail and this is the result:

Image 3. Detailed comparison between a drone orthomosaic and a satellite photo.

Drawing up of the planimetry for the self-consumption installation.

Once the photogrammetric survey has been carried out and the images have been processed to obtain the orthomosaic of the roof, the next step is the creation of the plan of this same roof using the orthomosaic as a reference.

The plan is carried out by means of a digitalisation of the orthomosaic that allows us to identify the areas of interest on the roof, the elements that could shade the photovoltaic panels once they are installed, and the dimensions of the entire space. This digitalisation is delivered in an AutoCAD file (.dwg) where the design of the installation can be carried out later.

Let us also look at the digitisation of a roof that we have selected:

Image 4. Orthomosaic and digitisation of the orthomosaic.
Image 5. Detail of the orthomosaic with the measurements taken in AutoCAD.

This editable file is layered, so you can access the individual information you need, or the complete roof information. As in this example below:

Image 6. Modifiable layers in AutoCAD.

The planimetry based on a photographic survey carried out with a drone speeds up the work, obtaining the results sooner and without the need to send engineers to the roof, preventing any type of accident. Having an initial design that provides accurate and precise information avoids later changes and expenses that in turn delay the installation.