Photogrammetry is the science and technology used to obtain a accurate representation of a area or object through photographic images interpretation. Photogrammetry can either be aerial or terrestrial. It allows us to create topographical plans, digital terrain or surface models in certain cases, georeferenced point clouds and orthophotomaps.
Formerly restricted to the military, drone use is now accessible to numerous civil applications. In our field, drones are a tool of great efficiency, in photogrammetry in particular. Equiped with high-resolution cameras and image processing softwares, we are able to conduct the 3D modeling of all kinds of areas, with centimeter level precision.
Drone use also frees us from the obligation to use baskets for the shooting of inaccessible areas. We are now able to film or shoot closely the object of our study in order to examine roof damages for example or disorders on inaccessible structures.
The processing of collected data allows us to create classified point clouds, orthophotos, digital surface models and in certain cases digital terrain models. This method is quite efficient, particularly for quarry surveys, because it saves a lot of time collecting data. If the area is vegetation-free, we will then be able to create a digital terrain model.
In order to conduct a photogrammetry project and achieve the results needed by the client, we need to take into account several parameters :
First of all, we need to evaluate the legal feasibility of the aerial survey project. Depending on this factor, the sensor will be embarked either under a drone, on a helicopter or on an ultra-light aircraft, flight constraints being different for each method.
Secondly and based on the clients objectives in terms of resolution and precision, we will define the flight and recording parameters of the project and report the intented flights to the authorities.
Once our shooting is done, we will proceed to the photogrammetric processing of the photos. The model our topographers will obtain through this processing will then be georeferenced.
Drone survey of an entire pipes laying worksite
The orthophoto combines both the precision of a plan and the high resolution of a photo.
Aerial survey allows the access of sensible, inaccessible, protected or dangerous areas without damaging the environment or endangering the surveying team.
The main inconvenient of photogrammetry is that its resulting model is based on the information present on photos, thus on the surface : if vegetation is present, nothing below it will be seen nor recorded. It is as such impossible with aerial photogrammetry alone to represent a digital terrain model : drone survey data must most of the time be completed with ground data in order to ensure the reliability of the results.
Our drones and sensors are renewed regularly to ensure that our surveyors always get access to the newest surveying tools on the market, in order to provide the most accurate results for our clients.
1 DJI Mavic 2 Pro and 1 DJI Phantom 3 Pro
A SONY Alpha 7R for high-resolution shooting from an ultra-light aircraft or helicopter
DJI Mavic 2 Pro
DJI Phantom 3 Pro
SONY Alpha 7R
High-resolution orthophoto of the West Port, Reunion Island
Focus on a portion of the orthophoto
High-scale aerial survey
Photogrammetric survey of large areas (about 370 acres) for the Grand Port Maritime de La Réunion (major port of Reunion Island).
Aerial photo survey conducted with a photo sensor embarked under a helicopter. Record drawing of ground points spread out across the worksite. Photogrammetric processing conducted with the Agisoft Metashape software. Model rendered as an orthophoto. 7 cm / pixel resolution on the ground, with a 5 cm precision.
High resolution orthophoto compiled with the coordinates system, then purposely degraded and cropped to ease its further use. It can now be exploited with SIG or AutoCAD softwares.
East and West Port sections, Reunion Island
Drone survey of the concrete structure of an active building (1/2)
Drone survey of the concrete structure of an active building (2/2)
Monitoring of roof inaccessible areas integrity
Close-up shots of inaccessible objects or areas without basket use.
Drone use is a great solution to get around any access constraint and to obtain high-quality photos in inaccessible areas, allowing us to highlight any unseen structural damage.
In this case, we took pictures of concrete pillars, allowing the project owner to highlight damages and to act accordingly for the safety of all.
Drone survey of an entire pipes laying worksite (1/2)
Drone survey of an entire pipes laying worksite (2/2)
Work in progress monitoring
At the request of the pipe laying project owner, a video shooting was conducted monthly on the 3 kilometers worksite in order to assess the works advancement.
Compiled flight videos
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