What is Photogrammetry?

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Explaining Photogrammetry

Photogrammetry is the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring, and interpreting photographic images. Photogrammetry is not a new technology, its principles date back to Leonardo da Vinci’s research on perspective in 1480. For centuries, photogrammetry has played a critical role in our understanding of objects far away from the Earth’s surface. Its uses have recently expanded to industries such as construction, engineering, architecture, agriculture, and more.

What is Photogrammetry?

Photogrammetry reconstructs objects or environments through the use of photographs. Site photos are taken from the air or ground with a high-quality camera, capturing images from different locations and angles. The data captured provides enough spatial detail to allow for accurate calculations. Once the visual data is gathered, the photos are stitched together to create real-world topographical maps, meshes, and 3D models. The technique can be used for construction engineering, military intelligence, agricultural assessment, and more.

The Meaning of Photogrammetry

When you break down the word photogrammetry – “photo” refers to light, “gram” means drawing and “metry” refers to measurements. Photogrammetry uses photos to gather measurements from which drawings, maps, and models can be created.

What Are the Types of Photogrammetry?

Aerial Photogrammetry

Taking aerial photos is one of the most common approaches to mapping out an area. Aerial photographs capture point-in-time visual records of specific land areas. The process entails mounting a camera on an aircraft or drone. Engineers determine the flight path and the number of photos the camera will take, based on the desired output and resolution. Aerial photogrammetry can capture hundreds of photos of a large-scale real-world environment, like a subdivision or city, in hours.

Depending on the goals of a project, teams can use aerial or drone-based photogrammetry to create photorealistic orthomosaic maps, capture valuable volumetric data or generate interior models for virtual home tours on real estate sites. Aerial photogrammetry tends to work best for large-scale, exterior projects.

Terrestrial Photogrammetry

Terrestrial photographic images are taken from a fixed position on the ground. Data about the camera’s position, such as its coordinates, are collected at the time the photo is taken. Terrestrial photogrammetry requires manual resources, and it may take longer to cover a large portion of land. When collecting photos, images need to overlap with each other, so they can be effectively stitched together to generate reliable site data.

Terrestrial photogrammetry is used to capture fine architectural details and are often collected with a laser scanner. A laser scanner captures photos of an environment and overlays the images on top of a point cloud, allowing for very accurate representation of the physical features of a site.

The Basics of Photogrammetry

Triangulation is the principle used by photogrammetry to produce three-dimensional coordinates. By mathematically intersecting converging lines in space, the precise location of a point can be determined.

What are the Advantages of Photogrammetry?

  • Fast data collection
  • Accurate, reliable data
  • Broad view of mapped area
  • Permanent records of existing conditions
  • Reduces the need to return to site
  • Easily captures hard to reach locations
  • Minimal disruption to environment

Photogrammetry for Engineering

The engineering industry has used photogrammetry to obtain accurate building measurements for many years. By using the 3D rendered images from laser scanners or drones, engineers can evaluate as-built site details and the progress of construction work. 3D rendered images can be used to create a 3D model or 3D mesh for evaluation and planning.

Photogrammetric Maps

  • Topographical Maps Shows the shape of the land and its elevations and contours.
  • Orthomosaic Maps – Offer a photorealistic representation of an area that can produce survey-grade hyper-accurate measurements of topography, infrastructure, and buildings.
    • Aerial Maps Photogrammetry can create maps out of aerial photos. It is cost-effective and accurate, allowing planning entities like architects, local governments, and general contractors to make clear, informed decisions about their projects without spending months scouring the landscape.

      Industries Using Photogrammetry

      • Civil Engineering – Photogrammetry documents the terrain to plan for urban development and roads
      • Structural Engineering – High accuracy photogrammetric images and models allow engineers to assess a site and plan for construction projects.
        • Military – For the military, photogrammetry can turn aerial imagery into accurate 3D surface maps in real time without any human oversight.
        • Agricultural Photogrammetry can be used to assess field conditions and detect crop or soil problems that might otherwise go unnoticed at ground level.
        • Film & Entertainment – The entertainment industry has started to rely on 3D models from photogrammetry for the virtual building of games and movies. 3D modeling can help bring the planned virtual worlds like cities and other historical places to life with accurate measurements.
        • Real Estate Drones and the technique of photogrammetry have been used by many real estate agents to create an accurate image of the house that they want to sell or rent.
        • Forensics Photogrammetry provides precise documentation of accident and crime scenes when presenting the case in front of the court.
        • Archaeology Overhead photogrammetry provides an opportunity to map surfaces to understand the structures and layout on an archaeological or excavation site.

        There are advances daily in the applications for photogrammetry. High resolution cameras, drones and LiDAR laser scanners continue to advance this technology and offer services for many industry needs.

        For more information on photogrammetry, contact TruePoint Laser Scanning at info@truepointscanning.com or 419-843-7226.