Orthophotography: Precision at the service of your projects
Introduction
Orthophotography is a technique that combines photography and cartography to produce georeferenced images with high precision. Used in many fields such as architecture, urban planning, heritage conservation, and engineering, it enables accurate visualization and analysis of spaces. In this article, we will explore what orthophotography is, how it works, its practical applications, and the benefits it offers for your projects.
What is orthophotography?
Orthophotography is a technique for producing aerial or ground photographic images that have been corrected to eliminate distortions caused by perspective and terrain topography. The result is an orthorectified image (orthoimage) that combines the visual richness of a photograph with the geometric precision of a map.
Origin and Evolution
- History : Orthophotography was developed by the French army in 1908 to create maps from photographs taken by airplanes. Since then, it has been adapted for broader use and has become an essential tool for many sectors.
- Evolution : With the advent of digital technologies, orthophotography has undergone a revolution. Images are now produced using data collected by drones, satellites, or airplanes equipped with high-resolution digital sensors and LiDAR systems. These technological advancements, combined with advanced processing software and global positioning systems (GNSS), have significantly improved the quality, accuracy, and resolution of orthoimages, meeting the needs of various sectors.
How does orthophotography work?
Capture Process
- Image Acquisition : Images are captured using drones, terrestrial scanners, or devices mounted on airplanes, following a precise protocol. Each photo must overlap to allow algorithms to identify common points and ensure full coverage of the area. The device's orientation must remain consistent, and lighting conditions uniform to ensure optimal image quality.
- Geospatial Data : Precise positioning (GPS) and orientation data are collected for each image. This data allows the photos to be georeferenced and properly aligned during processing.
Image Processing
- Assembly : Photos are assembled using photogrammetry software that detects common points between them to create a mosaic covering the entire area of interest.
- Geometric Correction : Mathematical models correct distortions caused by the camera lens, perspective from the shots, and terrain topography. This process ensures an accurate orthogonal representation of the surface.
Production of Orthophotography
- Final Image : The produced image, called an orthoimage, is orthorectified, meaning that distances, areas, and angles can be measured with high accuracy.
- GIS Integration : Orthoimages can be integrated into Geographic Information Systems (GIS) to perform in-depth analyses, such as mapping or urban planning.
Applications of Orthophotography
Architecture and Urban Planning
- Urban Planning : Assists in designing development plans by providing an accurate view of the terrain.
- Construction Monitoring : Tracks the progress of works with regular updates of orthophotographs.
Heritage Conservation
- Documentation : Accurate recording of the current state of historical monuments.
- Degradation Analysis : Identification of areas requiring restoration.
Engineering and Construction
- Preliminary Studies : Assessment of the terrain prior to construction.
- Volumetric Calculations : Measurement of material volumes to be moved.
Advantages of orthophotography
Geometric precision
- Reliable measurements : Ability to take precise measurements directly on the images.
- Error reduction : Elimination of distortions caused by perspective.
Visual richness
- Visible details : Visualization of terrain and structural features with great clarity.
- Additional information layer : Provides more details than a traditional map.
Accessibility
- Simplified sharing : Can be easily shared with project teams and stakeholders.
- Compatibility : Easily integrates with CAD software and GIS platforms.
Conclusion
Orthophotography is a tool that offers a unique combination of geometric precision and visual richness. Whether for architecture, heritage preservation, engineering, or agriculture, it provides considerable added value by facilitating decision-making.
