What is an orthophotomap and why it disrupts construction tracking?

What is an orthophotomap and why does it disrupt construction monitoring?

Construction is a complex process that requires precise planning, supervision, and coordination of activities. For investors and contractors, monitoring the progress of construction works is extremely important. Accurate tracking of progress allows for effective project management, identification of possible delays, checking the correctness of the project, detecting of potential shortages of materials, and ensuring the safety of employees on the construction site.

Nowadays, we have tools at our disposal that can greatly facilitate the process of monitoring the progress of construction works. One such tool is an orthophotomap.

Orthophotomap

An orthophotomap is a highly accurate representation of the photographed surface of the Earth, obtained from aerial or satellite images. In the case of images acquired from UAVs (Unmanned Aerial Vehicles), a resolution of 1 pixel per centimeter can be achieved, which means that each pixel of the orthophotomap represents a 1 cm^2 area.

A distinctive feature of an orthophotomap is that it preserves all the information from the images while simultaneously reproducing planar coordinates through georeferencing. Its unique characteristic is that it eliminates geometric deformations of photos caused by changing the perspective or slope of the terrain. This makes the resulting orthofotomap equivalent to how the area would be seen from a great height. Thanks to these features, the orthophotomap is an extremely useful tool for observing changes at a construction site with full con?dence that they accurately represent the observed area, maintaining orthogonal projection and scale.

How it is made

An interesting topic is how an orthophotomap is created. The input to the algorithm are photos with information about the spatial position and the location of the aircraft device at the time of taking the photo. Using this information, the algorithm obtains information about the approximate coverage areas of each photo, and in these areas, tie points are searched for. These tie points are pixels that represent the same point in space but on different images. Then, using the Structure from Motion algorithm, a point cloud composed of these key points is created. The ?gure below roughly illustrates the concept behind creating a point cloud using the SfM algorithm.

The obtained point cloud allows for precise alignment of the images relative to each other. The matched and aligned images are then combined to produce a map that looks like a photograph taken from a bird's-eye view perpendicular to the ground. An illustration of this process can be seen below.

Why is it used?

One can wonder why the use of an orthophotomap in the process of tracking the progress of construction works is so groundbreaking. Nowadays, much attention is paid to process automation, which is faster, less costly, and more easily scalable compared to manual work. The answer to these needs is the use of AI to analyze the progress of construction works. What does this use look like in practice?

Let's imagine that the investor wants to know how many of the solar piles have already been installed, and whether their assembly is in accordance with the design. In the standard supervision process, a surveyor would have to be sent to count all the posts and roughly measure their location. There are thousands of such piles spread over multiple hectares of the construction site, such an inspection could take even several days. An alternative solution is to take pictures using a drone around the entire construction site. Then, these photos are processed by very advanced, fully scalable software, as a result of which, after a few hours, an orthophotomap is ready. From that moment, our company can use AI for analyses in the form of counting the bars. As the orthophotomap is georeferenced, the location of each column can be

simultaneously examined. Of course, during the construction process, the investor usually wants to know the progress of many KPIs, and the analysis of construction works using an orthophotomap is easily scalable, because having a view of the construction site, we have access to information about everything on the construction site.

Advantages

One of the undeniable advantages of this technology is the speed of creation. Due to the advanced, fully scalable software we use, we can produce orthophotomaps in an automated manner over areas of up to several hundred kilometers long, consisting of many thousands of high-resolution photos. After only a few hours of data processing, we have an orthophotomap ready, and we can immediately start analyzing the progress of construction works.

Thanks to the use of new technology such as UAV and orthophotomaps, we can revolutionize the construction industry through a completely new approach that provides very high accuracy and versatility of inspection. It allows us to automate processes, making them cheaper and even more e?cient. Another aspect is the use of cloud computing, thanks to which we are scalable, and therefore we can serve many clients simultaneously, processing data from tens of square kilometers in parallel.

Commited by?Adam Wisniewski ?&?Jakub ?ukaszewicz